Vibrolux problem - sudden drops in volume

[foo3001]

I got this beautiful ´76 Vibrolux, and recently it has showed a strange symptom.

When playing the ´vibrato´-channel, there´s been random drops in output volume. Sometimes it fades out almost completely, and sometimes so that it´s barely noticeable. I haven´t noticed any problem with the ´normal´ channel.

It usually happens when the input signal is quite loud, for example a fuzz pedal at full blast or an OD + a booster pedal.

It´s gotten new power tubes and a rectifier tube recently, and the problem didn´t fix itself with them changed.

Where could I start hunting for the problem? My tech couldn´t find the problem (of course the amp worked 100% when it was in the shop for repairs....), he thought it was the rectifier tube as it was going bad but apparently it wasn´t..

 

[B Bent]

Re: Vibrolux problem - sudden drops in volume

Two things... does the light turn off as well or is it only volume drop. Mine will do that sometimes, but it seems that when i as much as breathe on the fuse holder it comes RIGHT back on. I would check that or the rectifier tube and power tubes. Keep me posted fellow Vibro brother!! :beerchug:

 

[foo3001]

Re: Vibrolux problem - sudden drops in volume

Two things... does the light turn off as well or is it only volume drop.

Nah it´s just a volume drop.

And the ´normal´ channel works fine, so I highly doubt it´s either the fuse, power tubes or the rectifier (the rectifier was changed after the problem showed itself the first time).

This is driving me crazy, as I really love this amp.. I want it to work 100% so that I´m able to bring it to any gig without having a fear of it failing on me...

...off to the tech it goes tomorrow.. Hope he finds the cause this time! If you guys have any suggestions what it might be / have had similar issues any info would be greatly apprecciated.

 

[doveman]

Re: Vibrolux problem - sudden drops in volume

Filter caps maybe? But that would effect both channels. Old amps that have not been played very much for a time period can have this problem.

 

[Smilemon]

Re: Vibrolux problem - sudden drops in volume

Input jack? When my pro junior gets Cranked it drops in volume, the jack rattles loose and barley makes connection.

 

[SlyFoxx]

Re: Vibrolux problem - sudden drops in volume

A bad pre-amp tube? But a tech should have caught that...hummm. Good luck.

 

[Bludave]

Re: Vibrolux problem - sudden drops in volume

It may bo something as simple as a dirty input jack. I used to have that problem with my Marshalls effect loop. Volume would just die out. I used a allen wrench and wrapped emory paper around it and push/pulled it in and out of the input jacks and the amp has been fine ever since!

 

[Jeffrec]

Re: Vibrolux problem - sudden drops in volume

I used a allen wrench and wrapped emory paper around it and push/pulled it in and out of the input jacks and the amp has been fine ever since!

Whoa Dave! I think I need a cigarette:laughing: Ever thought of writing for Penthouse?:bigok: