VHT PITTBULL CL50

[dpm309]

I am working on a 2000 Pittbull CL50 amp that sounds flabby, low volume, and extremely distorted. The owner changed all of the tubes and a visual inspection of the board did not reveal anything out of the ordinary. The filter caps looked fine also.  From what I can tell on this amp, they use a DC heater supply on the preamp tubes V1, 2, and 3 and AC on the rest.  I have had no luck obtaining a schematic since Fryette does not give these out.  Here are the voltages I recorded so far.  V1, 2 and 3 are for the gain stages and tone controls and V4 is the phase inverter.
 
Tube              P1       P2      P3        P4        P5        P6        P7        P8        P9
V1 ECC83        224     -       1.99        -        12.6     207        -        1.7       6.4
V2 ECC83        259     -        2.0        -         12.6    286        -        3.1        6.4
V3 12AX7        171    -         1.4        -         12.6    357      171      171        6.4
V4 12AX7        75      -        3.2      3.3AC    3.3AC   233       90      172          -
V5 6L6            -        H        429       429       -50    -            H            -        NA
V6 6L6            -        H        430       430       -50    -            H            -        NA
V7 5U4GB         -        -          -       356VAC    -    370VAC    -            430        -
 
Do these voltages look right?  Should the voltages be that high on Pins 7 and 8 on V3 and 4?

Thanks,

Dan

[dpm309]

I rechecked the voltages on the PI (V4) and here are the revised values:

  214   -   1.8   H   H   306   27   104   H

Dan

[chocopower]

V3 - pin 8 is ok if that triode is working as a Cathode follower. If not, there are a problem there.

Without schematic is hard to say.

[dpm309]

I found an open resistor connected to Pin 8 of V3.  The resistor is rated at 200k Ohm and I do have some 220Ks on hand.  Would this be an acceptable substitute?  Could this be causing the low, distorted volume?

Dan

[chocopower]

it work. It´s gonna decrese the gain a little, but, maybe, you like it.