Mods on a '78 Pro Reverb - need some help!

8/19/2000 3:43 AM

CW

Mods on a '78 Pro Reverb - need some help! I'm working on a friends 78 MV Pull Boost, Hum control, Bias balance Pro-Rev. He wanted it Blackfaced, so I used the first 3 steps out of G. Webers book chapter on conversion of SF to BF Twin Reverb. I know they are a bit different than what I'm working on. Adj bias works good and MV was removed. Didn't do step 4 because the resistor values under the filter cap pan he says to swap(2.2K and 10K) are not the stock ones in this amp(4.7K and 1K). The normal channel volume now seems to be at about 50-60% strength of the Vibrato channel at the same settings. Kinda weird. I checked the pre-amp voltages and they all appear to be OK with the exception of V6A/B at 221 & 210 respectively. Tonight I put in a NOS GE 5751 and it juiced the volume a fair amount.   Am I dealing with too much of an apples/oranges circuit issue or is there something I might have grossly overlooked? I'm hoping some of you pro's out there can straighten me out.   Thanks much!   CW