My AMC CVT 2030 Power Amplifier's output transformer has blown. Can anyone give me the specification for the ouput transformer? Since AMC has stopped production of audio products, I'm unable to find any spare part for my power amp. I have found a local company which is produce transfomer. But the incharge person told me they need to know the specification of the AMC ouput amplifier. So I would like to ask you all who know the AMC output transformer specification so I can make a new output transformer for my power amplifier.
brent from retrodazeaudio is probably the smartest guy around for these amplifiers. i have no affiliation with him. he seems to answer back quickly.
www.retrodazeaudio.com
www.retrodazeaudio.com
hi matthewong,
It's very unusual to find one of those xfrmrs blown! Yours is only about the second one iv'e heard of in over 10 years. They are proprietary and were uniquely wound by AMC in Taiwan. Have you called AMC to ask it you can purchase parts from them? They might be able to part from a used output tranny...
Dave
It's very unusual to find one of those xfrmrs blown! Yours is only about the second one iv'e heard of in over 10 years. They are proprietary and were uniquely wound by AMC in Taiwan. Have you called AMC to ask it you can purchase parts from them? They might be able to part from a used output tranny...
Dave
Hi Matthewong,
I've never seen one blown. I used to do warranty on them in Canada. No surprise they don't sell audio anymore though.
Two things you have. The core size and rated power, plus you know it's running EL34's. Why they soldered them in I'll never know.
Secondly, you have another good one you can measure to get the turns ratio. Send it in to get copied or measured. My vote is measured and buy th eclosest stock unit.
Now, AMC was a value priced product. I would not be surprised that a new output transformer might be a substantial upgrade. While you're at it, pull the tubes out by any means that saves the PC Board. Install sockets and put a good matched pair in. You will need to cut a section out of the "U" bracket that holds the board.
-Chris
I've never seen one blown. I used to do warranty on them in Canada. No surprise they don't sell audio anymore though.
Two things you have. The core size and rated power, plus you know it's running EL34's. Why they soldered them in I'll never know.
Secondly, you have another good one you can measure to get the turns ratio. Send it in to get copied or measured. My vote is measured and buy th eclosest stock unit.
Now, AMC was a value priced product. I would not be surprised that a new output transformer might be a substantial upgrade. While you're at it, pull the tubes out by any means that saves the PC Board. Install sockets and put a good matched pair in. You will need to cut a section out of the "U" bracket that holds the board.
-Chris
I own one of these and have repaired them as well. The irons are top notch and designed by the the engineer of the early NAD line. Their value priced phylosophy was based on the modular design makeing it cheaper to manufacturer. Soldering the tubes was intentionally done as it "sounded" better. It was also before the tube rolling craze. And by soldering the tubes in they were able to attain the european "UL type" certifications Semco, Nemco, Demco etc. This was quite an acheavement for a tube product and was for selling/marketing purposes.
As far as 'copying' the transformers...I dont know. They were made after many weeks of experimentation with a lot of tricks to make them perform and sound better and be reliable. anatech is right. Even IF you were able to replace them the new transformers will undoubtedly sound different. If affordible it might be a good idea to replace them both.
It would also be a good idea for several reasons to replace the soldered tubes with sockets.
The main reasons are for the heat transfer and for general replacement/repair.
This is one of the best sounding sleeper tube amplifiers on the market. There are several tricks you can do to make it sound even better.
Just out of curoiusoty what tubes are in your unit. Some of the earlier units had Siemens tubes in them.
-Dave
As far as 'copying' the transformers...I dont know. They were made after many weeks of experimentation with a lot of tricks to make them perform and sound better and be reliable. anatech is right. Even IF you were able to replace them the new transformers will undoubtedly sound different. If affordible it might be a good idea to replace them both.
It would also be a good idea for several reasons to replace the soldered tubes with sockets.
The main reasons are for the heat transfer and for general replacement/repair.
This is one of the best sounding sleeper tube amplifiers on the market. There are several tricks you can do to make it sound even better.
Just out of curoiusoty what tubes are in your unit. Some of the earlier units had Siemens tubes in them.
-Dave
Today I have found a factory that really making audio transformer, but the price is a bit expensive, but I don't care, I just need to fix my power amp and make it run again. The staff there told me they need all the specification to make a new one, but I'm not dare to give the good one OT to them, if they can't make it, my AMC power amp will gone forever. I have sent email to AMC, but they never reply my email. So does any one know the specification for the OT? I got the service manual and there is a page for OT, but I don't understand the diagram.
Hi Dave,
Did you work at AMC in the States? I may have dealt with you. If so, you were the most helpful person I came in contact with, and for that I thank you.
Long story short. The AMC line was purchased from the factory with zero warranty. The distributor in the country that sold the equipment was responsible for warranty and parts costs. In Canada, parts were generally unavailable because the Canadian distributor did not buy replacement parts until the 11th hour, then not enough.
I have trouble understanding why a tube socket would stand in the way of safety approvals. Other companies did just fine. Possibly this was the least expensive route they could take. That I'll believe. They then shifted the costs to the consumer. They were not happy about this. Also, it takes more than weeks to design an output transformer from scratch. What I believe happened was they took an inexpensive transformer and tweaked it to be acceptable. Nothing wrong with that. I would have great difficulties in believing that those transformers were better than a stock Hammond. Edcor may have a perfect replacement actually.
A transformer can be copied. Once you have the transformer in hand you can measure all electrical characteristics. You can easily do the metallurgy and unwind it so you have all the details. There are companies that do this. I will bet most stock transformers will perform better. They just cost more. This matters for manufacturing, but not nearly so much for the end user buying two.
-Chris
Did you work at AMC in the States? I may have dealt with you. If so, you were the most helpful person I came in contact with, and for that I thank you.
Long story short. The AMC line was purchased from the factory with zero warranty. The distributor in the country that sold the equipment was responsible for warranty and parts costs. In Canada, parts were generally unavailable because the Canadian distributor did not buy replacement parts until the 11th hour, then not enough.
I have trouble understanding why a tube socket would stand in the way of safety approvals. Other companies did just fine. Possibly this was the least expensive route they could take. That I'll believe. They then shifted the costs to the consumer. They were not happy about this. Also, it takes more than weeks to design an output transformer from scratch. What I believe happened was they took an inexpensive transformer and tweaked it to be acceptable. Nothing wrong with that. I would have great difficulties in believing that those transformers were better than a stock Hammond. Edcor may have a perfect replacement actually.
A transformer can be copied. Once you have the transformer in hand you can measure all electrical characteristics. You can easily do the metallurgy and unwind it so you have all the details. There are companies that do this. I will bet most stock transformers will perform better. They just cost more. This matters for manufacturing, but not nearly so much for the end user buying two.
-Chris
Hey Chris,
Yes I did for about 7 years. Thank you for the helpfulness compliment. Tough job in an even tougher business. Were you the repair guy for the Canadian distributor? Even so you were all a bunch of great guys! You are correct about the distribution, though the details should remain between us. To tell you the truth about the sockets i never did understand the concept either??? The marketing dept. never accepted this and pummeled the president for several years until the change was given the green light.
The transformer was made from scratch and like I say took MANY weeks to develope, and you are right about duplicating. Transformers should sound even better in todays' world with all we have learned. I would be VERY interested to find that out! I called the marketing manager at AMC but he was on vacation... I expect he can be coaxed out of a transformer when he comes back in a few days. I don't think it will take too much to get one out to you.
Curious: Have you done any mods to it? What kind have you done?
Cheers
-dave
Yes I did for about 7 years. Thank you for the helpfulness compliment. Tough job in an even tougher business. Were you the repair guy for the Canadian distributor? Even so you were all a bunch of great guys! You are correct about the distribution, though the details should remain between us.
To tell you the truth about the sockets i never did understand the concept either??? The marketing dept. never accepted this and pummeled the president for several years until the change was given the green light. The transformer was made from scratch and like I say took MANY weeks to develope, and you are right about duplicating. Transformers should sound even better in todays' world with all we have learned. I would be VERY interested to find that out! I called the marketing manager at AMC but he was on vacation... I expect he can be coaxed out of a transformer when he comes back in a few days. I don't think it will take too much to get one out to you.
Curious: Have you done any mods to it? What kind have you done?
Cheers
-dave
Hi Dave,
I'm very glad to be able to "talk" to you again. Yes, I did some service for them. As you know, other issues came up.
I never really played with any of these. They were out immediately after they were repaired. Never did get a stock one to play with either. I still have a dead PCB for one of those models (sans tubes). They had Sovteks in them (ones in Canada anyway), there could have been other makes for all I know.
I have worked extensively with some Counterpoints.
-Chris
I'm very glad to be able to "talk" to you again. Yes, I did some service for them. As you know, other issues came up.
I never really played with any of these. They were out immediately after they were repaired. Never did get a stock one to play with either. I still have a dead PCB for one of those models (sans tubes). They had Sovteks in them (ones in Canada anyway), there could have been other makes for all I know.
I have worked extensively with some Counterpoints.
-Chris
Hi Matthewong,
You have checked these windings out of circuit, right?
The primary may have shorted. If that's the case, inspect where the wires enter the coils. Normally there is only one defect and where the wires cross over each other is the most likely place for your short.
Take pictures before you begin disassembling things.
-Chris
You have checked these windings out of circuit, right?
The primary may have shorted. If that's the case, inspect where the wires enter the coils. Normally there is only one defect and where the wires cross over each other is the most likely place for your short.
Take pictures before you begin disassembling things.
-Chris
Matthewong,
did you get a chance to find out which side the transformer was on? Each transformer is a mirror image. The transformers are not the same. Check it out and let me know.
Also can you take a close look and check out the output tube module to see if there are any parts blown.
Best,
Dave
did you get a chance to find out which side the transformer was on? Each transformer is a mirror image. The transformers are not the same. Check it out and let me know.
Also can you take a close look and check out the output tube module to see if there are any parts blown.
Best,
Dave
What's the mystery?
If I remember correctly, this amplifier used push-pull EL34. They wouldn't have been triode-strapped because that would only produce 15W or so, so they were probably used as pentodes, or possibly in ultra-linear. If UL, then they were probably 6ka-a with 43% taps (lowest distortion) or (20% taps (higher power). That's with cathode bias (and Class A), but as the valves were poorly ventilated, they might have been run cooler with fixed bias in Class B, in which case the transformer would be more likely to be 3.5ka-a. The output would have been configured for 8 Ohms. So, look for a big 470 Ohm resistor on pin 8 of each valve; if it's there you have cathode bias. If not, look for a potentiometer or two feeding pin 5 via a largish resistor (470k or so); if that's there, you have fixed bias. Count how many wires come out of each output transformer and see where they go. At the end of all this, it should be quite easy to work out what is needed.
If I remember correctly, this amplifier used push-pull EL34. They wouldn't have been triode-strapped because that would only produce 15W or so, so they were probably used as pentodes, or possibly in ultra-linear. If UL, then they were probably 6ka-a with 43% taps (lowest distortion) or (20% taps (higher power). That's with cathode bias (and Class A), but as the valves were poorly ventilated, they might have been run cooler with fixed bias in Class B, in which case the transformer would be more likely to be 3.5ka-a. The output would have been configured for 8 Ohms. So, look for a big 470 Ohm resistor on pin 8 of each valve; if it's there you have cathode bias. If not, look for a potentiometer or two feeding pin 5 via a largish resistor (470k or so); if that's there, you have fixed bias. Count how many wires come out of each output transformer and see where they go. At the end of all this, it should be quite easy to work out what is needed.
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