Very loud hum/buzz during a gig - standby on/off stopped it

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MJ Slaughter

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Oct 30, 2007
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Location
Dallas, TX
This last weekend during a gig my Mesa DC-5 started a very loud hum/buzz, similar to the sound of a guitar cord plugged into an amp and the other end touching something metal but it was quite loud. I turned the amp to standby then back on again and it was alright again though it did act up one other time during the night but the standby on/off worked. I had this same problem a few months ago so at that time I cleaned all the pots, jacks, tube sockets, tightened the sockets and put new power tubes in.

Where should I look for such a problem and why would turning standby on/off cure it, at least temporarily? Unfortunately I didn't have the chance to troubleshoot anything while it was happening. The club probably wouldn't have appreciated that.

My complete setup is the DC-5 with a GT-100 connected via 4CM with a Banshee talkbox. Guitar>Banshee>GT-100>Mesa.
 
this remind me when loosing bias current on a power tube, big hum and glowing tube!

there is a 5w resistor to the -49v power supply of the bias, this resistor is used to warm very hot, this + age this resistor solder on pcb worn, just get it to a tech to check tthis


regards
 
Thanks for the reply. I see the -49v at two 150k resistors in series. I'll check the health of the resistors and solder, after draining any voltage.
 

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