shiva 20th help needed

[mesabog]

amp is a little over 1 year old, both channels sound weak volume wise. dirt channel sounds fuzzy with little to no sustain ,hard to get the amp to feedback anymore. but here is the the deal,when i patch the rack send and return with a cable the amp sounds loud as hell again,crisp with sustain and feedback and clean is sparkling again. pedal send and return has no effect sounds terrible. power tubes have been replaced but no change in sound. without any loop used i have to run master at 1 oclock and channel master at 12 oclock just to get decent volume at practice. (and thats not very loud) with rack loop used master at 8 oclock and channel master about the same. i know the rack is +4 or something but the amp sounds normal like it used to running this way. tried calling bogner but still have not heard back yet

 

[glip22]

Did you try new preamp tubes? The loop is acting like a boost. I'm sure its a bad tube/s

 

[mesabog]

preamp tubes came in today, will try that and report back.

 

[glip22]

preamp tubes came in today, will try that and report back.

Should fix it. If not try cleaning all of your jacks with non residue contact cleaner. Is your head an earlier 20th? If so the effects loop jacks are labeled backwards.

 

[pedal builder]

definitely sounds like the effects loop jacks need cleaning

 

[mesabog]

preamp tubes made no difference, cleaning the loop jacks made it better not 100% but volume came up a lot.. i still dont understand the deal about the loop causing problems when nothing is inserted in it. does anybody else get a loud pop the firstb few time the boost is used reminds me of the mesa boogie pop on the rectos,must be a relay or something thats normal?