EQ Board
I know I'm doing things bass ackwards by recapping, etc the different boards vs getting the amp boards functioning 100%, but methodology will now be the next project. Yesterday's work was the EQ board. Easiest access was desoldering the two pins from the trace side which had brown and white wires attached. The remaining ones could stay attached as there was plenty of wire slack now. Caps used were a mixture...Cerafine for one of the 3.3uF/50V caps (FG the other to be consistent with the experiment), ELNA RBS (Silmic Bipolars), Panasonic ECQ film to replace the 1uF/50V CEANL caps, Panasonic FC (47uF/50V) and United Chemicon 470uF/25V with 0.1uF/50V ECQ bypass.
I again replaced a bunch of resistors just because I had the Dale MFs and was able to match them. The ones I din not replace were due to not having the value (or close enough) on hand.
I also replaced the Qs per the suggested ones and hfe-matched the new ones as best I could. Interestingly, Q1-Q4 (2SA725P) had orange dots on the tops, I'm assuming meaning they were either originally matched or selected for low noise (sort of like they did with certain preamp tubes that had painted tips). Here's how they measured:
Q1 - 470 Q2 - 510
Q3 - 460 Q4 - 530
I'd say the matching was OK for each pair, but nothing was done to keep each channel pretty close (like a matched quad of tubes). I don't know whether it was all that important, but I was able to get 4 KSA992Fs matched at ~ 520.
The others Q5-Q10 (Q5,7,6,8 - 2SC1919, Q9,10 - 2SA726) were all over the place:
Q5 - 755 Q6 - 644
Q9 - 420 Q10 - 323
Q7 - 630 Q8 - 550
These got replaced with KSC1845F and KSA992P. Why the different hfe groupings you ask? My 1845s, even though they were "F" (300-600 hfe) were reading <= 420 whereas my KSA992Fs were in the 500-600 range. Since the 2SA726s that were pulled measured lower than the 2SC1919s, and my "P" KSA992s measured on the high end of their 200-400 hfe range, I decided to save the higher measuring "F"s for other projects.
So, my Q5,7 and Q6,8 measured ~ 410 and Q9,10 measured ~ 385, thus keeping the KSCs with higher gain than the KSAs.
Again, for those trying this at home, make sure to insert the Q's observing proper polarity: the originals are BCE and the replacements are ECB. Also reflowed the rest of the board and added a touch of solder to all the wirewrap posts after a light Dremel wire brushing.
Some shots:
Overhead
Oblique