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Pilot 232 Power Supply Help

E

ellensdad

New Member
I am thinking about fortifying the power supply on my 232. Admittedly, I have a very basic understanding of electronic schematics as will be confirmed by this question. Is C33A the first filter after the GZ34? I'm not sure I am up to taking this work on myself but I would like to understand the schematic when I talk to a tech about the work.

Schematic:
http://www.vintagevacuumaudio.com/schematics-manuals/pilot/pilot-sa-232-schematics.pdf

Thanks in advance for any help.
 
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Honestly the power supply isn't too badly set up on these. If you wanted to make a change, I might consider replacing R94 with a choke that has suitable ratings. That would give you better filtering, and if you got the dc resistance value of the choke right the voltage wouldn't change by any appreciable amount. Don't know if there is spare room for a choke on these though.

Don't bump the value of that first cap too much either. Its stressful for the rectifier. Off the top of my head I think 60uf is absolute max on a 5AR4, but honestly you'd get better results from a filtering standpoint leaving the 40uf first cap alone and increasing the value of the one after R94. It would also make life on the rectifier easier.

Something else possibly worth considering is Dave Gillespie's EFB setup. Basically itt replaces the cathode resistor with a fixed voltage regulator that tracks the plate voltage, keeping the bias set as a fixed percentage of plate voltage. What you get out of it is reduced distortion and improved power output, especially when driving both channels.

http://www.tronola.com/html/a_new_look.html

Thats written specifically about a Dynaco amp but the idea is the same and the amps are broadly comparable.
 
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Thanks for the help guys. I have read about other 232 owners doing the following with positive results:

C33A-32uF Poly
C33B-220uF
C34A/B - F&T 2x100uF

Regarding the choke, it's pretty tight in there but it sounds like an interesting idea.
 
Don't get sucked in by some guys "re-engineering" what Pilot did years ago. Remember that the unit was designed by engineers. Often, we have armchair "experts" who, after the 4th glass of red wine think they knew better. I think that what the came from the factory is what will work.

However, "Your mileage may vary".
 
Keep in mind, the engineers of yesterday were constrained by the technology of the time as well as the bean counters only concerned with the bottom line. There were lots of compromises made, if this were my amp and the caps needed replacing anyway why not upgrade a bit?
 
Using a choke will certainly help to reduce ripple in the power supply without negative consequences. But as mentioned, you don't want to go high on the first capacitor after the rectifier. No argument there.
 
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