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|8th December 2013, 03:05 PM||#1|
Join Date: Apr 2011
Location: Ankara, Turkey
Rebuilding Counterpoint SA-5.1 PSU
I'm a newbie and need your help for rebuilding the PSU of my Counterpoint SA-5.1. This is what I'm talking about:
And this is the schematics for it. Remember, Counterpoint schematics are known to be different then what is really inside. That's the beauty of owning a Counterpoint
My starting point was to replace the first 100uf cap with a smaller value cap due to recommendations of Counterpoint experts here. As you see in the schematics, that cap is the first cap after the 6CA4 rectifier, and exceeds the datasheet values of 6CA4 tubes. Searching for a cap is slippery surface when you have little criterias. At some point I decided to use a film cap at due to the small PSU chassis of SA-5.1 I decided to built a new one from the beginning. This is the original PCB of the PSU. It had some works on it, left from the previous owners:
I'm lucky enough to have a new designed PSU board by our member Pars. He made some corrections to the original design. I'm planing to use this board on my rebuilt:
In my built I'll use a bigger chassis than this one, so I'll have plenty of place.
One of the changes I'm planning is the circuity at the main power switch. SA-5.1 is always on, to keep the heaters powered whenever the preamp is plugged in. The power switch controls the power to the heater on the rectifier tube only, which then powers up the HV section, and turns the preamp on. Our member VivaVee and Pars suggested a delay circuit which will turn on the heater immediately and HV section after a delay. VivaVee also suggested the Morgan Jones book but I'd be glad to hear any more help.
I'll change the electrolytic capacitors to film caps, add a IEC plug to the back. I may consider to omit the PCB and convert it to a point-to-point wiring, but I'm not experienced enough to do that.
Since there is a big transformer along with a 6AC4 tube in this case I want to add a thick enough case on the xfrmr to shield it. BTW, I'll use a Plitron toroidal xfrmr in the new PSU. I ordered Ott's book and looking for a bargain copy of Morrison's book.
Ok, let this be a start to the topic. I hope the helpful people on this forum join to this conversation.
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