Anatech,
I don't know if your rant is about what I wrote but I think you should lower your voice.
What I advocate is to do what is safe and MAY produce some benefit. What I did not suggest is to "re-engineer" this amp. Or any amp that I did not design and know what it should do end to end. Second guessing an unknown intent is just plain silly.
The PA-7 was a good amp because it was an almost exact copy of a proven, successful design by Nelson Pass. He designed it, and Nakamichi "licensed" it. The major contribution of the Nakamichi - to me at least - was making it pretty. And I think they were successful in that regard.
However, what the Nakamichi "engineers" did not do was to build a safer, more robust amplifier without impacting its sonic performance. In fact, I would say they did not do what I would have expected competent engineers to have done. If they did, you would never have seen them under warranty. And plenty of them saw service under warranty.
Examples are the very poor PCB build quality; the shoddy way the rail voltages are conducted from the caps to the PCB; the exposure of key components to significant heat due to improper placement - these are NOT signs of good engineering, and when anyone with any electronic construction skills come across them, it is a good thing to know what can and should be improved, and not ignore them.
The value of the feedback cap is a peculiar implementation and that is a well-documented departure between the original Threshold design and the PA-7. The upgrading of the rectifier with a modern, faster, softer switching unit is perfectly safe and recommended. The replacement of dried out electrolytics with film caps where possible is also a well-regarded, safe and prudent practice.
My 2 cents about the PA-7 is that it is a beautiful amplifier to look at, and to me, it was worth the time and effort to make it sing again, perhaps even better by correcting some of the flaws I came across, and replacing outdated component with modern, more reliable ones. The original trimpots in the PA-7 were crappy 3-cent parts that replaced with a multi-tiurn Bourns helps tremendously in setting DC offset. This amplifier could have been much BETTER engineered and built but it was not.
So please help fellow forum member realize their amp's true potential with your knowledge and recommend specific, workable changes, including part numbers. Just telling others you never met that they "do not know more than the engineers who created these amps" is not helpful to anyone.
I don't know if your rant is about what I wrote but I think you should lower your voice.
What I advocate is to do what is safe and MAY produce some benefit. What I did not suggest is to "re-engineer" this amp. Or any amp that I did not design and know what it should do end to end. Second guessing an unknown intent is just plain silly.
The PA-7 was a good amp because it was an almost exact copy of a proven, successful design by Nelson Pass. He designed it, and Nakamichi "licensed" it. The major contribution of the Nakamichi - to me at least - was making it pretty. And I think they were successful in that regard.
However, what the Nakamichi "engineers" did not do was to build a safer, more robust amplifier without impacting its sonic performance. In fact, I would say they did not do what I would have expected competent engineers to have done. If they did, you would never have seen them under warranty. And plenty of them saw service under warranty.
Examples are the very poor PCB build quality; the shoddy way the rail voltages are conducted from the caps to the PCB; the exposure of key components to significant heat due to improper placement - these are NOT signs of good engineering, and when anyone with any electronic construction skills come across them, it is a good thing to know what can and should be improved, and not ignore them.
The value of the feedback cap is a peculiar implementation and that is a well-documented departure between the original Threshold design and the PA-7. The upgrading of the rectifier with a modern, faster, softer switching unit is perfectly safe and recommended. The replacement of dried out electrolytics with film caps where possible is also a well-regarded, safe and prudent practice.
My 2 cents about the PA-7 is that it is a beautiful amplifier to look at, and to me, it was worth the time and effort to make it sing again, perhaps even better by correcting some of the flaws I came across, and replacing outdated component with modern, more reliable ones. The original trimpots in the PA-7 were crappy 3-cent parts that replaced with a multi-tiurn Bourns helps tremendously in setting DC offset. This amplifier could have been much BETTER engineered and built but it was not.
So please help fellow forum member realize their amp's true potential with your knowledge and recommend specific, workable changes, including part numbers. Just telling others you never met that they "do not know more than the engineers who created these amps" is not helpful to anyone.
I can't recall where I read it, but the Naks were built to a price point, so corners were bound to be cut. For my part, I'm just looking to refresh old (and possibly failure prone) parts, and since this isn't the only place I've heard about the C102/C202 improvement, that is on my radar as well.
Hi ci11,
Do me a favour and calculate the low frequency cut-off point of the original circuit, please.
Look at the existing DC offset of your amp. I don't know if you performed all the modifications or not, so some of these comments may not apply specifically to you. Anyway, DC offset - please?
Stuff that ain't safe at all.
Messing with the protection circuitry is insane, especially with a product that never had a problem to begin with. No PA-5 amplifier ever had an overzealous protection circuit. People are encouraged to make the protection circuit next to inoperative, that's a problem. Very few PA-7 users had problems with the protection circuit. You know, the 15 ampere industrial circuit breaker always tripped testing the PA7 amplifier into 2 ohms - before protection limited the output. If anything, these amplifiers are capable of too much current, and we have folks who never run these amps to the limits that the service techs have deciding that a problem exists and how to correct it. That's arrogant if you ask me.
The plain fact is this. Others reading these comments are mostly not qualified to make a judgement as to what is and isn't safe. It would really help too if you guys took the time to actually find out where low frequency cut-offs and limiting current was before pushing the keys. Do me a favor an do not repeat things you are not certain of, and have the equipment and experience to back up your claims.
Guess what? I do have the equipment and experience.
So, you want to improve your PA 5 or PA7? Great, use your head and change things that actually matter. Now, as for shoddy construction. Not true. The only amps that were damaged were struck by "technician", or one that destroyed a copper box staple. Never did I have circuit board damage unless the unit was worked on by someone who had no business working on these.
Nakamichi did do a lot more than take Nelson's design and make it pretty. They actually engineered this amplifier based on Nelson's patent and probably with some help from Nelson. That I can't speak to, but I do know the new amp went through a ton of lab tests and listening tests (done in the USA actually) before it ever saw the light of day. If nothing else, the people at Nakamichi do understand how to make great sounding equipment. Look a the low noise electronics in their tape decks if you don't believe that.
Part numbers that you want me to give? Why would I engineer something for everyone to hack away with? I don't do extreme mods, and all you need to know is the number of the parts that are in the amplifier. Doing a proper improvement is not extreme, not rocket science and has more to do with the knowledge of the parts than just increasing capacitance everywhere.
Think of one thing when doing a "mod". If the replacement part you are going to use is larger than the original, it won't fit where the original did. What that means in practical terms is that it could act as an antenna and pick up or transmit signals to places they shouldn't be. You also may be affecting the cooling of nearby parts. Don't forget, some parts are sensitive to temperature. Polystyrene comes to mind. Don't put them in hot places.
That's the basics. It is common sense. If you don't understand the circuit you are messing with, please, don't touch the damn thing. Certainly do not start changing component values without calculating what the changes you are making will affect the circuit.
Look, I get touchy about this. Know why? It's seeing all the destroyed equipment for years and years. People are free to make an informed choice. What is going on here is not informed. It's based on hear-say repeated between people untrained in what they are doing.
Go ahead and change relays, capacitors. Just don't get stupid about it and use your head. Common sense is your friend.
-Chris
Do me a favour and calculate the low frequency cut-off point of the original circuit, please.
Look at the existing DC offset of your amp. I don't know if you performed all the modifications or not, so some of these comments may not apply specifically to you. Anyway, DC offset - please?
Stuff that ain't safe at all.
Messing with the protection circuitry is insane, especially with a product that never had a problem to begin with. No PA-5 amplifier ever had an overzealous protection circuit. People are encouraged to make the protection circuit next to inoperative, that's a problem. Very few PA-7 users had problems with the protection circuit. You know, the 15 ampere industrial circuit breaker always tripped testing the PA7 amplifier into 2 ohms - before protection limited the output. If anything, these amplifiers are capable of too much current, and we have folks who never run these amps to the limits that the service techs have deciding that a problem exists and how to correct it. That's arrogant if you ask me.
The plain fact is this. Others reading these comments are mostly not qualified to make a judgement as to what is and isn't safe. It would really help too if you guys took the time to actually find out where low frequency cut-offs and limiting current was before pushing the keys. Do me a favor an do not repeat things you are not certain of, and have the equipment and experience to back up your claims.
Guess what? I do have the equipment and experience.
So, you want to improve your PA 5 or PA7? Great, use your head and change things that actually matter. Now, as for shoddy construction. Not true. The only amps that were damaged were struck by "technician", or one that destroyed a copper box staple. Never did I have circuit board damage unless the unit was worked on by someone who had no business working on these.
Nakamichi did do a lot more than take Nelson's design and make it pretty. They actually engineered this amplifier based on Nelson's patent and probably with some help from Nelson. That I can't speak to, but I do know the new amp went through a ton of lab tests and listening tests (done in the USA actually) before it ever saw the light of day. If nothing else, the people at Nakamichi do understand how to make great sounding equipment. Look a the low noise electronics in their tape decks if you don't believe that.
Part numbers that you want me to give? Why would I engineer something for everyone to hack away with? I don't do extreme mods, and all you need to know is the number of the parts that are in the amplifier. Doing a proper improvement is not extreme, not rocket science and has more to do with the knowledge of the parts than just increasing capacitance everywhere.
Think of one thing when doing a "mod". If the replacement part you are going to use is larger than the original, it won't fit where the original did. What that means in practical terms is that it could act as an antenna and pick up or transmit signals to places they shouldn't be. You also may be affecting the cooling of nearby parts. Don't forget, some parts are sensitive to temperature. Polystyrene comes to mind. Don't put them in hot places.
That's the basics. It is common sense. If you don't understand the circuit you are messing with, please, don't touch the damn thing. Certainly do not start changing component values without calculating what the changes you are making will affect the circuit.
Look, I get touchy about this. Know why? It's seeing all the destroyed equipment for years and years. People are free to make an informed choice. What is going on here is not informed. It's based on hear-say repeated between people untrained in what they are doing.
Go ahead and change relays, capacitors. Just don't get stupid about it and use your head. Common sense is your friend.
-Chris
Anatech,
I don't know why you keep referring to the "messing with the protection circuit". I never wrote anything about the protection circuit since my amp has it built in into the PCB. There is no daughterboard add-on like many earlier ones. So any reference to the protection circuit is made by someone else, not me.
What I wrote about is my experience with my amp. I made the changes following advice given by Nelson Pass and others in posts where the poster exhibited knowledge of what they were doing. This was in many forums, not just this one.
What started with a simple replacement of old, dried out parts turned into a search and rescue mission of many visible vulnerabilities I simply do not find in better-made equipment.
You are entitled to your opinion but please stop spraying the fire hose at me. If you found something I described or recommended as unsafe, address it to me. Preferably politely. State the facts, may be even question my wisdom or decision, but please - do not assume what I know or not know. I don't do that with you or anyone.
It's your choice if you do not want to be helpful, but I originally came here for help and appreciated all the help I can get, including part numbers that sometimes take months or years to find, especially obsolete ones like the speaker relay. That is not an extreme mod but a very helpful one.
I think you should really get a handle on your obvious anger.
I don't know why you keep referring to the "messing with the protection circuit". I never wrote anything about the protection circuit since my amp has it built in into the PCB. There is no daughterboard add-on like many earlier ones. So any reference to the protection circuit is made by someone else, not me.
What I wrote about is my experience with my amp. I made the changes following advice given by Nelson Pass and others in posts where the poster exhibited knowledge of what they were doing. This was in many forums, not just this one.
What started with a simple replacement of old, dried out parts turned into a search and rescue mission of many visible vulnerabilities I simply do not find in better-made equipment.
You are entitled to your opinion but please stop spraying the fire hose at me. If you found something I described or recommended as unsafe, address it to me. Preferably politely. State the facts, may be even question my wisdom or decision, but please - do not assume what I know or not know. I don't do that with you or anyone.
It's your choice if you do not want to be helpful, but I originally came here for help and appreciated all the help I can get, including part numbers that sometimes take months or years to find, especially obsolete ones like the speaker relay. That is not an extreme mod but a very helpful one.
I think you should really get a handle on your obvious anger.
Hi ci11,
I am trying to be helpful, but the attitude of "let people try for themselves" is a poor one. I have no problem with that advice as long as all the technical issues have been explained as well. That is something I am trying to do. See here:
Anyway, you aren't the target. It's the bad advice and the happy attitude that is distressing. We call it "fat, dumb and happy". This is my area of expertise. Whatever you do for a living is something I would not just "do" following internet advice. I do call the HVAC guy when my heating / cooling system acts up. My car goes to the dealer when I have a problem - even though I can and have rebuilt engines in my youth. At the minimum, I'll ask advice and follow it.
-Chris
I think you missed this in my previous post.
I am trying to be helpful, but the attitude of "let people try for themselves" is a poor one. I have no problem with that advice as long as all the technical issues have been explained as well. That is something I am trying to do. See here:
My advice is simple. Look at the real conditions in the circuit you are contemplating making changes to. Figure out what the changes will do in a real sense and decide if the possible negative aspects outweigh the possible positive claims. Most times you will see that what has been claimed simply isn't true, or that the change is more due to fixing a real problem due to the part being old and defective. Contrary to popular belief these days, the better equipment was not hamstrung so much by cost considerations. Even building the last word in a product will have both cost and reliability considerations applied. That is part of what they call engineering.
I'm not angry. It's more being tired of well intentioned people being given bad advice and passing it on. Everyone has to stop, take a breath and think before applying what they have read on the internet. I'm the guy that some folks think is ripping them off because they got bad news after causing damage to their own property. I was the guy that had to disallow warranty claims for damage done by the customer or their favorite "modification technician" who feels he knows more than the people who do design work as a profession. I hope you can see why watching these nice amplifiers get hacked up would bother me so much. With good equipment, I care. If they are hacking up stuff that doesn't matter, I shut up and roll my eyes normally.
Anyway, you aren't the target. It's the bad advice and the happy attitude that is distressing. We call it "fat, dumb and happy". This is my area of expertise. Whatever you do for a living is something I would not just "do" following internet advice. I do call the HVAC guy when my heating / cooling system acts up. My car goes to the dealer when I have a problem - even though I can and have rebuilt engines in my youth. At the minimum, I'll ask advice and follow it.
-Chris
Anatech,
I did not miss the point of being implied as making suggestions that are unsafe. If you found something I wrote that is factually incorrect or unsafe, you are welcome to challenge it openly. But to suggest that I am advocating tempering with the protection circuit without any evidence is a false accusation, and in very bad form.
You have not seen my amp, you did not have to deal with burned out parts and lifting traces, and voltage rail wire insulation that obviously were underrated for enduring the heat they were exposed to. To call what I saw good engineering is an insult to the profession. What I wrote is about MY experience of restoring and correcting flaws in my PA-7 to a performance and durability level that pleased me and what I consider to be good common sense practice. Along the way, I made changes that are safe, prudent and nice to look at, FOR ME. I shared this experience in the spirit of describing a positive outcome for an effort I decided to take.
I do not do "upgrades" or "service" for others, nor have I accepted offers to do so in the past. I certainly expect that reasonable people would use their own judgment to make the correct decisions for themselves. A few people expressed their appreciation of my experience and I am happy to have been of some help to them.
I did not miss the point of being implied as making suggestions that are unsafe. If you found something I wrote that is factually incorrect or unsafe, you are welcome to challenge it openly. But to suggest that I am advocating tempering with the protection circuit without any evidence is a false accusation, and in very bad form.
You have not seen my amp, you did not have to deal with burned out parts and lifting traces, and voltage rail wire insulation that obviously were underrated for enduring the heat they were exposed to. To call what I saw good engineering is an insult to the profession. What I wrote is about MY experience of restoring and correcting flaws in my PA-7 to a performance and durability level that pleased me and what I consider to be good common sense practice. Along the way, I made changes that are safe, prudent and nice to look at, FOR ME. I shared this experience in the spirit of describing a positive outcome for an effort I decided to take.
I do not do "upgrades" or "service" for others, nor have I accepted offers to do so in the past. I certainly expect that reasonable people would use their own judgment to make the correct decisions for themselves. A few people expressed their appreciation of my experience and I am happy to have been of some help to them.
Hi ci11,
If you describe things that you did to your power amplifier that "are safe for you" to other folks without presenting both sides of an argument, I think you are being irresponsible. To someone else who has little experience, your description of work you performed is seen as a strongly positive endorsement. You become their mentor and you have to act responsibly in that role.
Having seen many PA-7 amplifiers, your description appears to describe an amplifier that was run too hot over a long period of time. Heat kills. You are correct that I haven't seen your amplifier, but I have many others and the average condition does not mirror yours. If you wish to be critical of the design, that is your privilege. But, you are basing your opinion on an amplifier that has seen unusually hot service.
Again, you are not dealing with a group of peers in this case. They need additional information in order to make an informed decision. Expecting anyone who isn't a professional to make these technical decisions isn't even close to being fair. Therefore I can't accept your argument that they can choose for themselves. by accepting the role of mentor, you also must accept the responsibilities that come with it. All I have ever asked is that people do get the additional information they should have, and that you (in this case) present all the information required to make a proper decision. You sidestepped that issue. If you aren't aware of the possible problems that may stem from what you are doing to your own equipment, you should seek the opinions from people who are experienced with this equipment - real trained experience. You can doubt what I am telling you, but understand I am properly trained on that product along with others with decades of experience. I think too, you are unaware of the possible long term effects of what you may have done.
As I type this, I just opened up a Teac CD player, an expensive one. It's been hacked while being "improved". It has problems now, that is why it is on my bench. This is what I have a problem with. The customer paid someone to wreck his CD player and now has to bear the cost of repairing it (if possible). You may not have held the iron, but your directions may be responsible for other equipment with problems. But, that isn't your responsibility, is it? I would say that if anyone follows your example and has problems relating to that, you are at least partially responsible. I do applaud the fact that you will not work on other people's equipment. That is responsible of you.
-Chris
If you describe things that you did to your power amplifier that "are safe for you" to other folks without presenting both sides of an argument, I think you are being irresponsible. To someone else who has little experience, your description of work you performed is seen as a strongly positive endorsement. You become their mentor and you have to act responsibly in that role.
Having seen many PA-7 amplifiers, your description appears to describe an amplifier that was run too hot over a long period of time. Heat kills. You are correct that I haven't seen your amplifier, but I have many others and the average condition does not mirror yours. If you wish to be critical of the design, that is your privilege. But, you are basing your opinion on an amplifier that has seen unusually hot service.
Again, you are not dealing with a group of peers in this case. They need additional information in order to make an informed decision. Expecting anyone who isn't a professional to make these technical decisions isn't even close to being fair. Therefore I can't accept your argument that they can choose for themselves. by accepting the role of mentor, you also must accept the responsibilities that come with it. All I have ever asked is that people do get the additional information they should have, and that you (in this case) present all the information required to make a proper decision. You sidestepped that issue. If you aren't aware of the possible problems that may stem from what you are doing to your own equipment, you should seek the opinions from people who are experienced with this equipment - real trained experience. You can doubt what I am telling you, but understand I am properly trained on that product along with others with decades of experience. I think too, you are unaware of the possible long term effects of what you may have done.
As I type this, I just opened up a Teac CD player, an expensive one. It's been hacked while being "improved". It has problems now, that is why it is on my bench. This is what I have a problem with. The customer paid someone to wreck his CD player and now has to bear the cost of repairing it (if possible). You may not have held the iron, but your directions may be responsible for other equipment with problems. But, that isn't your responsibility, is it? I would say that if anyone follows your example and has problems relating to that, you are at least partially responsible. I do applaud the fact that you will not work on other people's equipment. That is responsible of you.
-Chris
Anatech,
First you accused me of things I did not advocate, then you tell me to take responsibility for others by merely recounting my experience in an open forum.
In 40+ years of dealing with electronics, very seldom have I seen PCB traces lifting to the degree I did with my PA-7. The amp was designed to be biased high and run hot. They knew that from the beginning. So why did they build a fully enclosed case then place the speaker relay and the output coupling cap on the lowest edge of the PCB where there is the highest concentration of heat? Moreover, why were +60V and -60V rail voltage wiring not properly rated and fastened to robust hardware on the PCB? Is that good engineering?
These are flaws. And they were decisions made by Nakamichi. It has nothing to do with the sound or the circuit design but properly engineering a product for sale to paying customers. Good engineering management would have caught these when the PCB is being taped out. They would have been corrected well before it hit manufacturing, and not left to field service to make excuses for.
If you have an aversion to people poking their nose into equipment they own trying to fix them, why are you on a DIY forum? People are not coming to me as a "trained technician" but they do appear to enjoy one person's experience with one amp. I have seen no evidence that anyone has me confused as such nor have I represented myself that way.
I am confident of my means and methods, and am happy with my results. I don't hide and obscure a problem that I see even though I never pretended to an expert - unlike you. So stop venting your anger that is clearly arising from your frustration with others at me and stop accusing me of things I did not do.
First you accused me of things I did not advocate, then you tell me to take responsibility for others by merely recounting my experience in an open forum.
In 40+ years of dealing with electronics, very seldom have I seen PCB traces lifting to the degree I did with my PA-7. The amp was designed to be biased high and run hot. They knew that from the beginning. So why did they build a fully enclosed case then place the speaker relay and the output coupling cap on the lowest edge of the PCB where there is the highest concentration of heat? Moreover, why were +60V and -60V rail voltage wiring not properly rated and fastened to robust hardware on the PCB? Is that good engineering?
These are flaws. And they were decisions made by Nakamichi. It has nothing to do with the sound or the circuit design but properly engineering a product for sale to paying customers. Good engineering management would have caught these when the PCB is being taped out. They would have been corrected well before it hit manufacturing, and not left to field service to make excuses for.
If you have an aversion to people poking their nose into equipment they own trying to fix them, why are you on a DIY forum? People are not coming to me as a "trained technician" but they do appear to enjoy one person's experience with one amp. I have seen no evidence that anyone has me confused as such nor have I represented myself that way.
I am confident of my means and methods, and am happy with my results. I don't hide and obscure a problem that I see even though I never pretended to an expert - unlike you. So stop venting your anger that is clearly arising from your frustration with others at me and stop accusing me of things I did not do.
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ci11,
Breathe, exhale slowly.
I specifically stated that my comments were general in nature until I dealt with specifics. I was clear about that from my first post. If you wish to think otherwise - go ahead.
Recounting your experiences is fine as long as you make it clear when you are doing something normally not recommended. With 40 years in electronics you should be judged more harshly as this infers that you know better. Can we agree on that?
I have to ask, what is your experience? Stereo salesman, proper technician, design engineer? Assembly person maybe? It might help me understand your stance on this. Up to you of course.
I have no problem with people attempting to service their own equipment unless it is beyond them. If you look at my history of posts you will see that. However, I don't like people messing around with better equipment that they should think about protecting their investment on. I think my favorite remark was made by a computer "technician". His view point was that you can't do any harm because "it doesn't work anyway". The height of ignorance. That approach easily takes a minor problem and makes it into irreparable.
As for the folks at Nakamichi, they did not intend for their amplifiers to be biased so hard it did cause PCB damage, or for it not to have sufficient ventilation. You of all people should know that running equipment outside their rated performance conditions will destroy most things no matter how well made. That is one reason why some equipment has a service altitude limit where cooling falls to an insufficient level for reliable operation. Everything has limitations. As for economics, who will pay for equipment that is several thousand dollars more than it is now? That is what making equipment designed to take those conditions would cost. Work out how much a $600 receiver in 1978 would be worth today. See many of those on the market, do you? No, you don't.
I have about the same number of years in the electronics business, many in high reliability fields. I actually work on, specify and install equipment. I even used to sell it in my younger days, but I was always a hands-on technician.
I like people building their electronics. That is mostly why I am here and what I enjoy the most. I will help people work on their own commercial equipment as long as both the person and the equipment are not in danger of damage. At that point I have to speak up, it is what is expected from all technicians and engineers. I get that you don't like the message, but everyone is responsible for their actions, everyone.
-Chris
Breathe, exhale slowly.
I specifically stated that my comments were general in nature until I dealt with specifics. I was clear about that from my first post. If you wish to think otherwise - go ahead.
Recounting your experiences is fine as long as you make it clear when you are doing something normally not recommended. With 40 years in electronics you should be judged more harshly as this infers that you know better. Can we agree on that?
I have to ask, what is your experience? Stereo salesman, proper technician, design engineer? Assembly person maybe? It might help me understand your stance on this. Up to you of course.
I have no problem with people attempting to service their own equipment unless it is beyond them. If you look at my history of posts you will see that. However, I don't like people messing around with better equipment that they should think about protecting their investment on. I think my favorite remark was made by a computer "technician". His view point was that you can't do any harm because "it doesn't work anyway". The height of ignorance. That approach easily takes a minor problem and makes it into irreparable.
As for the folks at Nakamichi, they did not intend for their amplifiers to be biased so hard it did cause PCB damage, or for it not to have sufficient ventilation. You of all people should know that running equipment outside their rated performance conditions will destroy most things no matter how well made. That is one reason why some equipment has a service altitude limit where cooling falls to an insufficient level for reliable operation. Everything has limitations. As for economics, who will pay for equipment that is several thousand dollars more than it is now? That is what making equipment designed to take those conditions would cost. Work out how much a $600 receiver in 1978 would be worth today. See many of those on the market, do you? No, you don't.
I have about the same number of years in the electronics business, many in high reliability fields. I actually work on, specify and install equipment. I even used to sell it in my younger days, but I was always a hands-on technician.
I like people building their electronics. That is mostly why I am here and what I enjoy the most. I will help people work on their own commercial equipment as long as both the person and the equipment are not in danger of damage. At that point I have to speak up, it is what is expected from all technicians and engineers. I get that you don't like the message, but everyone is responsible for their actions, everyone.
-Chris
Anatech,
Why did you pick my Nakamichi story and not the thousands of others much more risky ones on this forum? Why a broad brush attack on righting the wrongs of a company gone by and not acknowledging what they could have, and should have done better?
This is not about me or who I am, but about bringing the beautifully styled PA-7 to a good, safe place where it can excel again. It is the only reason I contributed a story, and that is the flavor in which I shared my findings. I advocated nothing unsafe and all comers should take it for what it is - one owner's story.
And who made you the judge and jury of my experience and who I am?? Do you have a right to scold people at random in online forums? Go "make your day" with someone else. There is no need for me to engage in this useless discourse with you. I find it offensive, not amusing or helpful in the least.
Why did you pick my Nakamichi story and not the thousands of others much more risky ones on this forum? Why a broad brush attack on righting the wrongs of a company gone by and not acknowledging what they could have, and should have done better?
This is not about me or who I am, but about bringing the beautifully styled PA-7 to a good, safe place where it can excel again. It is the only reason I contributed a story, and that is the flavor in which I shared my findings. I advocated nothing unsafe and all comers should take it for what it is - one owner's story.
And who made you the judge and jury of my experience and who I am?? Do you have a right to scold people at random in online forums? Go "make your day" with someone else. There is no need for me to engage in this useless discourse with you. I find it offensive, not amusing or helpful in the least.
ci11
I didn't pick you out, but you are the one who came roaring out of the darkness. I simply haven't seen any other posts like you are referring to. I do have the reputation for making it known when people do unsafe things. So I haven't singled you out, just responded to what you posted. I feel the message is out in this thread now.
I am all about restoring equipment and returning it to a proper working condition. Some of the things that were suggested in this thread were definitely unsafe and unwise to do. Those are the things I will talk about. #1 is increasing filter capacitor size to silly levels. The most stupid example of that was a poor Marantz 500 that had it's meters pulled, face plate filed to allow the rear ends of a couple huge capacitors to poke through. Anyone who know that amp also knows it didn't need any extra capacitance. A wonderful amplifier destroyed for all time by an idiot.
If you have seen the destruction I have, you might be as outspoken as I am.
-Chris
I didn't pick you out, but you are the one who came roaring out of the darkness. I simply haven't seen any other posts like you are referring to. I do have the reputation for making it known when people do unsafe things. So I haven't singled you out, just responded to what you posted. I feel the message is out in this thread now.
I am all about restoring equipment and returning it to a proper working condition. Some of the things that were suggested in this thread were definitely unsafe and unwise to do. Those are the things I will talk about. #1 is increasing filter capacitor size to silly levels. The most stupid example of that was a poor Marantz 500 that had it's meters pulled, face plate filed to allow the rear ends of a couple huge capacitors to poke through. Anyone who know that amp also knows it didn't need any extra capacitance. A wonderful amplifier destroyed for all time by an idiot.
If you have seen the destruction I have, you might be as outspoken as I am.
-Chris
Anatech,
You just admitted to EXACTLY what I said - you singled my comments out but your anger was rooted in something else, a Marantz 500, not a PA-7! What has "roaring out of the darkness" to do with the quality and integrity of my statements? Is this your private old boys club??
The installed cap "upgrade" in my PA-7 is 39,000µF. They fit the 63.5mm clamps that come originally in the amp. The 33,000µF are now smaller at 50.8mm and require different clamps. Each of the 4 39,000µF's.I received actually measured no more than 33,000µF in accordance with their published ±20% spec.
This is what I know as fact and therefore recommended in good conscience to the poster asking the question in post #37. It is not only prudent but also jives with YOUR stated guideline of "no more than 20% higher". I never advocated or agreed with the 47,000µF that the poster asked about. In the same post I also explained that I kept the rectifiers at 15A to avoid potentially higher inrush current casuing overheating issues with the soft start resistors. I gently suggested to him that there is more to it than meets the eye especially when he said he had not studied the schematic. I even told him there were different versions of the schematic so he should make sure his amp matches the schematic he is using.
Is that safe advice? Am I advocating caution? You bet. That is what I wrote to him to be helpful. Because I am safety conscious and polite in asking people to be careful.
Is that what you wrote to him to be helpful? No. Instead, you started ranting and raving at me obviously without reading what I actually wrote, and about something I did not advocate to do. And you have no idea who I am and what I know.
The only explanation I can come up with for your unacceptable behavior is that you want to be the King of the Hill in all matters Nakamichi related because you were once the warranty service tech. I don't want that honor - I only did ONE amp ONE time and have ONE story. Perhaps you saw people coming to me for advice and had to step in to claim your territory by trashing me even when what I recommended is safe and prudent. Perhaps it is to feed your ego. I have no clue.
Well, mister, you picked on the wrong guy. So go back to read my response in post #37 word for word then apologize. I don't know what your problem is but you really need help.
You just admitted to EXACTLY what I said - you singled my comments out but your anger was rooted in something else, a Marantz 500, not a PA-7! What has "roaring out of the darkness" to do with the quality and integrity of my statements? Is this your private old boys club??
The installed cap "upgrade" in my PA-7 is 39,000µF. They fit the 63.5mm clamps that come originally in the amp. The 33,000µF are now smaller at 50.8mm and require different clamps. Each of the 4 39,000µF's.I received actually measured no more than 33,000µF in accordance with their published ±20% spec.
This is what I know as fact and therefore recommended in good conscience to the poster asking the question in post #37. It is not only prudent but also jives with YOUR stated guideline of "no more than 20% higher". I never advocated or agreed with the 47,000µF that the poster asked about. In the same post I also explained that I kept the rectifiers at 15A to avoid potentially higher inrush current casuing overheating issues with the soft start resistors. I gently suggested to him that there is more to it than meets the eye especially when he said he had not studied the schematic. I even told him there were different versions of the schematic so he should make sure his amp matches the schematic he is using.
Is that safe advice? Am I advocating caution? You bet. That is what I wrote to him to be helpful. Because I am safety conscious and polite in asking people to be careful.
Is that what you wrote to him to be helpful? No. Instead, you started ranting and raving at me obviously without reading what I actually wrote, and about something I did not advocate to do. And you have no idea who I am and what I know.
The only explanation I can come up with for your unacceptable behavior is that you want to be the King of the Hill in all matters Nakamichi related because you were once the warranty service tech. I don't want that honor - I only did ONE amp ONE time and have ONE story. Perhaps you saw people coming to me for advice and had to step in to claim your territory by trashing me even when what I recommended is safe and prudent. Perhaps it is to feed your ego. I have no clue.
Well, mister, you picked on the wrong guy. So go back to read my response in post #37 word for word then apologize. I don't know what your problem is but you really need help.
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Wow.
You really do have a persecution complex there.
You edited a lot of what I said out and changed the complexion of the quote.
I gave an example of what I find annoying and possibly ridiculous. I was concerned about what was being recommended to do to these poor Nakamichi amplifiers. I stated in post #1 (#40) addressed to Wildcat from me that....
Look, if you are going to be so touchy, you need to cool off. So far you have refused reasonable requests for information on your amplifier. You don't want to discuss it. I doubt you even checked. No distortion or frequency response readings - nothing. You're the one with an empty bag puffed up to look like it's more.
I already qualified my comments and told you in words that not everything applied to you. That is as far as I am going to go on this. You either accept that or not.
Now, would anyone who has an original amplifier who is contemplating any of these changes measure their DC offset and post it? Let's have a look at this issue / non-issue. You want to improve your amplifier, that's cool. But let's improve them instead of hacking away at imagined problems.
-Chris
You really do have a persecution complex there.
You edited a lot of what I said out and changed the complexion of the quote.
I gave an example of what I find annoying and possibly ridiculous. I was concerned about what was being recommended to do to these poor Nakamichi amplifiers. I stated in post #1 (#40) addressed to Wildcat from me that....
Referring to a group of folks. then with post #43
I already pointed this out to you once in a quote.
So I explained my concerns, clearly I thought.
Again pointing out my stance and intentions.
Look, if you are going to be so touchy, you need to cool off. So far you have refused reasonable requests for information on your amplifier. You don't want to discuss it. I doubt you even checked. No distortion or frequency response readings - nothing. You're the one with an empty bag puffed up to look like it's more.
I already qualified my comments and told you in words that not everything applied to you. That is as far as I am going to go on this. You either accept that or not.
Now, would anyone who has an original amplifier who is contemplating any of these changes measure their DC offset and post it? Let's have a look at this issue / non-issue. You want to improve your amplifier, that's cool. But let's improve them instead of hacking away at imagined problems.
-Chris
Anatech,
You hurled a whole bunch of accusations on this thread implying what I did was unsafe. You claimed to be the authority. You used a Marantz incident as a reflection on a thread discussing Nakamichi.
Then you say I'm touchy and "refused reasonable requests for information on my amp"? What's my amp got to do with anything? And why do you think you can demand anything from me?
My amp is just fine. It was finished over a year ago and performed very well since. It is stable and plays very nicely. It was rebuilt and tuned using suggestions for parts and setting DC offset and bias based on recommendations publicly posted by Nelson Pass'and Jon Soderberg, arguably the 2 foremost experts on Nakamichi and Threshold amps in the world. Anyone can find it, read it and do what they want with it, I did.
If you are issuing a warning to Nakamichi owners all over the world that you are the only one who can sanction how it should be done. I got news for you. And why do I need to "puff up" nay "bag"?? Am I in the service business wanting to make money from others using this thread as customer acquisition? No. Absolutely not. And I said so.
But for you to step into the thread and randomly spray the jungle with bullets disrupting a dialog between 2 other forum members without being relevant is nothing more than an ego trip.You can retain your wonderful kingdom of Nakamichi service, or Marantz service, or whatever you want to do. I want absolutely no part of it.
But your nasty insinuations not only about me but other owners needs to be called out. I don't know how it is where you live, but where I am, people are allowed and encouraged to do what they want. Every person takes responsibility for their own actions.
This is my last interaction with you, and I wish you all the success in your endeavors.
You hurled a whole bunch of accusations on this thread implying what I did was unsafe. You claimed to be the authority. You used a Marantz incident as a reflection on a thread discussing Nakamichi.
Then you say I'm touchy and "refused reasonable requests for information on my amp"? What's my amp got to do with anything? And why do you think you can demand anything from me?
My amp is just fine. It was finished over a year ago and performed very well since. It is stable and plays very nicely. It was rebuilt and tuned using suggestions for parts and setting DC offset and bias based on recommendations publicly posted by Nelson Pass'and Jon Soderberg, arguably the 2 foremost experts on Nakamichi and Threshold amps in the world. Anyone can find it, read it and do what they want with it, I did.
If you are issuing a warning to Nakamichi owners all over the world that you are the only one who can sanction how it should be done. I got news for you. And why do I need to "puff up" nay "bag"?? Am I in the service business wanting to make money from others using this thread as customer acquisition? No. Absolutely not. And I said so.
But for you to step into the thread and randomly spray the jungle with bullets disrupting a dialog between 2 other forum members without being relevant is nothing more than an ego trip.You can retain your wonderful kingdom of Nakamichi service, or Marantz service, or whatever you want to do. I want absolutely no part of it.
But your nasty insinuations not only about me but other owners needs to be called out. I don't know how it is where you live, but where I am, people are allowed and encouraged to do what they want. Every person takes responsibility for their own actions.
This is my last interaction with you, and I wish you all the success in your endeavors.
I took the lid off of my PA-7 today--one of my overload LEDs fell inside when I was cleaning the front panel. Turns out they are just glued on. I tacked them on with a little bit of adhesive, so that's done for now.
I was going to refresh the old cans, but maybe they have been done already. Was Nichicon around when Nak built these amps? There are four black 33000uF Nichicons in their currently. The inside of this amp was really clean. It doesn't look like it has been worked on, but, who knows?
I was going to refresh the old cans, but maybe they have been done already. Was Nichicon around when Nak built these amps? There are four black 33000uF Nichicons in their currently. The inside of this amp was really clean. It doesn't look like it has been worked on, but, who knows?
Hi ci11,
Didn't see your last post.
I am a good technician. It is important to point out errors and wrong information so that others do not follow bad advice. If you do things that aren't recommended, the device may not fail, not until maybe many years down the road. Unfortunately, the folks who actually get stuck with the aftermath are those who come later. Whether that is a technician or new owner of the product, the person who did these things is actually responsible. Kind of like that really slow driver who is driving "safely" who never see the accidents they cause.
It is important to do things properly. Selective reading doesn't excuse a person from the fact that they caused harm, or future harm to the products they work (or hack) on. Even the quality of the lead dress and solder joints is important.
Have fun, but never allow your "modified" equipment to pass to other hands. That would be completely irresponsible.
-Chris
Didn't see your last post.
I am a good technician. It is important to point out errors and wrong information so that others do not follow bad advice. If you do things that aren't recommended, the device may not fail, not until maybe many years down the road. Unfortunately, the folks who actually get stuck with the aftermath are those who come later. Whether that is a technician or new owner of the product, the person who did these things is actually responsible. Kind of like that really slow driver who is driving "safely" who never see the accidents they cause.
It is important to do things properly. Selective reading doesn't excuse a person from the fact that they caused harm, or future harm to the products they work (or hack) on. Even the quality of the lead dress and solder joints is important.
Have fun, but never allow your "modified" equipment to pass to other hands. That would be completely irresponsible.
-Chris
Hi Wildcat,
I am pretty sure they were. Without looking up the manual myself, my quick response would be that they may be the original capacitors.
When an amplifier has been serviced by a good tech, it is very often difficult to tell anyone was working on it. However, the failure rates for these amplifiers has been extremely low. They are now having problems simply due to age. The filter capacitors are rarely bad in these, but an easy way to check them is to fire it up and let it reach operating temperature. Play some music while it's warming up - may as well enjoy the process. Use an oscilloscope on the AC coupling setting for that channel, set for 50 volts per division. Make certain the probe is in the X10 position. Really good cables are simply 10:1 probes. Connect the probe to the capacitor terminal with the voltage on it, and the ground clip should connect to the common "ground". Once connected, reduce the volts per division switch until you have a sort of saw tooth on the screen. As a capacitor fails, it will develop "pips" on the leading edge. The higher the pips are, the worse shape the capacitor is in. If you run music, you will see some of that waveform on your display even with good capacitors. Just watch for that leading edge pip. Check both polarities.
If you can't get to the capacitor terminals, you can probe the bridge rectifier, or the collector tab of an output. Take care not to slip with the probe as the energy can burn the tip right off. Makes an impressive snap too. You might cut your hand badly by jerking back and out with it. Take care when doing anything like this, it can be dangerous.
USB scopes. Make certain that you are using a quality scope. The less expensive ones can only accept 5 VDC, or 5 volts peak any combination of DC and AC wave forms. With a 10:1 probe, that means that your maximum voltage is only 50 volts peak! It's extremely easy to hook onto a larger wave form and blow the scope up. For comparison, a normal oscilloscope normally has a maximum input voltage of 50 volts, 500 volts using a good 10:1 probe. But read the front panel of the scope. My Agilent can accept 300 VAC rms (continuous sine wave), my Tektronix is rated for 400 volts peak. These are both very expensive oscilloscopes. Less expensive scopes tend to have lower breakdown voltages. Some older scopes have much higher limits - read the front panel, or manual. Where ever that information is.
Sound cards are usually limited to 5 V peak as well. Read your information before connecting anything to the inputs of your sound card. Some of these are also very expensive, and a goof here would really hurt.
If you don't have the equipment, have a friend that does give you a hand. Failing that, and honest technician will tell you honestly what the amplifier needs and doesn't need. I would recommend a shop or tech that was authorized warranty for Nakamichi, or a number of other good brands. Revox, McIntosh or Carver should be safe places. There are other good brands that also qualify for being responsible. TV shops are usually a bad choice, and I apologize to the good guys out there in TV service shops. Too many bad apples in that racket. Car audio service people are not tuned into higher end home audio, same can be said of professional and DJ amp repair people. On average, that doesn't mean everyone in those places.
Hopefully you can do this yourself. Read my tag line also.
-Chris
I am pretty sure they were. Without looking up the manual myself, my quick response would be that they may be the original capacitors.
When an amplifier has been serviced by a good tech, it is very often difficult to tell anyone was working on it. However, the failure rates for these amplifiers has been extremely low. They are now having problems simply due to age. The filter capacitors are rarely bad in these, but an easy way to check them is to fire it up and let it reach operating temperature. Play some music while it's warming up - may as well enjoy the process. Use an oscilloscope on the AC coupling setting for that channel, set for 50 volts per division. Make certain the probe is in the X10 position. Really good cables are simply 10:1 probes. Connect the probe to the capacitor terminal with the voltage on it, and the ground clip should connect to the common "ground". Once connected, reduce the volts per division switch until you have a sort of saw tooth on the screen. As a capacitor fails, it will develop "pips" on the leading edge. The higher the pips are, the worse shape the capacitor is in. If you run music, you will see some of that waveform on your display even with good capacitors. Just watch for that leading edge pip. Check both polarities.
If you can't get to the capacitor terminals, you can probe the bridge rectifier, or the collector tab of an output. Take care not to slip with the probe as the energy can burn the tip right off. Makes an impressive snap too. You might cut your hand badly by jerking back and out with it. Take care when doing anything like this, it can be dangerous.
USB scopes. Make certain that you are using a quality scope. The less expensive ones can only accept 5 VDC, or 5 volts peak any combination of DC and AC wave forms. With a 10:1 probe, that means that your maximum voltage is only 50 volts peak! It's extremely easy to hook onto a larger wave form and blow the scope up. For comparison, a normal oscilloscope normally has a maximum input voltage of 50 volts, 500 volts using a good 10:1 probe. But read the front panel of the scope. My Agilent can accept 300 VAC rms (continuous sine wave), my Tektronix is rated for 400 volts peak. These are both very expensive oscilloscopes. Less expensive scopes tend to have lower breakdown voltages. Some older scopes have much higher limits - read the front panel, or manual. Where ever that information is.
Sound cards are usually limited to 5 V peak as well. Read your information before connecting anything to the inputs of your sound card. Some of these are also very expensive, and a goof here would really hurt.
If you don't have the equipment, have a friend that does give you a hand. Failing that, and honest technician will tell you honestly what the amplifier needs and doesn't need. I would recommend a shop or tech that was authorized warranty for Nakamichi, or a number of other good brands. Revox, McIntosh or Carver should be safe places. There are other good brands that also qualify for being responsible. TV shops are usually a bad choice, and I apologize to the good guys out there in TV service shops. Too many bad apples in that racket. Car audio service people are not tuned into higher end home audio, same can be said of professional and DJ amp repair people. On average, that doesn't mean everyone in those places.
Hopefully you can do this yourself. Read my tag line also.
-Chris
Hello everyone:
Has anyone had any experience with Cora Repair Service Center located at 131, 18th Street, Québec, Qc, Canada G1L 2C6, or heard anything of their reputation?
I am the original owner of a Nakamichi PA-5A II in absolutely mint condition with the original packing (100% of it), manuals, original receipt, everything. I love this amp.
It's developed a 60-cycle hum, and I'd really like to get that fixed as well as any other work done to compensate for age and wear on something this old.
Any feedback on them or other recommendations are greatly appreciated.
Has anyone had any experience with Cora Repair Service Center located at 131, 18th Street, Québec, Qc, Canada G1L 2C6, or heard anything of their reputation?
I am the original owner of a Nakamichi PA-5A II in absolutely mint condition with the original packing (100% of it), manuals, original receipt, everything. I love this amp.
It's developed a 60-cycle hum, and I'd really like to get that fixed as well as any other work done to compensate for age and wear on something this old.
Any feedback on them or other recommendations are greatly appreciated.