If it were me. and this is just what i would do. I would remove all the devices from the channel that died. and measure them with the PASS test rig as described on passdiy.com very easy to make. I would then try and find matches from the devices Steve has available. heck tell him the date codes and you might even be able to find some the same!
I would replace the few devices you need. making sure to also check the emitter resistors for the devices that failed!
Put the amps back together and enjoy!
Mucking around with changing transistors to something else kills the value of the amps.
But thats MHO
Zc
I would replace the few devices you need. making sure to also check the emitter resistors for the devices that failed!
Put the amps back together and enjoy!
Mucking around with changing transistors to something else kills the value of the amps.
But thats MHO
Zc
Hi ungie,
That looks roughly right at a glance. You have the basic idea all right. VR3 would indeed adjust the bias current.
If it makes you feel any better, I don't have any schematics either.
Hi Steve,
Amazing! Really? How the devil did you end up with these? Service spares normally do not come from one lot, so the beta ranges a bit wider.
I agree they were pretty good devices. They were abused in some amps and I was always amazed the failure rate wasn't higher. How about one pair in an amp rated for 120 wpc. Nikko Alpha II.
Hi Zero Cool,
You can't treat audio products as if they are vintage cars. There is no list of output device date / run code vs. serial number. Servicing these products are required from time to time, the only important thing is that the service was carried out properly.
It's not unusual to see serviced equipment that outperforms "factory" equipment. This only because the service tech follows the proper procedures and generally takes more care in the alignment of the serviced item. This is especially true for tape machines and the older CD players.
-Chris
That looks roughly right at a glance. You have the basic idea all right. VR3 would indeed adjust the bias current.
If it makes you feel any better, I don't have any schematics either.
Jeff Rowland gave me that information, I just passed it on.
Hi Steve,
Amazing! Really? How the devil did you end up with these? Service spares normally do not come from one lot, so the beta ranges a bit wider.
I agree they were pretty good devices. They were abused in some amps and I was always amazed the failure rate wasn't higher. How about one pair in an amp rated for 120 wpc. Nikko Alpha II.
Hi Zero Cool,
I'm afraid I have to strongly disagree with you here. That is a very poor way to make a repair. All of the output devices in the failed channel should be replaced. Matched is better, but this is not required to have the amp function. It might even meet it's published specs without matched devices. The Stasis type output stage is less critical about matching.
I strongly doubt this. His are from a single run, that's why they measure closely.
That is complete myth! I would consider mixed outputs as a job that needs to be redone, and therefore worth less. If I see a proper set of appropriate devices, then I have a lot more confidence in the amp. Possibly even more than one that is all original.
You can't treat audio products as if they are vintage cars. There is no list of output device date / run code vs. serial number. Servicing these products are required from time to time, the only important thing is that the service was carried out properly.
It's not unusual to see serviced equipment that outperforms "factory" equipment. This only because the service tech follows the proper procedures and generally takes more care in the alignment of the serviced item. This is especially true for tape machines and the older CD players.
-Chris
I was buying in lots of 500 pieces for each polarity. This was my preferred device pair for years. I moved on to the newer plastic cases for both quality and ease of assembly. I guess I should mention I was manufacturing at the time. I did repair for several years for a preferred clientele. You know, famous musicians, studios and studio musicians and very high end audio. I'm afraid I'm in forced retirement now. I have tens of thousands of dollars in parts and no way to use them.
Steve
Steve
"Global Semiconductors in Ontario"
They stuck me with some expensive allegedly NOS parts they represented as Motorola.
Thoughts in general:
Tires can be visually examined for tread wear, no such indicator for old transistors.
All the outputs on an amplifier channel are the same age, and have gone through the same temperature cycles.
Do you only replace devices that have failed?
I do, if the amp is almost new. I figure it was an infant fatality, the others are probably OK (and the unit is still under warranty).
If the unit is older, I replace all the outputs in the failed channel. It is more cost effective in the long run.
When you replace only the three or four that are bad (now) on the older unit, the unit comes back in a short period of time (months, or maybe a year).
They stuck me with some expensive allegedly NOS parts they represented as Motorola.
Thoughts in general:
Tires can be visually examined for tread wear, no such indicator for old transistors.
All the outputs on an amplifier channel are the same age, and have gone through the same temperature cycles.
Do you only replace devices that have failed?
I do, if the amp is almost new. I figure it was an infant fatality, the others are probably OK (and the unit is still under warranty).
If the unit is older, I replace all the outputs in the failed channel. It is more cost effective in the long run.
When you replace only the three or four that are bad (now) on the older unit, the unit comes back in a short period of time (months, or maybe a year).
Hi djk,
My feeling when talking to Jeff Rowland was that he didn't want to reveal his methods. All I got from talking to him was a conceptual idea of his design and some bias current settings. He did give me a couple pointers on the amp I was working on. Seems like a really nice guy but holds his cards close to his chest.
Global. Yeah.
I knew the principles pretty well. I even rented Ali an office and store room in my shop for a few years. Jerry (new owner?) always dreamed of having his own replacement semiconductor brand line and they do know someone with a re-marking machine at the very least.
-Chris
My feeling when talking to Jeff Rowland was that he didn't want to reveal his methods. All I got from talking to him was a conceptual idea of his design and some bias current settings. He did give me a couple pointers on the amp I was working on. Seems like a really nice guy but holds his cards close to his chest.
Global. Yeah.
I knew the principles pretty well. I even rented Ali an office and store room in my shop for a few years. Jerry (new owner?) always dreamed of having his own replacement semiconductor brand line and they do know someone with a re-marking machine at the very least.
Sorry to hear you got stuck. Both Jerry and Ali have a broken moral compass.
-Chris
Hi Steve,
You and I are in the same boat, except that I don't have your excellent stock of transistors. My semiconductor supply was close (not Global) and I didn't have that much money to invest in stock. These days I am by appointment with the better clients from my shop days. About the same range of clients you had and I dealt with The Metalworks recording studio. Many musicians too.
My favorite output devices that were available were those ones you have, and the 2SD424 and 2SB554. I went though the latter devices more often as they were more popular and rated at 15A collector. The ones you are using are rated for 10A collector, so they replaced fewer devices. The higher voltage rating was great for high powered amps, but they were much faster parts than the old Motorola parts and often would oscillate.
Sorry to hear you are in forced retirement (so am I). What happened if you don't mind? Ignore my question if you'd rather not say. My issue was caused by a guy running into the back of my stopped minivan at full highway speed. No brake marks, and I have no memory of the accident really. Just bits and pieces.
Wishing you well, Chris
You and I are in the same boat, except that I don't have your excellent stock of transistors. My semiconductor supply was close (not Global) and I didn't have that much money to invest in stock. These days I am by appointment with the better clients from my shop days. About the same range of clients you had and I dealt with The Metalworks recording studio. Many musicians too.
My favorite output devices that were available were those ones you have, and the 2SD424 and 2SB554. I went though the latter devices more often as they were more popular and rated at 15A collector. The ones you are using are rated for 10A collector, so they replaced fewer devices. The higher voltage rating was great for high powered amps, but they were much faster parts than the old Motorola parts and often would oscillate.
Sorry to hear you are in forced retirement (so am I). What happened if you don't mind? Ignore my question if you'd rather not say. My issue was caused by a guy running into the back of my stopped minivan at full highway speed. No brake marks, and I have no memory of the accident really. Just bits and pieces.
Wishing you well, Chris
djk said:
Another reason to exchange all 44 outputs and drivers is the nominal +90V level of the rail.
Mains voltage has gone up worldwide, 120Vac in the US+CAN, +/-5% surge.
The 2SB600's handle 200V, the 90 volt rails are likely fed by old mains level transformers.
Add some surge during slow hours and several output devices may turn into popcorn, merely due to a rail voltage that's too high to handle during fast transients.
Btw: you don't find it awkward that the bias level of the output stage of the faulty channel is down 75% if the driver section is also biased at 220mA ?
jacco vermeulen said:
Yes I do.
But I also might have not been correct in stating that the driver bias was identical.
I did not record the driver bias on the working channel originally and I'm only going on memory.
Before I go messing with the bias setting I will re-check both amplifiers, drivers and outputs.
anatech said:
Thanks Chris.
It's really nice to feel that I am getting somewhere with these and it now looks like everything is working correctly, save for the missing output transistors on one unit.
I can now decide when I will completely restore these monsters and what I am willing to spend to do it.
With this many output devices it's a good pile of cash to purchase enough to weed out any out of range parts.
I have calls and e-mails in to a few local metalwork sources that I used to deal with to see what I would be in for to strip, clean up, and re-anodize all of the chassis parts and heatsinks.
I might just go with making everything a different colour as I'm not too crazy about the original gold finishing!
Hi ungie,
Let us know how you do and who you dealt with. The lettering might be a problem on the face.
If you are doing the cosmetics, the electronic work is only a fraction of that I bet. If you are going to do this, do it right an you will be able to enjoy these amps for years.
Hi Jacco,
Just being silly, but you do raise a valid point here. If the amp ever clips with no load, it is in danger of failing. I wouldn't be looking forward to that prospect at all. Time to venture into the 250 VDC devices.
-Chris
Let us know how you do and who you dealt with. The lettering might be a problem on the face.
If you are doing the cosmetics, the electronic work is only a fraction of that I bet. If you are going to do this, do it right an you will be able to enjoy these amps for years.
Hi Jacco,
I guess they put out more power these days then!
Just being silly, but you do raise a valid point here. If the amp ever clips with no load, it is in danger of failing. I wouldn't be looking forward to that prospect at all. Time to venture into the 250 VDC devices.I was going to wait to see what happened next. Ungie may have been mistaken on his readings.
-Chris
Anatech:
I was using the 10 amp devices in pairs of three for 100W amps. I never had any problems. I did switch to the 15A higher voltage Toshiba's for higher powered amps. For pro amps I used Motorola, now ON Simi, MJE15024,25 in multiples for powers up to 1200W at 8 ohm. Substantially more at lower impedances.
It is not just transistors I have. I still have everything you need to build amps or preamp. I have about 1000 of one transformer. I also have heat sinks and complete circuit boards in 4 Oz copper for amps. I have 4 Oz Cu boards for discrete op-amps also for preamp use. Things were looking up for a while.
My condition was cancer first followed by a degenerative bone disease that damaged my first 7 vertebra and some nerves. After four surgeries to repair some and remove three I now feel like the Six Million Dollar Man. You wouldn't believe the amount of Teflon and titanium I now carry. And of course there were the bone grafts. This has left me a quadriplegic with more bones still dissolving in other places. I would like to blame the chemotherapy but the fact is my condition is genetic. I got it from my mother.
OT enough for now. But this does explain why I have all these parts. Things happened rather suddenly and it has taken me over a year just to get back to my computer. I haven't had a chance to try to get rid of my stock. I hope someone here can use some.
Steve
I was using the 10 amp devices in pairs of three for 100W amps. I never had any problems. I did switch to the 15A higher voltage Toshiba's for higher powered amps. For pro amps I used Motorola, now ON Simi, MJE15024,25 in multiples for powers up to 1200W at 8 ohm. Substantially more at lower impedances.
It is not just transistors I have. I still have everything you need to build amps or preamp. I have about 1000 of one transformer. I also have heat sinks and complete circuit boards in 4 Oz copper for amps. I have 4 Oz Cu boards for discrete op-amps also for preamp use. Things were looking up for a while.
My condition was cancer first followed by a degenerative bone disease that damaged my first 7 vertebra and some nerves. After four surgeries to repair some and remove three I now feel like the Six Million Dollar Man. You wouldn't believe the amount of Teflon and titanium I now carry. And of course there were the bone grafts. This has left me a quadriplegic with more bones still dissolving in other places. I would like to blame the chemotherapy but the fact is my condition is genetic. I got it from my mother.
OT enough for now. But this does explain why I have all these parts. Things happened rather suddenly and it has taken me over a year just to get back to my computer. I haven't had a chance to try to get rid of my stock. I hope someone here can use some.
Steve
Hi Steve,
I am really very sorry to hear of your condition. That's a harsh blow!
Oddly enough, I have found many injured members here. Some dealing with varying levels of impairment. Unfortunately, you seem to be leading the pack of us. Let me wish you freedom from pain and as much mobility as you can get. Please, enjoy being here as long as you can. I'm not as bad, but feel free to PM me if you would like an ear.
Is there anything you are looking for? Are you well enough to build small projects, or do your current interests lie somewhere else?
We are a community of helpful individuals. May you find some of us close to you...
Best regards, Chris
I am really very sorry to hear of your condition. That's a harsh blow!
Oddly enough, I have found many injured members here. Some dealing with varying levels of impairment. Unfortunately, you seem to be leading the pack of us. Let me wish you freedom from pain and as much mobility as you can get. Please, enjoy being here as long as you can. I'm not as bad, but feel free to PM me if you would like an ear.
At a DIY site?? I don't think that is a problem! Personally, I wish I had better finances as I'm sure you have a couple things that I would love. There should be some members who are closer to you who may be able to help you out some.
Is there anything you are looking for? Are you well enough to build small projects, or do your current interests lie somewhere else?
We are a community of helpful individuals. May you find some of us close to you...
Best regards, Chris
anatec:
Well I don't expect to manufacture again but I still have a few designs I would like to build. You know, to show the people that say they can't possibly work. I hear that a lot about my amps. I hope to someday be able to work on small things - I have a preamp I would like to build. Unfortunately my machine shop is of little use to me at this time. I can no longer lift or even turn over an amp. I do have some amps I would love to build to upgrade my personal system. There are also speakers I have designed but that would belong on another thread.
As for members in my area, so far only c2cthomas has contacted me. Unfortunately it seem some of my luck rubbed off on him and he hasn't had time for hobbies lately. We have gotten off topic and I apologies to the others on this thread. I will be happy to carry on by E-mail If you have more questions or just want to talk. I do have a little time on my hands.
Steve
Well I don't expect to manufacture again but I still have a few designs I would like to build. You know, to show the people that say they can't possibly work. I hear that a lot about my amps. I hope to someday be able to work on small things - I have a preamp I would like to build. Unfortunately my machine shop is of little use to me at this time. I can no longer lift or even turn over an amp. I do have some amps I would love to build to upgrade my personal system. There are also speakers I have designed but that would belong on another thread.
As for members in my area, so far only c2cthomas has contacted me. Unfortunately it seem some of my luck rubbed off on him and he hasn't had time for hobbies lately. We have gotten off topic and I apologies to the others on this thread. I will be happy to carry on by E-mail If you have more questions or just want to talk. I do have a little time on my hands.
Steve
anatech said:
Well we can agree to disagree on some things thats ok.
1- What i said was to check and MATCH the new devices to the existing old devices as best as possible! Key part there left out. I agree that all new of the same device would be the best way to go absolutely. but in interest of keeping the amp as original as possible and IF and only IF all new devices cant be located. then i would try and match a couple of new devices as best as possible to the old devices. and only if there was No other choice would i go with a different make/model of transistor. and even then i wouldn't consider it to be the same amp.
2- We can also disagree about the value of "classic" amps. If these were a run of the mill Hafler, Adcom, etc type amp. then It wouldn't phase me in the least to build a new amp into the old chassis. and IMHO thats exactly what a person would be doing by changing output devices.
If you took a classic Mac tube amp and changed the output tubes to something else...It wouldn't be the same amp and its value would drop considerably. I personally feel the exact same way about solid state amps. I wouldn't even consider spending the same money on a "modified" classic solid state amp! there are too many variables to consider. too many for me to even try and list. IF...and thats a big IF....IF the amp was modded by the factory, the designer, a known reputable mod shop....THEN and only then would i maybe consider the value to be the same or higher. Or if the owner is a known and experienced DIY'er who knows what they are doing and truly understands amp design.
For example. a used Krell KSA-250 has a street value of $2500 in good clean working condition. I wouldn't pay half of that knowing someone changed ANYTHING in that amp. it wouldn't be the same amp. Now if Dan D'Agostino(sp) modified it himself, or if the Krell Factory modified it...I wouldn't even consider it to be an issue. or if a skilled DIY'er made a factory authorized repair I would be cautious but may still consider it.
But if someone want in there and just changed a bunch of stuff during the course of the repair for whatever reason...I wouldn't touch the thing unless is was give away cheap. and even then i would rebuild it back to factory spec!
So i strongly disagree on the subject of value.
Having worked with vintage guitars for so long...some of that has become ingrained in me.
Hi Zero Cool,
Let me address some of your points to explain further. It's not a matter of opinion at all for some of these things!
1. If you have an output device failure, this will force excessive energy to be dissipated in the parts of opposite polarity. This includes the driver transistor in most designs. What I am saying is that you now have a bunch of unreliable transistors in that amp. You have no idea how many amps I have had to rebuild (From other shops) where the "technician" had only replaced the parts that actually failed. The cost of the parts is always more than the cost of a PCB and labour.
2. Huh? Reliability issues will always cause a lower resale value in a product. You do a poor repair and the amp is worth less, no matter what the make is. I can see where you are leading here.
I was warranty service for McIntosh, and have serviced many. They are always worth more when they have fresh tubes from any good brand.
Look, improper service always reduces the value of any object. Too bad that in electronics, these things are often hidden. I restore old radios from the 20s,30s,40s and sometimes 50's. I also restore audio equipment from the early mono tube sets to present. They always end up in usable condition, otherwise there isn't any point to restoring them. If the electronics are not repaired, you may as well only do the casework (killing the value if in good shape).
What you are recommending is improper and irresponsible. All equipment, no matter the make, is deserving of a proper and competent repair job. Notice I'm not talking about any hack work here, but what you have suggested is considered hack work. The argument of "value" and what constitutes the reduction of same is somehow skewed I feel. Would I like to buy unserviced, working items? Yes, but I know it needs service. The only reason I like buying stuff that hasn't been serviced is to avoid the damage some techs cause. However, if buying a used Denon CD player, I want one where the clamp arm mod has been done as those parts are NLA.
-Chris
Let me address some of your points to explain further. It's not a matter of opinion at all for some of these things!
1. If you have an output device failure, this will force excessive energy to be dissipated in the parts of opposite polarity. This includes the driver transistor in most designs. What I am saying is that you now have a bunch of unreliable transistors in that amp. You have no idea how many amps I have had to rebuild (From other shops) where the "technician" had only replaced the parts that actually failed. The cost of the parts is always more than the cost of a PCB and labour.
2. Huh? Reliability issues will always cause a lower resale value in a product. You do a poor repair and the amp is worth less, no matter what the make is. I can see where you are leading here.
I was warranty service for McIntosh, and have serviced many. They are always worth more when they have fresh tubes from any good brand.
Okay, but parts age and some require replacement. Is an amp with problems worth more than one that has been properly serviced? That's about opposite of my experience.
Well, now you are agreeing with what I have already said in my previous post to you. BTW, sometimes the factory service is worse than a good shop or DIYer. Good DIYers will also be trained technicians. There is too much to know for most DIY type people and most are thrown off course by what is written by audiophools.
How about a fuse? This is an extreme, but how far will you take this? Another good example would be any tube product. Tubes are normally user replaceable items and are expected to be replaced. This in the same manner as light bulbs, belts and fuses (by technicians usually). Where are you going to draw the line. From what you have said, the only original tube product to you is one that probably doesn't work, or has serious faults.
Well, that is exactly what replacing all the transistors with new, current ones is all about! Do you realize what happens when transistors are discontinued? I can tell you since I've been servicing for over 30 years. We do not label the product "non-repairable". What we do is find another part that works properly with the same or better specs (where possible). Then, we use complimentary pairs (if that is how they are used) and change the lot. Doing warranty service, if we see a mix of old and new parts in the output stage(s), the entire set is on the estimate. The manufacturer will always back us up on this, and have many times.
I'm still trying to figure out if a problematic amp is worth more than a properly working one. I guess all those guitar amps I've repaired over the years should have been thrown out rather than repaired. Too bad, 'cause I love Fender Twins.
A hacked anything is worth less. A properly serviced unit is always worth more than one that needs work. Something that was damaged has always lost it's intrinsic value that it had before the damage.
Look, improper service always reduces the value of any object. Too bad that in electronics, these things are often hidden. I restore old radios from the 20s,30s,40s and sometimes 50's. I also restore audio equipment from the early mono tube sets to present. They always end up in usable condition, otherwise there isn't any point to restoring them. If the electronics are not repaired, you may as well only do the casework (killing the value if in good shape).
What you are recommending is improper and irresponsible. All equipment, no matter the make, is deserving of a proper and competent repair job. Notice I'm not talking about any hack work here, but what you have suggested is considered hack work. The argument of "value" and what constitutes the reduction of same is somehow skewed I feel. Would I like to buy unserviced, working items? Yes, but I know it needs service. The only reason I like buying stuff that hasn't been serviced is to avoid the damage some techs cause. However, if buying a used Denon CD player, I want one where the clamp arm mod has been done as those parts are NLA.
-Chris
When I talked to Jeff Rowland in 1989, a pair of the Model 10T were $11,000.
The MJ21195/96 are currently $3.29 each in small quantity (10 pcs), $2.45 each (100 lot).
The idea of doing anything less than replacing all the devices with new would never cross my mind.
"Maybe you can find one with one side bad and strip all the outputs out of it??"
Sure, a hack would take a 20 year old Crest and take out the very tired outputs and re-use them.
The MJ21195/96 are currently $3.29 each in small quantity (10 pcs), $2.45 each (100 lot).
The idea of doing anything less than replacing all the devices with new would never cross my mind.
"Maybe you can find one with one side bad and strip all the outputs out of it??"
Sure, a hack would take a 20 year old Crest and take out the very tired outputs and re-use them.
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