Mark IV volume cutting out

[Pmaurer]

My buddy has been visiting me and he brought his Mark IV rackmount with him. Recently he's been having volume issues. We can play for about 5-10 minutes and then out of the blue the volume drops out and you can barely hear anything...then 1 minute later the volume will randomly jump back up to how it should be. This happens on all channels. He completely re-tubed it with new preamp and power tubes (mesa JJs and 6L6's). The only "fix" for it seems to be putting it on standby for a minute but this only holds its ground for another 5 minutes before the volume goes all wacko again!

 

[primeholy]

My buddy has been visiting me and he brought his Mark IV rackmount with him. Recently he's been having volume issues. We can play for about 5-10 minutes and then out of the blue the volume drops out and you can barely hear anything...then 1 minute later the volume will randomly jump back up to how it should be. This happens on all channels. He completely re-tubed it with new preamp and power tubes (mesa JJs and 6L6's). The only "fix" for it seems to be putting it on standby for a minute but this only holds its ground for another 5 minutes before the volume goes all wacko again!

Quick fix? Put a patch cable from the send to the return in the effects loop. If that works (even if not) get a can of electronic cleaner and spray in the loop jacks (with amp off) and repeatedly insert and take out a 1/4" plug into the jack.

 

[Boogiebabies]

If it's the loop, all you need to do to test it is turn it off. The MK IV loop is all controlled by LDR's so the signal will only get cut off
if something in the loop was dead. Two LDR's close to open the loop and one opens to short the original signal. With the loop off, one LDR closes
to carry the original signal.

Jiggle the master volume pot when it cuts out to see if it's a bad switch for the pull silent.

 

[bryan_kilco]

my IV did this to me once about a year ago at a show, then never did it again. I always seemed to have issues at that venue with my amp powered on, then im setting up the rest of my stuff and notice the amp is off....so i jiggle the plugs and connections and nothing, try swapping to different outlet...nothing.....keep messing, then BAM - working again.... also the volume was dropping a significant amount and did this the entire set every few mins or so. after that, never happened again.

 

[primeholy]

If it's the loop, all you need to do to test it is turn it off. The MK IV loop is all controlled by LDR's so the signal will only get cut off
if something in the loop was dead. Two LDR's close to open the loop and one opens to short the original signal. With the loop off, one LDR closes
to carry the original signal.

Jiggle the master volume pot when it cuts out to see if it's a bad switch for the pull silent.

I didn't even think about the loop being off. Thanks :thumbs: