loss of brightness?

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sendep7

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History: i bought this amp used. supposedly it was never gigged and sat in a studio its whole life. which is basically what i do with it. since the pandemic i've been using it in my bedroom through an orange 1x12 16ohm, i've been running it in 8ohm(combo mode)

a few months ago i was playing in full 90 watt mode but at a reasonable volume, and had a massive volume drop and the amp started buzzing and an electrical burnt smell(no smoke), so i quickly killed the power and let it cool down. apparently i had disabled the transformer fan at some point? maybe it overheated? after a few hours i plugged it back in. and ran through all the settings, recto modes, diode modes, triode/pentode, loop on/off all power modes, with with out sag and everything seemed ok.

today i was playing again in 90w mode on channel3 IV with bright engaged. after a while i noticed a slight loss of gain and input brightness? at first i chalked it up to switching tubescreamers out and bad cabling. but after going direct into the amp with short cables i seem to have some loss of brightness at the input? even with the bright switch on, and the tone knob cranked on the tube screamer, im fighting for sustain/attack.

is there some filter cap on the input that could have blown? i don't think its a tube issue they have low hours and havent really been pushed hard in their life.

any ideas would be helpful.
 
Howdy.

Burnt smell is usually not-good sign. Also some other things to check:
- dirty fx-loop connectors (test with patch cable)
- dirty tube sockets (tubes off, apply some electrical cleaner and insert/remove tube multiple times, let dry before powering up)
- broken/tired speaker out jack (Test speaker connected to another jack)

If there’s been some issue producing bad smell I would take it to Mesa-understanding repair person :) just for peace of mind. Some early Mark Vs have had issues with rectification diodes.
 
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