mark IV power loss

Pre Recto days. Boogie modified Fenders, Mark I-IV, Dual Calibers, etc

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Single Recto
Posts: 1597
Joined: Sun Aug 13, 2006 1:21 am
Location: Hinesville, GA

Post by disassembled » Sat Mar 10, 2007 9:01 pm

I would say the first thing that you need to do is what BB suggested: plug a cable from the Effects send to the return or simply turn the effects loop off from the footswitch. After you determine the loop is working then you should start trouble shooting. I don't think that V5 is a problem either since the amp works fine with the triaxis in the loop which says: the return jack, PI tube, and output tubes are all working.

Replacing the jacks every couple of years is unnecessary maintenance as a Q-tip with some alcohol with clean them right up. It's just a bit of dust that gets in there and breaks the connection to make the amp thing there is a cable plugged into the jack. Every amp with a serial loop potentially faces this problem but it is an easy fix.

Arigato gozaimas!

Mark IV
Posts: 934
Joined: Fri Jun 30, 2006 7:00 pm

Re: mark IV power loss

Post by igfraso » Sun Jun 11, 2017 12:02 pm

Boogiebabies wrote:A bad phase inverter or possible the master volume pot.

Most likely, the PI. When you turn the amp off it kills the voltage to the tubes and it may come back to life after the recycling of the power.

A good pot cleaning would not be a bad idea anyway. They get dirty and scratchy after only a few years of use.
I have been having the same problems with my Mark IV-A as the one reported by the original post here. I was also finding it was solved by flipping the stand by switch.
Thank you Boogiebabies for your note. I will replace the PI tube and clean the master volume pot and the effects send and return jacks.

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