Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on May 15, 2011, 02:57:28 am

Title: MSJ SOUNDS Grrrrrrrrrrrrrrrrrr8
Post by: TIMBO on May 15, 2011, 02:57:28 am

Hi guy's, Done some tiding up on the Silver Jubilee and took voltages, all seem to be OK but don't have anything to compare them too. The reverb is from Tubenit's FX unit and some voltages differ to what i have.

                        P1       P2      P3      P4      P5      P6      P7       P8
V1 12AX7          166               1.66                      147              1.27
V2 12AX7          158               1.31                       91               0.33
V3 12AT7          276 (277)       13.37 (4.9)             267 (277)      13.37 (4.9)    Bracketed Tubenits voltages
V4 12AX7          124 (165)       1.11   (1.3)            124 (165)      1.11  (1.3)
V5 12AX7          254     14.8     48.1                     236    16.1     48.1
V6  EL34           33.3               429    424    -29.4                      33.3
V7  El34            33.5               431    427    -29.6                      33.3

VVR  41 -> 417
Node A - 430
        B - 428
        C - 394
        D - 254
        E - 237
        F - 285  (12AT7 Reverb)
        G - 264  (12AX7 Reverb)
Voltages taken when switched to FIXED BIAS
BIAS setting -35.8mV
I don't know if the voltage reading on the cathode of the 12AT7 is right but i did check it twice.
I'm using a short tank and the reverb does not have much effect. Any thoughts.

Thanks

Title: Re: MSJ SOUNDS Grrrrrrrrrrrrrrrrrr8
Post by: tubenit on May 15, 2011, 06:05:14 am

Per the schematic that you posted, those are NOT the values I used for my FX-Reverb unit.

I would think the 3300k (3.3M) resistor and .1 cap instead of .01 would definitely impact the reverb.

With respect, Tubenit

Title: Re: MSJ SOUNDS Grrrrrrrrrrrrrrrrrr8
Post by: TIMBO on May 15, 2011, 02:17:24 pm

Thanks Tubenit, I'm a goose ,when i drew my schem i've put in the wrong values.The 330k is right but the .1 cap should be .01.I don't have a 2.2m pot so i'll see if changing the caps will work first.Thanks