Counterpoint SA-220 Capacitor Question

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I just bought a set of replacement tubes for my father's Counterpoint SA-220 which he has had since the early 90's. The tubes have never been replaced so I was really hoping he would realize some sonic improvement.

However, when I removed the top cover, I discovered this:

SA-220c50_zps2jzubmnd.jpg


Remarkably, the amp still works. We have no way of knowing when this may have happened. My father says he has never seen smoke come from the amp. I'm thinking maybe this was a serendipitous discovery as this might have been a precursor to disaster. I know by reading on this forum that if you blow an output channel on this amp, it is pretty much game over.

The capacitor is labeled as C50. C51 is right next to it. I don't know the value yet. I know it needs to be replaced, but I have some questions.

1. Should I replace both C50 and C51?
2. Can anyone recommend good replacement caps?
3. Is it a simple matter of simply replacing the caps or are there any other special considerations I need to make? Are there other components that should be replaced as well?
4. Should I replace ALL the caps in the amp?
5. Once the cap(s) are replaced, will it be ok to simply replace the old tubes?

I am very comfortable replacing components like capacitors etc. but I don't have any real testing background. For example I don't have a scope and a variac etc.

As a side note, it appears that getting access to the bottom of the main board will be quite a chore.

Hopefully someone here can shed some light on this.

Thanks for looking
 
Counterpoint is know for using sub-specs parts.

Amazing. I had better not tell my father this!

This cap seems pretty standard, replace both with the higher voltage that fit in that location.

That's it? As simple as that? That's good news. Is there a brand you can recommend?

Does it seem strange to you that the amp still works? By the way, he isn't using it until this is fixed
 
The kind of failure we see on the picture is usually done by overvoltage. For example into a tube equipment, most of the time the power supply is not regulated. If you start the amp without tube, some supplies may be highers, and the design and parts specs have to take that into account. Counterpoint seems to always have a few parts that are under rated. I repaired a Counterpoint amp where some under specs power resistors had overheated and burn, taking the PCB and some traces/pads with them. Sometime also some caps are too close to a heat source (tube, big wattage resistors) and were not specs 105C but just 85C, and had aged rapidly until death.

The amp I repaired (a SA-12 I think) was really good sounding thought. The guy sold it after a little while but know he regretted. He should had kept it.

Watch when you'll replace the caps for the PCB traces and pads. Counterpoint PCB are easy to damage and are of rather poor quality...

As I said these caps seems to be 'Generic' type. I would use about anything, same value, higher voltage as possible that fit, but don't go overboard. These caps are probably just around 50cents each.

When I said 'the higher voltage that fit' I also meant within reason (that was implicit ;) if they are 16V, used 25 or even 35V for example...

I think that one member here, ANALOG_SA, used to be an authorized repair guy for Counterpoint, well I think he doesn't like the designer that much... I think he said 'Stay away from Counterpoint as far as you can'. I'm guessing he's talking from experience.
 
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Thank you both for your responses.

I think my father would like to keep the amp. I think it is a good match with his SA-5000 preamp.

I opened it up again and found that the caps are Xicon 6800uF 10V 20%. There is no temp rating on them.

Remarkably I happened to have two brand new Nichicon 6800uF 16V 85ºC VR(m) series caps that are the same size . What are the odds of that? I had these from another repair. From what Algar_emi said, it sounds like these will work. Is 85ºC ok?

The real trick here is getting to the bottom of the main board. It looks like a total nightmare just to disassemble this thing. Both of the heatsinks/output boards need to come off each side and I will have to desolder a bunch of leads just to get the board out. What were they thinking? Maybe this is why ANALOG_SA said to avoid Counterpoint.

Since it will be so much work just to remove the board, might it be worth while to replace the bad cap with something "nice"? On another forum I read a recommendation for CU teflon or silver caps in these amps. But maybe that was for the huge caps in the front.

Rayma, are you sure it wouldn't at least be a good idea for starters to also replace the one identical cap (C51) right next to the blown one?

Thanks again for your help!
 
Remarkably I happened to have two brand new Nichicon 6800uF 16V 85ºC VR(m) series caps that are the same size . What are the odds of that? I had these from another repair. From what Algar_emi said, it sounds like these will work. Is 85ºC ok?
Those should be fine. Looks like it's a "general purpose" series, but from a quality Japanese manufacturer at least. 85°C is plenty OK in most places except directly next to a regulator or something.

The cap failing like that may also be an indication of an overvoltage condition, so you'll want to check voltages as well.
The real trick here is getting to the bottom of the main board. It looks like a total nightmare just to disassemble this thing. Both of the heatsinks/output boards need to come off each side and I will have to desolder a bunch of leads just to get the board out.
Joy. And you can't get to it through the bottom of the case? Not service-friendly indeed. And it seems people have found about this before, if this old thread is any indication.
Since it will be so much work just to remove the board, might it be worth while to replace the bad cap with something "nice"? On another forum I read a recommendation for CU teflon or silver caps in these amps. But maybe that was for the huge caps in the front.
Probably not, but rather some small coupling caps.

Anyway, you'd probably be well-advised to hunt for more underrated parts while you're at it.
Rayma, are you sure it wouldn't at least be a good idea for starters to also replace the one identical cap (C51) right next to the blown one?
Might not be such a bad idea indeed if these amps have a history of using underspec'd parts.
 
When I repair stuff, I always try to repair just the problem and not to cause others ;)

In this case since we know these parts are bad, without touching the PCB I would simply cut them apart with a cutter and let the leads exposed, then I would desolder them from the top. Then I would try to reinstall the new ones, again from the top, and if possible solder their pins from the side, leaving the cap standing a few millimeter off the PCB.

These are small caps, and there won,t be any mechanical stress on the leads because the case is light. I do that all the time in my home made double sides PCB without issue.

This way you can replace the caps, and not touch the PCB...

It all depends on the space inside the thing.
 
Again, thanks for the replies

Joy. And you can't get to it through the bottom of the case? Not service-friendly indeed. And it seems people have found about this before, if this old thread is any indication.

Unfortunately, there is not a removable bottom cover. Yes, I read that whole thread while I was researching this problem. I am definitely not alone here!

Algar_emi, that is a great idea! I don't think I would have thought of that. This could make this process MUCH easier. I will have a serious look inside to see if this is possible.

It appears that these two caps are sitting right next to a heat source.

SA-220cap3_zpskx4j9q8o.jpg


I don't know how hot it gets.

Can anyone tell by looking at my pictures what these two capacitors are actually doing? What is their function?

Would it be worthwhile to use a couple of these instead of my VR series?

UKW1C682MHD Nichicon | Mouser

Thanks again
 
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Hi Algar_emi,
Not the way to repair these amps at all!

That capacitor blew due to high ambient temperature coupled with high ripple current. Counterpoint did not use substandard parts at all! What they did was use the parts at too high a level for current and voltage.

In case you are wondering, I was a Canadian warranty service shop for Counterpoint. I still repair them as well.

There are a number of issues with this equipment, servicing them on your own is not advised because of the number of "gotchya's" that exist. If you manage to blow an output, you are in for an expensive repair. Not to mention that the amplifiers are not easy to work on either.

Most of the preamps and power amps have design issues with the power supplies. The best advice I can give is to not get creative. That generally makes things worse then they were. I see enough of these poorly serviced come in. I'd rather they weren't hacked before they arrive. A hacked service attempt is the #1 reason for surprise estimate increases.

-Chris
 
The picture shows a heat-sinked, probably hot component right behind. Go for a replacement with a sufficient voltage handling capability *and* 105°C rating. Newer caps are usually smaller, so it should be possible to find a 16V/25V 105°C cap in approx. the same size as the old one.

Regards,
Rundmaus
 
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Hi Rundmaus,
It actually helps to put in the largest (higher voltage rating) capacitor that will fit at 105°C, or higher if you can find it. Here, the ripple rating is also critical.

Hi BassAmp,
Do yourself a favor and install it from the bottom of the PCB. Don't work from the top unless that really is the only avenue open to you.

-Chris
 
Hi Rundmaus,
It actually helps to put in the largest (higher voltage rating) capacitor that will fit at 105°C, or higher if you can find it. Here, the ripple rating is also critical.

Hi BassAmp,
Do yourself a favor and install it from the bottom of the PCB. Don't work from the top unless that really is the only avenue open to you.

-Chris

Thanks for your input,

I don't really have much of a choice about doing this myself since most places don't even want to touch it, due to the mosfet situation. But this really isn't a problem as I don't think anyone will be as careful as I will be.

While it's tempting to try to replace the caps from the top, I really want to do a nice job so I will go at it from the bottom. I just wish the bottom of the main board was more accessible.

The existing caps are 10V. I can get either 16V or 25V replacements. Just to clarify, you would recommend 25V? Also, if I understand correctly, the higher the ripple current rating the better, right?

Thanks again
 
Mission Accomplished

I finally tackled the job this afternoon and am very happy to report that the amp is working again. I replaced both caps, C50 and C51 with Nichicon KA series for what it's worth. Hey, they say "Audio" on them so they must be good :p

The whole job took just over 3 hours. If there had been a removable cover on the bottom, I'd say it would have taken 30 minutes tops. Oh well.

It seems that there is more low end now. Is it my imagination or could this cap repair be responsible for this?

Tomorrow I am going to retube the amp which is what I was trying to do when I discovered the blown cap in the first place.

Anyway, I just wanted to report back that the job was a success and thanks to everyone who helped me with this.
 
Replace the Sovtek 6922 with ElectroHarmonix 6922.
Replace the EZ81 with a ElectroHarmonix 6CA4/EZ81

Note: EZ81 is the European code for the North American 6CA4.

You may find a closer source in the UK or you could try the the ElectroHarmonix webshop Home | Electro-Harmonix

If you are replacing the 6922s then please replace all four in the amplifier. The EZ81/6CA4 lasts about 2-3 times as long as the 6922, if that is any help. But they (EZ81) are pretty cheap so I used to replace the all five valves at once
 
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