I've got a Counterpoint SA-3000 that was functioning but clearly needed leaking caps and some out of spec plate resistors replaced. In the course of preparing to do that job, I have found that the 3 Zeners in the power supply are so toasted that the surface of the bodies has degraded to the point I can't read any numbers.
I'd rather not pull these to test them out of circuit and risk damage; can anyone please help me with these Zener specs so I can order the correct ones?
Thank you very much,
Greg
I'd rather not pull these to test them out of circuit and risk damage; can anyone please help me with these Zener specs so I can order the correct ones?
Thank you very much,
Greg
Attachments
If the unit powers up just measure the voltage across them, should get you in the ball park.
Craig
Craig
Thank you, Craig. I neglected to clarify that I'd already pulled caps and wiring. I should have measured before I did this.
However, I've decided to have the preamp updated and improved by Chris Bridge - Anatech, who will be replacing these as well as other components.
Cheers,
Greg
However, I've decided to have the preamp updated and improved by Chris Bridge - Anatech, who will be replacing these as well as other components.
Cheers,
Greg
Just set up the Zeners with a resistor and power supply, and determine the Zener voltage(s) empirically.
There may be several values. But you still have to find the power rating by measuring the case size.
There may be several values. But you still have to find the power rating by measuring the case size.
Thank you, Rayma - that was indeed what I had planned to do if no one knew the part numbers offhand.
Schematics for those are hard to get. Here's some stuff.
Counterpoint SA-3000 Service Manual
Counterpoint SA-3000 Dual-Channel Hybrid Preamplifier Manual | HiFi Engine
Counterpoint SA-3000 Service Manual
Counterpoint SA-3000 Dual-Channel Hybrid Preamplifier Manual | HiFi Engine
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If anatech doesn't have the schematics, you could post a wanted ad, offering to pay for a set that someone
has bought previously, and that they no longer need. Just copying them could be a copyright violation.
has bought previously, and that they no longer need. Just copying them could be a copyright violation.
That is a good suggestion that I may act on. Fortunately, Chris is very well equipped to work on these, which is why I'm sending it off to him; I have seen his audio analyzer test results of his work on a previous unit.
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That should be obvious from the package size... 5W
So the part numbers are:
1N5368B
1N5377B
1N5378B
It's odd that they did not use three equal Zener voltages, but now you have enough info to replace them.
Thank you for that information, Alan. I was at least aware they were 5W, based on package and lead size.
Rayma - they are wired in series.
Counterpoint mounted these Zeners beneath a plastic doghouse. The heat was effectively trapped, which cooked the bottom of the board even more than the top for some reason; I suspect the solder joints weren't great and there was added resistance at the solder pads.
I should have removed the doghouse before disconnecting all the power supply connections and pulling bad capacitors and resistors; I could have tested the voltage drops beforehand. The condition of the solder pads and traces was so poor I didn't want to try to desolder them intact, so I clipped them off and desoldered the remaining clipped leads, which preserved the traces.
As it turns out, as I'm sending the unit to Anatech, I have also stripped of other components that will be replaced. I just don't have the engineering skills to figure out the circuit and various alignment procedures without the schematics and service manual, but your responses have been appreciated and could be of help to others.
The preamp sounded much better than it should have for the poor condition of the components - must sound very good indeed when operating properly.
Rayma - they are wired in series.
Counterpoint mounted these Zeners beneath a plastic doghouse. The heat was effectively trapped, which cooked the bottom of the board even more than the top for some reason; I suspect the solder joints weren't great and there was added resistance at the solder pads.
I should have removed the doghouse before disconnecting all the power supply connections and pulling bad capacitors and resistors; I could have tested the voltage drops beforehand. The condition of the solder pads and traces was so poor I didn't want to try to desolder them intact, so I clipped them off and desoldered the remaining clipped leads, which preserved the traces.
As it turns out, as I'm sending the unit to Anatech, I have also stripped of other components that will be replaced. I just don't have the engineering skills to figure out the circuit and various alignment procedures without the schematics and service manual, but your responses have been appreciated and could be of help to others.
The preamp sounded much better than it should have for the poor condition of the components - must sound very good indeed when operating properly.
I just got an SA-5000 in for service. It basically works, a couple of noisy switches, the tubes are shot as are the rubber isolators that the circuit board floats on. These particular isolators are not made anymore so I'll have to figure something out. Maybe Chris has a solution for these.
Craig
Craig
There are lots of versions of these around.
https://www.amazon.com/Isolate-Sorb...ocphy=1028111&hvtargid=pla-311875000259&psc=1
https://www.amazon.com/Isolate-Sorb...ocphy=1028111&hvtargid=pla-311875000259&psc=1
The isolators Counterpoint used are much more elaborate than rubber washers, they are more like military/aerospace type stuff. I looked up the company that made them, Barry Controls, mostly military/aerospace.
Craig
Craig
Sorbothane is not rubber, and the ones in there could long have been out of production.
They certainly were not custom made for Counterpoint.
They certainly were not custom made for Counterpoint.
Barry Mounts won WWII for us. Engines and radios and surplus for decades.
They change the name once in a while.
dB Engineering – No Vibration.com
Hutchinson Standard Anti-Vibration Isolators - HUTCHINSON
Barry Engine Mounts | Aircraft Spruce
Barry Mounts - Google Search
Also sometimes "Lord Mounts", a competitor.
Vibration Isolators | LORD Corp
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