Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on September 25, 2012, 03:36:38 pm

Title: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: Colas LeGrippa on September 25, 2012, 03:36:38 pm

I HAVE THIS SHIT ON MY BENCH ( sorry I didn't want to shout that loud !! ). This amp has a reverb but no tremolo. Why does it act as if it was a super reverb with tremolo full open ?

There is some kind of oscillation goin' on somewhere, any idea ?

Colas.

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: plexi50 on September 29, 2012, 06:11:39 pm

All i can think of right now is maybe a wire some where is too close to another wire. I have seen this happen with the OT wires not twisted or too close to other parts. Could be one of your power tubes as well. Seen some strange things happen with power tubes once in a while

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: PRR on October 01, 2012, 12:55:17 am

Low frequency oscillation:

Power supply filter caps

Bad un-balance in push-pull stages

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: stratele52 on October 01, 2012, 06:08:42 am

Microphonic tube ?

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: Colas LeGrippa on October 01, 2012, 07:29:41 am

replaced filter caps, prob. solved, thank God ! :icon_biggrin:

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: stratele52 on October 01, 2012, 07:42:10 am

Bad filter caps sound like reverb ?

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: Colas LeGrippa on October 01, 2012, 08:42:33 pm

no Stratele, bad caps cause oscillation, like a tremolo, in the worst case I guess, I've never experienced that before.

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: stratele52 on October 02, 2012, 03:18:11 am

Quote from: Colas LeGrippa on October 01, 2012, 08:42:33 pm

no Stratele, bad caps cause oscillation, like a tremolo, in the worst case I guess, I've never experienced that before.

Same as me , never experienced that . Thank's

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: plexi50 on October 02, 2012, 08:17:25 pm

Another great example of how important the power supply caps are. They also can cause ghost notes and other weird tone issues. Glad you found it*

Title: Re: MESA BOOGIE caliber 50 WEIRD PROBLEM.
Post by: Colas LeGrippa on October 03, 2012, 07:09:45 am

thank you, everything is possible ''with a little help from my friends''. :worthy1: