Thanks for responding. The local electronics repair guy sent me this picture of it.. That looks like a plate Counterpoint attached to the transformer. If me memory serves me correctly Counterpoint replaced the transformer under warranty many years ago.
Attachments
Probably a stock transformer with their label on it.
The tech is asking YOU to find a sub? That's his job.
The tech is asking YOU to find a sub? That's his job.
The tech said he was looking for a replacement but not getting anywhere. I knew I was taking a chance going to him as he does audio equipment but is by no means a specialist.
It looks like Counterpoint had the transformer made to their spec? I'm probably out of luck. I spent $300 replacing capacitors and other components and brought the piece home and it sounded great. For about an hour. Then there were some bad sounding snaps and no power. I fear the transformer may have been the problem all along.
I'll ask him. But he doesn't give me much confidence. I'm growing less enthusiastic about having the unit repaired.
Some transformer houses can rebuild bad transformers.
Check with someone local so they can take a look at it.
Check with someone local so they can take a look at it.
Do you have any specs on the transformer?? Primary voltage? Secondary voltage?? 1/2/3 kVA?? Dimensions LxWxH. If you can't find exact replacement then I would be looking at major manufacturers offering in International designs. Multi primary configuration along with secondary taps. Lots of adjustability and remember doesn't have to be exactly on just close. Look at Siemans. SOLA. GE etc. Contact Antek about winding custom. Also many smal mom and pops out there too
I was warranty for Counterpoint until their end. Your service guy doesn't sound great.
It was probably running too hot. The transformers were marginal, if the bias was too high that would do it.
Without looking, you basically have the heater winding and power for the solid state stage. Then you have the B+ for the tube stage. so ...
From my service information:
37 - 0 - 37 @ 7 amperes
8 @ 2 amperes
250V @ 30 mA
Output bias is 100 mA per device
A larger transformer core and slightly lower bias would help. I forget who I had making new transformers, great company. Almost any good transformer manufacturer will make a better part. You could use two, one for the tube section and the other for the solid state section (74 VCT @ 7A or better). Much easier to find, or it's a custom job.
About outputs. They were specific mosfets (Harris), other brands won't work right due to a Vgs shelf (gate charge issue). Those mosfets must be extremely tightly matched, and I mean really tight. I don't repair these using the original output stage, a BJT stage is much better and runs a great deal cooler.
It was probably running too hot. The transformers were marginal, if the bias was too high that would do it.
Without looking, you basically have the heater winding and power for the solid state stage. Then you have the B+ for the tube stage. so ...
From my service information:
37 - 0 - 37 @ 7 amperes
8 @ 2 amperes
250V @ 30 mA
Output bias is 100 mA per device
A larger transformer core and slightly lower bias would help. I forget who I had making new transformers, great company. Almost any good transformer manufacturer will make a better part. You could use two, one for the tube section and the other for the solid state section (74 VCT @ 7A or better). Much easier to find, or it's a custom job.
About outputs. They were specific mosfets (Harris), other brands won't work right due to a Vgs shelf (gate charge issue). Those mosfets must be extremely tightly matched, and I mean really tight. I don't repair these using the original output stage, a BJT stage is much better and runs a great deal cooler.
Thank you for the help. I sent the amp down to Vista a couple of times to get warranty work. I was very happy with the way it was handled. I don't think my service guy is up to much more than troubleshooting and soldering replacement items. I'm just wondering if the unit is worth repairing at this point.
Well, it is compared to anything current and new in a hybrid amp.
I nearly have a bunch of enhancements completed to that design using a bipolar output stage and other fixes. Much lower distortion and cleaner sound, still sounds like a Counterpoint (that part was difficult). A couple have been running for 10 years without trouble. There are some improvements I'd like to make. I also redesigned most of the Counterpoint preamps. Lower noise and they don't blow up anymore. Nothing involves stupid capacitors or special resistors or anything else that doesn't fit the PCB.
So is it worthwhile? Depends. Most used replacements are hacked or need a total rebuild. The service you had was mostly unnecessary if you went for an upgrade. Those were totally ineffective. It's too bad they didn't deal with the root issues, it wouldn't have failed again.
What I would do is this. Power the amp up on other power supplies to make sure the rest is working. Even if he sparked up the solid state supply only, you could tell if an output was gone. Do that before investing anything in it. It won't give bias current unless the heater supply is also run, easily done. There is a relay that shorts the bias voltage until it times out. He could pull that relay to test I guess. If you have even one dead output transistor and it needs a power transformer, you have a case and heat sinks. Build a kit and install that. The case is nice and it has good heat sinks.
You aren't in Canada, so I am not trying to go for business at all.
I nearly have a bunch of enhancements completed to that design using a bipolar output stage and other fixes. Much lower distortion and cleaner sound, still sounds like a Counterpoint (that part was difficult). A couple have been running for 10 years without trouble. There are some improvements I'd like to make. I also redesigned most of the Counterpoint preamps. Lower noise and they don't blow up anymore. Nothing involves stupid capacitors or special resistors or anything else that doesn't fit the PCB.
So is it worthwhile? Depends. Most used replacements are hacked or need a total rebuild. The service you had was mostly unnecessary if you went for an upgrade. Those were totally ineffective. It's too bad they didn't deal with the root issues, it wouldn't have failed again.
What I would do is this. Power the amp up on other power supplies to make sure the rest is working. Even if he sparked up the solid state supply only, you could tell if an output was gone. Do that before investing anything in it. It won't give bias current unless the heater supply is also run, easily done. There is a relay that shorts the bias voltage until it times out. He could pull that relay to test I guess. If you have even one dead output transistor and it needs a power transformer, you have a case and heat sinks. Build a kit and install that. The case is nice and it has good heat sinks.
You aren't in Canada, so I am not trying to go for business at all.
anatech
Did you try Exicon ECW20N20 and ECW20P20 as replacement transistors to the Harrisis ???
Would not be too far of from the originals and the cathode follower would be strong enough to drive them properly.
No need for source resistor as per the original designers request.
Two complementary pairs of these might suite well and have a similar configuration of harmonics in the distortion to come close to the original Harris.
A BJT output is a completely different animal so I'm not surprized that you had to struggle a bit to keep the original Counterpoint sound which is very good by the way.
Like it a lot.
Did you try Exicon ECW20N20 and ECW20P20 as replacement transistors to the Harrisis ???
Would not be too far of from the originals and the cathode follower would be strong enough to drive them properly.
No need for source resistor as per the original designers request.
Two complementary pairs of these might suite well and have a similar configuration of harmonics in the distortion to come close to the original Harris.
A BJT output is a completely different animal so I'm not surprized that you had to struggle a bit to keep the original Counterpoint sound which is very good by the way.
Like it a lot.
Hi flex2,
No, the Exicon parts have a different pinout for one. The matching requirements are severe and source resistors were not used in these. Without feedback, source resistors caused a lot of distortion. The factory did not use source resistors and MC was dead set against them, he may have been forced to use them later. You can make the amp go with the Exicon parts, but not well. It will be expensive due to the matching requirements. I made a jig specifically for this.
I experimented with these amps a lot. There are a number of design goofs (worse than mistakes). I came up with a version that was reliable, ran much cooler, had much lower noise and distortion, plus the DC offset became stable without wandering all over as is normal. It required a total redesign keeping the original basics, four new PCBs to replace the original one. I separated the power supply, voltage amp stage and each output section got a PCB. No more mosfets. The folks I made prototypes for strongly preferred the new version and these people LOVE Counterpoint. I have a bunch to do once I finalize the new design.
Basically, if you have a dead output or more, time for an updated amplifier that has far better measured specs and sounds better by all accounts. It is also far more reliable - and repairable on top of that.
No, the Exicon parts have a different pinout for one. The matching requirements are severe and source resistors were not used in these. Without feedback, source resistors caused a lot of distortion. The factory did not use source resistors and MC was dead set against them, he may have been forced to use them later. You can make the amp go with the Exicon parts, but not well. It will be expensive due to the matching requirements. I made a jig specifically for this.
I experimented with these amps a lot. There are a number of design goofs (worse than mistakes). I came up with a version that was reliable, ran much cooler, had much lower noise and distortion, plus the DC offset became stable without wandering all over as is normal. It required a total redesign keeping the original basics, four new PCBs to replace the original one. I separated the power supply, voltage amp stage and each output section got a PCB. No more mosfets. The folks I made prototypes for strongly preferred the new version and these people LOVE Counterpoint. I have a bunch to do once I finalize the new design.
Basically, if you have a dead output or more, time for an updated amplifier that has far better measured specs and sounds better by all accounts. It is also far more reliable - and repairable on top of that.
Great. Keep up the good work you do. I assume a lot of Counterpoint owners are thankful that someone can help keep them alive.
Thanks flex2,
Still finalizing the SA-100/12 design. It will translate to the SA-220 once stable. I have a bunch of those on hold as well. Designing these sucks up a great deal of time when you're working already. I bought some dead ones to work with as the guy with the SA-100's doesn't want to send them back as he is using them all the time. That slowed development.
Still finalizing the SA-100/12 design. It will translate to the SA-220 once stable. I have a bunch of those on hold as well. Designing these sucks up a great deal of time when you're working already. I bought some dead ones to work with as the guy with the SA-100's doesn't want to send them back as he is using them all the time. That slowed development.
If you want help with simulation to reach stabilization in the tube section I can help you out.
I have simulated a lot around Counterpoint SA-12 and SA-220 to learn about what was so special with them and used
that knowledge when designing my own hybrid DIY products.
Send me a private message and I will reply with some pictures of simulations of SA-12 and SA-220 so you can judge if it can help you on your journey.
I have simulated a lot around Counterpoint SA-12 and SA-220 to learn about what was so special with them and used
that knowledge when designing my own hybrid DIY products.
Send me a private message and I will reply with some pictures of simulations of SA-12 and SA-220 so you can judge if it can help you on your journey.