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#1 2017-07-21 10:58:49

New member
Registered: 2013-03-22
Posts: 2

Ampeg V2 problem around 6K11


I've just finished the restoration of the V2 of mine.
I've done an extensive job, changing all the electrolytics and testing every resistors and coupling cap for proper capacitance and isolation resistance.

The problem that the signal stops at the second stage of V201 (6K11).
I've taken some measurements of DC voltages.

PSU   E=246V  D=335  C=404  B+=521
These voltages are on the low side because I'm in Italy and I'm using a step-down transformer that gives only 110V.

6k11     1(fil) 2(273) 3(37) 4(287) 5(292) 6(2.25) 7(0) 8(0) 9(292) 10(278)  11(32) 12(fil) 

These are higher in respect what stated on the schematic.

Lifting one end of C201 and C202 doesn't change nothing.
Swapped in another 6K11 from my nice sounding V4B and nothing has changed.

Following the original service manual from ampeg I've injected a 400Hz 470mV directly on pin11 and this is what I have:

6.8V on Pin2 (instead of 100mV)  6.8V on Pin7   and almost nothing on Pin5 instead of 5.2V.

I guess the problem is in the midrange circuit.
The tone stack board is the one with three discrete inductors instead of the toroidal one.
I have no LCR meter so I'm able only to measure the DC resistance:

L101 Orange 210 Ohm
L102 White 53 Ohm
L103 Green 171 Ohm

I'm quite puzzled.
Does anybody knows what It's goin'on here?

Last edited by Fefo72 (2017-07-22 09:40:48)



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