Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Jul Thu 18, 2019 10:19 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 6 posts ] 
Author Message
 Post subject: Counterpoint SA-7 tube preamp need schematic
PostPosted: Oct Thu 11, 2012 11:06 pm 
Member

Joined: Jun Fri 22, 2007 12:54 am
Posts: 902
Location: San Diego
Need a schematic!!!!

This is a preamp with a solid-state power supply and tubes for the signal path. Counterpoint is no longer in business, and we've searched high and low for service information. Evidently someone who used to work for the company has acquired the original manuals and wants a fortune for copies.

The failure the set had was that four 47 volt zener diodes in series were shorted. These were replaced, but, as you might guess, the replacements get scary hot.

Any service information would be invaluable.

Thanks in advance!

Fred
owner
Classic Audio Repair

_________________
www.repairaudio.com


Top
 Profile  
 
 Post subject: Re: Counterpoint SA-7 tube preamp need schematic
PostPosted: Oct Mon 15, 2012 10:36 pm 
Member

Joined: Dec Wed 05, 2007 11:08 pm
Posts: 748
Location: Marietta/Moultrie GA
Fred, any idea if the power supply is similar or different, compared to an SA-5? I know someone who may have an SA-5 schematic. I'm checking with him.

Regards,
Gordon.

_________________
"It's the guys who think that attending meetings is real day's work that are the problem."- HepcatWilly (on AudioKarma)


Top
 Profile  
 
 Post subject: Re: Counterpoint SA-7 tube preamp need schematic
PostPosted: Oct Mon 15, 2012 10:44 pm 
Member

Joined: Dec Wed 05, 2007 11:08 pm
Posts: 748
Location: Marietta/Moultrie GA
In the meantime, I did talk to someone who was of the opinion that the zeners in these Counterpoint preamps are under-rated from the factory, in power dissipation. They recommended doubling the power rating of the zeners, at the minimum...

If that's true, it would not be hard for me to accept. I've seen a lot of "questionable" parts choices in Counterpoint gear. Caps with too low voltage ratings for the turn-on surge voltages, under-rated resistors and diodes in terms of power handling, running MOSFETS without balancing resistors, and such. Stuff that just makes you shake your head...

Regards,
Gordon.

_________________
"It's the guys who think that attending meetings is real day's work that are the problem."- HepcatWilly (on AudioKarma)


Top
 Profile  
 
 Post subject: Re: Counterpoint SA-7 tube preamp need schematic
PostPosted: Oct Tue 16, 2012 1:48 am 
Member

Joined: Jun Fri 22, 2007 12:54 am
Posts: 902
Location: San Diego
Gordon,

I haven't seen an SA-5, so it's hard to comment on the degree of similarity, except that stringing four 47-volt zeners in series for a total of 188v is quite unusual, so if the SA-5 has that same bizarre arrangement, it's probably the same thing. Some likely reasons that they would be clamping a voltage at 188v are: (1) to provide an inflexible supply voltage to a sensitive input stage (and on this machine one input is labeled "riaa"; or (2) because they're using DC-coupling between tube amplifier stages (yikes!).

So, yes, the SA-5 schematic might be close enough.

Thanks!

Fred
owner
Classic Audio Repair

_________________
www.repairaudio.com


Top
 Profile  
 
 Post subject: Re: Counterpoint SA-7 tube preamp need schematic
PostPosted: May Tue 30, 2017 5:24 pm 
New Member

Joined: May Tue 30, 2017 5:08 pm
Posts: 1
I have an SA-7.1 that's been apart for a while. I just started to put it back together and noticed that all but one filter cap are 100µFD. The one that blew is 47µFD. I have 2 copies of the owner's manual (large & smaller format) but neither has a schematic. Does anyone either have a schematic or know what the value for C201 should be?
cheers


Top
 Profile  
 
 Post subject: Re: Counterpoint SA-7 tube preamp need schematic
PostPosted: Dec Mon 17, 2018 9:55 pm 
New Member

Joined: Dec Mon 17, 2018 9:50 pm
Posts: 1
Not sure if you are still looking for an answer but I had one of these leak in a factory-upgraded unit. Replaced the 500v 47 microfarad cap and it works fine. This is for the line stage.


Top
 Profile  
 
Post New Topic Post Reply  [ 6 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: Dirt Bomb and 15 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB