I've got a pair of PCBs in front of me with the schematics. The listing for the 100K 1w is incorrect,
on the schematic of the PC-6 phono board the 150K is marked as 1w. The actual boards I have in front of me
has a 1/2 watt resistor on it, it's 40 years old, doesn't even look like it ever got warm.
Using the voltage chart from the PAS3 manual, that resistor has 95v across 150K equals .63ma and
that is .06 watts. The one resistor with the most power across it is the 100K plate resistor on PC-5 line amp.
It has 130v across 100K for 1.3ma and that is .169 watts, about 1/3 of 1/2 watt rating.
On the actual boards I have in front of me that 100K is a 1w resistor even though the schematic doesn't
spec that. It is an original part. None of the cathode resistors use more than .06w - See updated board layouts below ...

Roy @ www.tubes4hifi.com

This is a great resource if building a PAS with the tone controls and filters. Generally when rebuild a PAS, I bypass the tone controls, take out the blend, loudness and filter switch. This cuts down on the components considerably. My question is what components can be left off the board if these features are not used? I modified the attached schematic and think got it right but am not sure if I took too much out or not enough. Does this look correct?



Original



I am currently jamming a PAS3 board into a SCA-35 that has been modified with ST-35 boards and the phono stage removed. Its really a Dynastein amp, I will post some pictures when its all done.

looks good to me. BTW, I absolutely hate trying to read the PAS schematics, probably the worst set of schematics I've ever seen in my 40 years of electronics. I have redrawn them to be readable if anyone wants them email me, I'd rather not post them here. You can eliminate the 510K on the output jack.
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