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#1 2014-02-05 02:09:17

New member
Registered: 2011-09-20
Posts: 6

Ampeg V4 Plate Voltage

Hello All!!

I have a V4 that I am trying to bring back to life. When I got it
all power tubes were fried. Replaced all Filter Caps with F&T . Rebuilt bias supply (changed 0.047 cap, resistors, and 10uf electrolytic with Spragues) I re-flowed all ground connections on the ground bus and cleaned the input jacks with DeOxit. Fired up the amp. Amp has some 60 cycle hum. Hum balance pot does work. My bias voltage is -60v . Plate Voltage is around 517 and screen voltage is close to that. Is this normal? What would cause a lower plate and screen voltage. I have at least 120v coming out of the wall here.

When the standby switch is put into the play mode there is pop and when the switch is put into standby mode it makes two fast buzz notes through the speakers. The Standby switch is a 6A Carling but it may be original.

When the power switch is turned there is a small audible buzz through the speakers. Is this normal?

This is my second V4. I haven't got my other one to be stable yet. The board is quite messed up. Lots of lifting pads. I would love to tame both of these beasts.

I have learned so much from this site/forum. Thanks y'all!

I can post pics if needed



#2 2014-02-15 14:56:05

New member
Registered: 2013-07-29
Posts: 1

Re: Ampeg V4 Plate Voltage

Both of mine pop if the volume is on when I turn off the stand by.  I allways leave the stand by up until I am ready to turn on the amp.

As for the 60 cycle hum I would look at lead dressing( my v-4b had nasty hum with the Mids boosted, I moved the leads to the 6k11 board and it went away).  If that doesn't work look at coupling caps(all of them).

I would also check out the solder joints on the sockets.

My power tubes seem much happier with the 1k5watt resistors in place of the 470 3watt resistors.

I'm no expert but these beasts can be tamed.



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