Counterpoint SA12 Failure

HBombToo · October 2003

Last night I spent a few hours diagnosing a right channel noise problem. I am convinced after many cable, tube and speaker swaps and following the noise through the system that the SA12 has faulty component in its right channel.

I don't see any evidence at this point of burns or dielectric leak from any of the caps. I'll check tonight with my meter to see if any of the caps are shorted but I'm thinking it is a diode somewhere in the path that has failed because it is a consistent noise in the channel. I hope its not the MOSFET because I don't think their availability is there.

Any thoughts are more than welcome during this little quest.

HBomb

dorokusai · October 2003

Sorry to hear of your problem. Just remember that beer does not work as solder flux, and you will overcome all obstacles.

HBombToo · October 2003

http://cgi.audiogon.com/cgi-bin/cl.pl?accstwek&1069968064

Thanks for the Link Russman. If you look at the quality of the solder job on those very small boards I would hope your impressed. I have not soldered for a long time but was pretty good at it a few years ago. I hope its like riding a bike because this tube thing is all DIY for me.

HBomb catches on fire in a few days:rolleyes:

Twin at his worst and I won't rest untill the BEER HOLE is FULL!

organ · October 2003

Sorry to hear about that Hbomb. Did the noise change from from one channel to the other when you swapped tubes? Leaky or broken tubes will cause a continuous noise on the channel they're powering.
You also might want to try cleaning the tube sockets before getting the soldering iron out.
Let's hope you find the source of the problem asap.

Maurice

HBombToo · October 2003

Originally posted by organ
Did the noise change from from one channel to the other when you swapped tubes? Leaky or broken tubes will cause a continuous noise on the channel they're powering.
You also might want to try cleaning the tube sockets before getting the soldering iron out.
Let's hope you find the source of the problem asap.

Maurice

No its definetly the right channel of the SA12 and its definetly not a tube. The problem is there is no visible sign of a burned up or leaking cap. It the needle in the Haystack unfortunatly.

HBomb

organ · October 2003

I know that with older equipments there are restoration sites that will help you nail the problem with their step by step procedures to find the source of the problem. I haven't seen one on Counterpoint equipments yet. If I come across one I'll give you the link.

Maurice

gidrah · October 2003

If you find it to be the MOSfet, let me know the model number and I'll keep an eye out. I know RS sells them. Undoubtedly not any of the ones you'll need. That'd be too easy.

Tour2ma · October 2003

Henry,
I have a link from a search back when an SA 12 on ebay caught my eye. It's somewhere, but damned if I can find it now. The site focussed on SA 12 repair/ upgrade quotes and some chat.

I remember there was a great deal of mosfet discussion, as gidrah mentioned.

I'll keep looking....

Got it...
http://www.altavistaaudio.com/np100.html

HBombToo · October 2003

My board exactly but I did find a difference. In the middle of my board and adjacent to the big caps is a small red cap. Please refer to the attached jpeg and you will see on the lower right between the tubes there is a white oval (I hope). A red capacitor is on my unit but missing on their picture.

am I nuts?

HBomb

BTW... Thanks to both gidrah and Tour:D

after further inspection there is a resistor pair missing on the pic. They are right next to the missing cap? Hmmmmm.....Twin

organ · October 2003

I was just thinking...Could it be a bad/leaky capacitor? Are you getting a hum in that channel?

Is that board you posted a replacement stock board or an upgrade board?

Maurice

HBombToo · October 2003

Originally posted by organ
I was just thinking...Could it be a bad/leaky capacitor? Are you getting a hum in that channel?

Is that board you posted a replacement stock board or an upgrade board?

Maurice

I really hope it is a bad or leaky cap... I began thinking that if it was the MOSFET it just would not work at all(I hope). The board I posted is the exact board that is in my SA12 less the few components I listed. The basic rebuild is a grand and they remove the MOSFET which I don't want to do. I figure I have this old relic and I want it as original as possible. I called Alto Vista and left a message this morning and inquired if I could purchase a schematic through them. I hope they say yes because that would make life so much easier! I'll just shotgun it and replace every cap on the board.

I'll let ya know. today if they call back.

HBomb

HBombToo · October 2003

I just got off the phone with Alta Vista and they are sending the service manual for $42.00 smackers. Thats about 1/2 the price for for a college text book so I guess I should not **** to much.

HBomb

Tour2ma · October 2003

From what I've read on the Sa 12's circuitry, I'd need the college textbook as well.

Good luck...

HBombToo · October 2003

Originally posted by Tour2ma

Good luck...

just looking at the HUGE transformer and BIG BADASSED GREY CAPs is a humbling site. I need all the luck I can get here!

HBomb

Tour2ma · October 2003

How long have you had this bad boy, Henry?

From all I have read it's a wonderful example of a hybrid... warmth and power in one. But have also read that they are a tad on the tempermental side.

HBombToo · October 2003

Originally posted by Tour2ma
How long have you had this bad boy, Henry?

From all I have read it's a wonderful example of a hybrid... warmth and power in one. But have also read that they are a tad on the tempermental side.

Just a couple weeks ago when I moved to KC and found it along with the Modulus phono preamp. The modulus works great but your right about the Counterpoint so far in my experience. I hope it does not turn into a money pit. I'm running my RTA8T's and even with the noise in the right channel the setup images beautifully. When I get rid of the noise I'll be able to tell ya how it really sounds.

Big project ahead of me.
HBomb

HBombToo · October 2003

F1 and I were on an IM session when the mother in-law(which is a mosnomer"cjeck splng:D " called in and bounced the connection.

However, I did receive the pics, "Thankyou", of the carver and am not impressed. IMHO!, good thing you talked to Mr. Grand prior to pulling the trigger. I am not impressed at all when looking at the wiring. Please refer to the attached pic.

My SA12 is very elegant with no pasta!!! and has a huge transformer with 4 massive caps.

Twin

Tour2ma · October 2003

um... Henry? Who you talking to here?

HBombToo · October 2003

Originally posted by Tour2ma
um... Henry? Who you talking to here?

F1... its clear to me:D i hope 1 more beer would not piss any1 off;)

Evil Twin

Counterpoint SA12 Failure

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Counterpoint SA12 Failure

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