Hello All,
Starting a upgrade project on my Counterpoint Sa3 preamp. Its been sleeping for over ten years, but now I'm pulling it out of the closet for use as a two channel vinyl (mostly) system for my new library/music room. Goal is to freshen up the gear I have to make a nice higher end system. Turntable is a modified Thorens TD160 with dampening ,custom base and carbon fiber top plate. The arm is a Magnepan Unitrac with Cardas wire, and a Grado Reference Cartridge. Initially I'm using a Musical Designs D75, powering Magnepan MG1's in a custom frame.
The plan for the counterpoint is to get it working and do some updates to the power supply , repair obvious damage to resisters and other components.
Starting a upgrade project on my Counterpoint Sa3 preamp. Its been sleeping for over ten years, but now I'm pulling it out of the closet for use as a two channel vinyl (mostly) system for my new library/music room. Goal is to freshen up the gear I have to make a nice higher end system. Turntable is a modified Thorens TD160 with dampening ,custom base and carbon fiber top plate. The arm is a Magnepan Unitrac with Cardas wire, and a Grado Reference Cartridge. Initially I'm using a Musical Designs D75, powering Magnepan MG1's in a custom frame.
The plan for the counterpoint is to get it working and do some updates to the power supply , repair obvious damage to resisters and other components.
Tonight, I hooked up the amp and fired up the counterpoint. Hooked up a Sony ES cd/dvd player to test it out. Good news, it fired up! The volume control was noisy but the amp was pretty quiet. I have never really used this pre before, I bought it and it went back into the back box when I moved. I found tonight that the pre doesn't output stereo and both channels output only when the mono switch selected. Also the Balance doesn't to work either.
I understand there isn't any real service or troubleshooting guides for this unit, so anyone with knowledge care to suggest a troubleshooting plan?
I understand there isn't any real service or troubleshooting guides for this unit, so anyone with knowledge care to suggest a troubleshooting plan?
Pictures of the project are on photobucket
Counterpoint SA-3 Project Slideshow by marktmeyer | Photobucket
Counterpoint SA-3 Project Slideshow by marktmeyer | Photobucket
Thinking either the Volume control pot or the input selector, or the input jacks might be the culprit of the no stereo issue.
Got my order from Michael Percy today, and the can of De-Oxit was in there. Not a moment too soon. cleaned every pot and jack with it, cleaned the volume control...
Silence , and two channel bliss!
Now I can start my planned parts upgrade. Took some voltage measurements and was a little surprised by the numbers. What little schema I can find indicates I should see 428v at the first Cap , seeing over 490volts there, on a rated 450volt part. Wow! second cap was over voltage as well.
So the plan is to start with the supply caps, and diodes. I have two 80uf 500v Jensen caps, and 220uf 385v ROE gold bullet caps with the 300uf Sprague being replaced by a 220uf 385v ROE and and 100uf 450v ROE. Upgrades to the Diodes will replace with UF rated 5408 and 4007s. Plate resistors and being replaced by 5w Kiwames. Next on the list is ceramic gold plated tube bases. Last and most important are improved input and output jacks.
Silence , and two channel bliss!
Now I can start my planned parts upgrade. Took some voltage measurements and was a little surprised by the numbers. What little schema I can find indicates I should see 428v at the first Cap , seeing over 490volts there, on a rated 450volt part. Wow! second cap was over voltage as well.
So the plan is to start with the supply caps, and diodes. I have two 80uf 500v Jensen caps, and 220uf 385v ROE gold bullet caps with the 300uf Sprague being replaced by a 220uf 385v ROE and and 100uf 450v ROE. Upgrades to the Diodes will replace with UF rated 5408 and 4007s. Plate resistors and being replaced by 5w Kiwames. Next on the list is ceramic gold plated tube bases. Last and most important are improved input and output jacks.
Test fitting the additional 80uf I'm putting in tandem with the last 220uF ROE to replace the 300uF blue Sprague.
Need to also replace the 1N5400 diodes tonight as well. One of the diodes looks like it has deteriorated , and worries me. The first 80uf orange Sprague also shows some
corosion as well. All of the voltages measured last evening were either at or above the parts ratings. No wonder these have a reputation for unreliability. All of the replacement parts are rated at higher working voltages than the current parts.
corosion as well. All of the voltages measured last evening were either at or above the parts ratings. No wonder these have a reputation for unreliability. All of the replacement parts are rated at higher working voltages than the current parts.
Changed two of the 200uF to 220uF ROE's bypassed with the .1uF relcaps, changed out the 80uF Spragues to the Jensens. Sounds good so far!
I've let the amp play for a while tonight, sounds pretty good needs to burn in, took voltage readings, and found that all of the power supply caps were back to expected levels. The first 80uf cap now read 375volts instead of nearly 495v. the others fell into line as well.
Tonight, I changed out the Sprague 300uF cap, Installed two ROE caps one the 220uF 385v and one the 80uF 450v. Finished the install and fired up the Preamp/system. Sounds better, but it seems obvious that there will be a long breakin period. Listening to Diana Krall's vocals it sounded a little honkie , So I decided to remove the rel-caps, and listen without any bypass caps. Much better! I can hear the sweetness of the tubes with much improved bass even through the tiny near field speakers I'm testing through.
With the Rel-caps:
and Without the Rel-caps
With the Rel-caps:
and Without the Rel-caps
Waiting for the Diodes and My replacement order from Michael Percy (with the Kiwames). Tomorrow, installing new ceramic tube bases, then on to Rhodium input and output jacks.
Got some resistors from M Percy yesterday, installed the 13k plate resistors for the line stage tube. Also while I was at it, installed the ceramic tube socket for the line stage tube. The amp sounds better each hour it plays. Voltages seem to be more stable, there seems to be less heat being generated.
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