Hi steeno,
Why does that bother you? I see some real beaut's of posts in tube and many other forums.
I have to admit that some people learn with less baggage than others do, and the popular press is not helping at all. But it's still about people learning the facts.
-Chris
Why does that bother you? I see some real beaut's of posts in tube and many other forums.
I have to admit that some people learn with less baggage than others do, and the popular press is not helping at all. But it's still about people learning the facts.
-Chris
Hi Paco,
So even if the part went into service with no defects, they can be caused. That's why I don't debate this or worry about it. I just confirm matching one way or the other. The other is to remove the part from the circuit and measure it.
Do not assume anything!
-Chris
That's an assumption easily made. Some people should try measuring them. It's also possible to change the parameters of one of the pair if they ever go into reverse E-B breakdown. Like when an amplifier goes DC on the output due to a fault. The part that gets reverse biased may have it's gain changed and also become noisy at some point.
So even if the part went into service with no defects, they can be caused. That's why I don't debate this or worry about it. I just confirm matching one way or the other. The other is to remove the part from the circuit and measure it.
Do not assume anything!
-Chris
Ok. Thanks Chris. But I must bring this up again. I've been doing a lot of searching and reading on matching transistors, and still don't know what exactly I would be trying to match between each one...
I've found many many different circuits used to match transistors, but don't know which to go with. Heck, I don't even know what replacement to look for. Chris, you gave me a link to replacement driver transistors, but I guess those won't work in replacing the diff pair right?
Now that I know what the problem is, I feel like I'm back to square one on how to fix it!!!
I've found many many different circuits used to match transistors, but don't know which to go with. Heck, I don't even know what replacement to look for. Chris, you gave me a link to replacement driver transistors, but I guess those won't work in replacing the diff pair right?
Now that I know what the problem is, I feel like I'm back to square one on how to fix it!!!
Wait scratch that. I'll go with the 2N5087 that you recommended earlier. I just don't know how to go about matching them...
Hi Paco,
You can do your preliminary matching by measuring the beta. Try to keep the transistors at room temperature by handling them with pliers or something. Once you have listed the gains with the transistors sitting by it's number, pick out the closest ones and put them in that jig I posted.
The E-B voltage is a non-issue, ignore it. Your transistors will be from the same batch, so E-B voltages will be close anyway. You want to match the beta, that is what will compare and amplifier the current difference between the two bases in a differential pair. Even if E-B voltages are different, that will be a couple mV at the most. A non-issue.
When you use my jig, keep the two transistors close or touching. Allow time for the temperatures between them to equalize before checking the match. If they are way out, you will see that right away.
-Chris
Yup, it turns out that HK used those in later models.
You can do your preliminary matching by measuring the beta. Try to keep the transistors at room temperature by handling them with pliers or something. Once you have listed the gains with the transistors sitting by it's number, pick out the closest ones and put them in that jig I posted.
The E-B voltage is a non-issue, ignore it. Your transistors will be from the same batch, so E-B voltages will be close anyway. You want to match the beta, that is what will compare and amplifier the current difference between the two bases in a differential pair. Even if E-B voltages are different, that will be a couple mV at the most. A non-issue.
When you use my jig, keep the two transistors close or touching. Allow time for the temperatures between them to equalize before checking the match. If they are way out, you will see that right away.
-Chris
Use the PNP matcher right? Either way, with the jig the "O"s are all ground right? I'm just a little confused on what each label means, if you don't mind me asking.
Hi Paco,
The "o"s represent test points for your meter, sockets for the transistors shorting connector positions and power supply connections. The test points are labeled :
TP1 (a or b) [collector or drain of your transistor]
TP2 (a or b) [base or gate of your transistor]
TP3 common [emitter or source of your transistor]
There are diagrams of the two types of transistors to the right of the socket positions.
The power supply connections are labeled either V+, V- or Common. There is a voltage range listed, but I normally use 10 VDC.
The tail current select section at the bottom has an arrow to it and "Short connector". There is a position chart that also lists the current I measured on my unit. Yours should be similar. Now, before you ask, most diff. pairs run at 2 mA, or the 620 ohm position.
Don't forget to use precision resistors for the 100 ohm and 10,000 ohm resistors. The 1K6 resistor is not critical, neither are the current set resistors. 1/4 watt should be fine for most of these, but the 100 ohm parts should be rated at 1 watt really. The 1K6 resistor might be 1/2 watt. Common parts.
This is easy. Read back to my other descriptions as well.
-Chris
Nope.
The "o"s represent test points for your meter, sockets for the transistors shorting connector positions and power supply connections. The test points are labeled :
TP1 (a or b) [collector or drain of your transistor]
TP2 (a or b) [base or gate of your transistor]
TP3 common [emitter or source of your transistor]
There are diagrams of the two types of transistors to the right of the socket positions.
The power supply connections are labeled either V+, V- or Common. There is a voltage range listed, but I normally use 10 VDC.
The tail current select section at the bottom has an arrow to it and "Short connector". There is a position chart that also lists the current I measured on my unit. Yours should be similar. Now, before you ask, most diff. pairs run at 2 mA, or the 620 ohm position.
Don't forget to use precision resistors for the 100 ohm and 10,000 ohm resistors. The 1K6 resistor is not critical, neither are the current set resistors. 1/4 watt should be fine for most of these, but the 100 ohm parts should be rated at 1 watt really. The 1K6 resistor might be 1/2 watt. Common parts.
This is easy. Read back to my other descriptions as well.
-Chris
Ohh. This is all starting to make sense...thank you thank you thank you for this! Heck, most of these parts I could pick up from the local electronics store and have that thing built tomorrow. Not sure where to find the transistor though, but I haven't checked any of the stores yet, so will have to do that...
Hi Paco,
The transistor is not critical either. You want high-ish beta and some dissipation ability. You can always try something and change it later if you want.
-Chris
The transistor is not critical either. You want high-ish beta and some dissipation ability. You can always try something and change it later if you want.
-Chris
Hmmm ok. You mentioned earlier not to use NTE, but the local Fry's only sells NTE transistors so yeah...just thought I'd mention that.
drop in PCB ?
I dont want to threadjack, but does someone make a drop-in
PCB based on the PASS Mosfet design ? I would like to use original case/heatsinks/transformers.
jagtek
I dont want to threadjack, but does someone make a drop-in
PCB based on the PASS Mosfet design ? I would like to use original case/heatsinks/transformers.
jagtek
Hi Paco,
Hi jagtek,
Why not have a look in the Nelson Pass forum? You might find something there.
-Chris
Then shop elsewhere. You need to buy parts that you actually know the characteristics on - for real.
Hi jagtek,
Why not have a look in the Nelson Pass forum? You might find something there.
-Chris
Chris,
I was just talking about that for the transistor in your transistor tester, the 2SA1358. In reality, there are not many local stores that sell parts like that at all anymore. Everything has to be ordered online. I guess I might as well order that transistor as well as 15 or so of the 2N5087s while I'm at it. Is there a recommended brand? I'll likely get them from Digikey, however the brands they sell there for the 2N5087s are ON Electronics or Fairchild Optoelectronics Group. Are either of these worth using?
I was just talking about that for the transistor in your transistor tester, the 2SA1358. In reality, there are not many local stores that sell parts like that at all anymore. Everything has to be ordered online. I guess I might as well order that transistor as well as 15 or so of the 2N5087s while I'm at it. Is there a recommended brand? I'll likely get them from Digikey, however the brands they sell there for the 2N5087s are ON Electronics or Fairchild Optoelectronics Group. Are either of these worth using?
Hi jagtek,
Thank you.
Did you find anything in Nelson's threads?
Hi Paco,
While an NTE may work fine, it will be far more expensive than the real components.
I think you have a good idea. Buy a bunch of 2N5087. On semi is my default manufacturer, but Fairchild should be fine. The bonus is that they also stock the Japanese numbers (KSA, KSB, KSC and KSD. The "K" I think is for Korean. While you're at it, get the transistor sockets and precision resistors. You can buy the double row headers there and use the jumpers taken from old computer cards or mother boards.
Your 2N5087 are priced at $2.14 for 25 pcs. and $6.18 for 100 pcs. They are very inexpensive. Buy the compliment for these while you are there. These are popular transistors. Also consider picking up some MPSA06 and MPSA56, or MPSW06 and MPSW56 (higher dissipation). These signal transistors are cheap and you may as well pick up some that you will use in the future. Buy 25 pcs. of the 2N5087 at the very least.
-Chris
Thank you.
Did you find anything in Nelson's threads?
Hi Paco,
While an NTE may work fine, it will be far more expensive than the real components.
I think you have a good idea. Buy a bunch of 2N5087. On semi is my default manufacturer, but Fairchild should be fine. The bonus is that they also stock the Japanese numbers (KSA, KSB, KSC and KSD. The "K" I think is for Korean. While you're at it, get the transistor sockets and precision resistors. You can buy the double row headers there and use the jumpers taken from old computer cards or mother boards.
Your 2N5087 are priced at $2.14 for 25 pcs. and $6.18 for 100 pcs. They are very inexpensive. Buy the compliment for these while you are there. These are popular transistors. Also consider picking up some MPSA06 and MPSA56, or MPSW06 and MPSW56 (higher dissipation). These signal transistors are cheap and you may as well pick up some that you will use in the future. Buy 25 pcs. of the 2N5087 at the very least.
-Chris
Will be ordering the parts hopefully tomorrow. I am getting really itchy to get this thing working!!!😱
Glad your getting some positive feedback and stuck with it Paco, I would have probably lost it by now with some of the pedantic replys you have had!
Anatech, there are good and bad repair guys, You might be the best? Ive had bad experiences where things have had to be returned three or more times, or found to be repaired with 20 year old 10% carbon resistors salvaged out of an old tv set, What you need is a little more compassion for your fellow enthusiast, Dont be so arrogant, Like said, I got fed up with it, And decided to have a go myself, Ive made many mistakes, But ive learnt from them, Now although never in your league 🙄 I feel I am at a reasonable level where I'm building my own circuits whether PCB or P2P! With most said experts your greeted with the all too familliar head scratching and sharp intake of breath because without the mystique you guys would be out of business, Tell me how many o/p transitors and feedback resistors you have replaced in your career lifetime? dressed up to the customer as if you have worked a miracle?
I'm glad you and your able sidekick have finally relented and offered Paco the help he needs, We all have to start somewhere, who knows Paco might be the next Carlos with all the enthusiasm and passion which is the reason we are here!
Good luck with it Paco!🙂
Anatech, there are good and bad repair guys, You might be the best? Ive had bad experiences where things have had to be returned three or more times, or found to be repaired with 20 year old 10% carbon resistors salvaged out of an old tv set, What you need is a little more compassion for your fellow enthusiast, Dont be so arrogant, Like said, I got fed up with it, And decided to have a go myself, Ive made many mistakes, But ive learnt from them, Now although never in your league 🙄 I feel I am at a reasonable level where I'm building my own circuits whether PCB or P2P! With most said experts your greeted with the all too familliar head scratching and sharp intake of breath because without the mystique you guys would be out of business, Tell me how many o/p transitors and feedback resistors you have replaced in your career lifetime? dressed up to the customer as if you have worked a miracle?
I'm glad you and your able sidekick have finally relented and offered Paco the help he needs, We all have to start somewhere, who knows Paco might be the next Carlos with all the enthusiasm and passion which is the reason we are here!
Good luck with it Paco!🙂
Hi Rocco,
Sorry I appear that way to you.
I have been asked to repair so many destroyed units over the years from people trying to repair their own equipment because someone else said it was easy that I'm tired of it. Without any training and proper equipment, you have little chance of making a proper repair. This is the kind of work I have had to fix. Friends taking electronics and full engineers make the biggest mess out of things.
Over many years, I have had to fire many guys who simply couldn't understand how to fix things, after instruction! Many fired guys had no pride in their work, and it showed. My take on this is pretty simple. A customer pays good money to have you fix something. They should get new parts and a proper, neat job. The unit should perform to spec and be as reliable as a new unit - whatever that unit is. I was trained by an Austrian who did excellent work, and had to pay my dues. I can't see anything wrong with that model.
Now, if you make the decision to work on your own unit, with no training and poor equipment, why should anyone waste their time with you? The outcome is not looking good for one, and you can't give proper information because you don't have the knowledge to be able to determine what looks good, and what doesn't. Nor are you able to properly test things. Sounds like a strong start to a successful repair to me.
There is no mystique here. There is only science and knowledge mixed with common sense. I don't try to fix my furnace, or fridge (both recently), I call in the guy who knows exactly how they work, and I pay them. I don't tell my mechanic how to fix my car, I tell him what's wrong and ask for an estimate, then he fixes it. I have rebuilt 8 cyl car engines when I was younger, but I am not qualified to fix the new ones. In short, I understand what my limits are, and I also understand that it's the details that will get you.
Your main problem is that you don't really understand what you are doing, but it all seems so simple to you. Ignorance is bliss.
In fact, any of my customers will tell you that my answer is this: "I only followed the manual". That's all. Do the job right and do it clean. Also, if you have blown outputs, the bias and drivers need replacing too unless it's a CFP. Then you need to at least test those parts. But then you know that, having learned enough on your own.
I'm sorry if you feel we should help everyone no matter what. That is not realistic to expect. Some people only needed to talk to another tech and they figure it out, others need some more detailed information and still others might be able to get by. They all have some test equipment and tools. Then we have people who finish college or university. Those people think they know everything, but they are really just ready to start learning. Lastly we have people how have decided the work is easy without studying at all. That would be you. If you don't know anything, you haven't a clue how much you don't know. Yet, you feel that people who spent years in school and years in the industry owe you that knowledge for free? No. You need a certain amount of basic knowledge and at least some equipment to be able to talk through a procedure. Without that minimal investment, you are a danger to yourself and others.
I don't feel badly about any decisions I've made here, or while running my service center. Training people is one thing I am well acquainted with. Consider also that every member here that helps another does so at no charge, just their desire to help.
-Chris
Sorry I appear that way to you.
I have been asked to repair so many destroyed units over the years from people trying to repair their own equipment because someone else said it was easy that I'm tired of it. Without any training and proper equipment, you have little chance of making a proper repair. This is the kind of work I have had to fix. Friends taking electronics and full engineers make the biggest mess out of things.
Over many years, I have had to fire many guys who simply couldn't understand how to fix things, after instruction! Many fired guys had no pride in their work, and it showed. My take on this is pretty simple. A customer pays good money to have you fix something. They should get new parts and a proper, neat job. The unit should perform to spec and be as reliable as a new unit - whatever that unit is. I was trained by an Austrian who did excellent work, and had to pay my dues. I can't see anything wrong with that model.
Now, if you make the decision to work on your own unit, with no training and poor equipment, why should anyone waste their time with you? The outcome is not looking good for one, and you can't give proper information because you don't have the knowledge to be able to determine what looks good, and what doesn't. Nor are you able to properly test things. Sounds like a strong start to a successful repair to me.
Probably not. I was just taught to be careful and know what I'm doing. Using old parts is not legal here, unless the customer is informed and consents. I doubt old carbon resistors (that should be thrown out) would qualify. There are 159 normal values of 5% resistors and that is considered to be normal stock. Your experience is not uncommon, and is one reason I have a short fuse with people fixing other people's things when they are not trained.
No I don't. What fixing an amplifier is, is dangerous possibly. It's physics and there are right ways and wrong ways to do things. You can be injured if you don't understand what you are doing. At the least, you will soak up a ton of time as people try to explain basic knowledge to you. Stuff you need to know before even considering doing a repair.
Hardly!
There is no mystique here. There is only science and knowledge mixed with common sense. I don't try to fix my furnace, or fridge (both recently), I call in the guy who knows exactly how they work, and I pay them. I don't tell my mechanic how to fix my car, I tell him what's wrong and ask for an estimate, then he fixes it. I have rebuilt 8 cyl car engines when I was younger, but I am not qualified to fix the new ones. In short, I understand what my limits are, and I also understand that it's the details that will get you.
Your main problem is that you don't really understand what you are doing, but it all seems so simple to you. Ignorance is bliss.
It was about mental attitude and acceptance.
Never happened.
In fact, any of my customers will tell you that my answer is this: "I only followed the manual". That's all. Do the job right and do it clean. Also, if you have blown outputs, the bias and drivers need replacing too unless it's a CFP. Then you need to at least test those parts. But then you know that, having learned enough on your own.
I'm sorry if you feel we should help everyone no matter what. That is not realistic to expect. Some people only needed to talk to another tech and they figure it out, others need some more detailed information and still others might be able to get by. They all have some test equipment and tools. Then we have people who finish college or university. Those people think they know everything, but they are really just ready to start learning. Lastly we have people how have decided the work is easy without studying at all. That would be you. If you don't know anything, you haven't a clue how much you don't know. Yet, you feel that people who spent years in school and years in the industry owe you that knowledge for free? No. You need a certain amount of basic knowledge and at least some equipment to be able to talk through a procedure. Without that minimal investment, you are a danger to yourself and others.
I don't feel badly about any decisions I've made here, or while running my service center. Training people is one thing I am well acquainted with. Consider also that every member here that helps another does so at no charge, just their desire to help.
-Chris
Thanks for the words of encouragement rocco! And, just to be fair to Chris (anatech), I was being quite a bit stubborn at the beginning with this. Honestly, my thought process was "How hard can it be?" (thank you Jeremy Clarkson 😀) and here, several weeks later, I am finding out. I have come so close many times over the past two weeks or so to giving up on this, but keep managing to convince myself not to...
Update on the parts. Always am finding something to keep me from getting this done. Haven't ordered the parts yet...really hoping to before next Wednesday.
Update on the parts. Always am finding something to keep me from getting this done. Haven't ordered the parts yet...really hoping to before next Wednesday.
Hi Paco,
Thank you.
My main concern was for both your safety and to prevent an amplifier from being to damaged by a repair attempt. Once you accepted that there are more things to consider, servicing became an option.
Your parts will arrive quickly. It may take more time to match the darn transistors. Not a job I look forward to, but I do match pairs as soon as I receive any parts order. It takes me hours, but then I am looking for the maximum number of pairs out of the order, or "yield". Don't worry if you forget something, just order it / them later. There is always something else you need.
Once you have all these parts, why not try to make some preamplifiers or buffer circuits. There are many projects here. Since you will have pairs of complimentary signal transistors, look up a "diamond buffer". This is something that sounds extremely good and it's easy to build. You can even modify the basic design to generate some small gain, giving you a preamp better than most. Of course, you need to build a power supply up to the task, but that can be built and upgraded later. Doing this stuff is fun, and when you see how good "home made" things can be, the bug will have a strong hold on you. 😉
-Chris
Thank you.
My main concern was for both your safety and to prevent an amplifier from being to damaged by a repair attempt. Once you accepted that there are more things to consider, servicing became an option.
Your parts will arrive quickly. It may take more time to match the darn transistors. Not a job I look forward to, but I do match pairs as soon as I receive any parts order. It takes me hours, but then I am looking for the maximum number of pairs out of the order, or "yield". Don't worry if you forget something, just order it / them later. There is always something else you need.
Once you have all these parts, why not try to make some preamplifiers or buffer circuits. There are many projects here. Since you will have pairs of complimentary signal transistors, look up a "diamond buffer". This is something that sounds extremely good and it's easy to build. You can even modify the basic design to generate some small gain, giving you a preamp better than most. Of course, you need to build a power supply up to the task, but that can be built and upgraded later. Doing this stuff is fun, and when you see how good "home made" things can be, the bug will have a strong hold on you. 😉
-Chris
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