V4 PCB component repair/updating

[Hangman]

the small silver guys are the coupling caps. I'm not familiar with those particular caps, so I can't say how reliable they are. probably wise to replace. The small grey caps are cathode bypass caps, they are electrolytics and should be replaced. The larger silver one is the filter cap for the bias supply and should also be replaced. 100uf 100V in your amp. (later v4s had 2 10uf 100v)



The burned spot on the main pcb is not uncommon for these early V4s. in later version of the V4 they moved r53 over by the 3x40uf 500V capacitor that is on the other side of the chassis, near the Output transformer.
you can see if the board cleans up a bit there... but it is likely permanently discolored.
if it really bugs you... go to ebay
http://www.ebay.com/itm/Ampeg-V2-V4-VT22...3f361517ec
our friends at Orville amp technologies have reproduced the original board. it is a very high quality exact replica.

basically ampeg put too many hot components too close to one another. all of those resistors generate a fair amount of heat. my recommendation is to move R53 over by c17 (by the OT) when ampeg did this they added a small terminal strip.

if you are replacing the 10ohm resistors anyway... lower the resistance on them a bit... that will help keep the heat down there too. some people completely remove them... others change to 5.6ohm (like in later v4s) or even go as low as 1 ohm. I don't think the value is critical, but don't take it higher than 10 ohms.

some people update the diodes to faster diodes... but it isn't needed.

the striped film capacitors should probably get replaced. (often they crack)

hope that helps!
-steve

I got a V4 project that I'm getting ready to order parts for. I already have plans to redo the filter caps, screen resistors, plate resistors.

I had been told that the coupling caps sometimes need replacing. Are the coupling caps in these pictures the small silver caps on the big PCB?

Also, you'll see a burned spot on the big PCB near the screen resistors, the resistors don't seem to be compromised but I wonder what else there is.

Anything else that should probably replaced/updated? Diodes.

I'm also going to replace C16.