Help! Blackfacing a Bassman/Bias Conversion Question...

Hey guys, I have a few questions. I have a '68-ish Bassman (AB165 circuit) on my work bench and I'm in the middle of changing the bias set-up to blackface specs. I ran into a problem and need answers.

Ok, I removed all the resistors going from the bias pot to the main circuit board. On the pot, I have one lug with a wire going to the bias board, one lug with a resistor soldered to the back of the pot, and one going to the main circuit board. I have read that all I need to do now is install the two 220K ohm resistors going from that junction to the top of each cap sitting there. Is that it? Note I have already removed the single original resistor on the right side of that junction.

My real problem is, the AB165 uses two .022uf caps at that spot while the AA864 uses two .1uf caps. Can I leave the original caps there, or do I need to swap them out with the .1uf units??? This is a pic of where I stand now. I'm ready to shorten, bend, and install the two new resistors...




While I'm at it, here is another question. The two 220K resistors that lead to pin 3 of each power tube...Keep them or remove them? The ones that are up on the little lug below the bias area I'm working on. AA864 does not have them, should they stay or go?

The info I have been working from was on the Hoffman Amp Board. Here is that link.

http://www.hoffmanamps.com/bias_conversions.htm

Thanks,
Dan

 

Thanks Guys.

Ok, lets see...Yes, the amp is a '67. It belongs to a friend and when I got a hold of it, the only things that were not 100% stock were the main a/c switch was an older replacement, and 1 resistor had been chaged. All else looked original.

The plan was to BF it and give it a tune up. After he had it a while, we decided to hold off on the full BF treatment because he liked the stock tone.

Anyway, I have already replaced the filter and power supply caps and resistors under the "doghouse". I also replaced the cathode caps on the board along with a "deep" switch that was faulty. I have a 3 prong cord ready to install as well. I just need to finish up the bias mod and I'm ready to turn it back on and give it a test (once I buy a bias meter that is).

Once I get it running, then I will consider mods including cap/resistor value changes and messing with the feedback circuits. I just wanted to verify that I was doing the bias mod correctly.

Most of the caps on the board are the blue Mallorys and that is why I'm not in any hurry to swap them out. The three right next to that picture are the brown turds, but the rest are Mallorys.

Doctorx, what resistors are you talking about changing to 100k and 82K, and what will that do for me?

Thanks,
Dan