vaccastracca

Thank you very much for the prompt response to my message Yann! :-) Today I could phone a very good tech i know (unfortunately he lives 600km from me so i cannot bring him the head)...i described him the situation and he said it sure is a faulty integrated circuit in the preamp section. Cheap part. But lot of work to get it changed! Which translates in a "lot of money to spend" if i bring it to any tech in my area! So I'm considering the option of disassembling the amp by myself and maybe try to change the faulty chip with a friend of mine who is very good with soldering instrument parts etc... I carefully inspected your pics, and it looks it's really a big task to disassemble this amp!!! I guess the preamp section is in the front...which disassembly-order should i follow to take the frontal part out? ...it seems there are many small parts to take out one by one...and what I'm most worried about is the chance of unintentionally stretching some cable and maybe even breaking something!!!

Hello everyone. Sorry to burst in, but since I just got the same head, and I'm having some similar problems, I thought I might share the experience, in case someone has some tip! I write from Italy, and like Yann, I don't like the idea of giving the Mark IV to a technician...in my case it's not a matter of trust (I trust my tech), but it's just he's terribly expensive, so I usually go to him when there really is no other chance! Here is the issue: the graphic EQ, when engaged, causes a HUGE loss of volume. We're not talking of a few dB. It goes down to less than half of the volume you're using! Besides the volume loss, the tone also becomes very muddy and dark. The issue is the same on both channels. Other than this, the amp works totally perfect in every aspect, and sounds awesome.