Fender Blues Deville cutting in & out at volume...help!

[slapbackdaddy]

Hi all,

This is my first post here and i hope someone can help. I have a Fender blues deville that has recently started to cut the signal in and out (just for a second or so at a time), the problem is worse as the amp is turned up higher or more specifically when driven harder at volume, for example if i run into the first channel, set the volume at between 4-6 and back off the guitar volume it'll generally be ok but as soon as i turn up the guitar volume say for a solo it'll start cutting the signal in and out. It seems to be a soft (but quick) drop in and out, not and instant drop off like you'd get from pulling your input jack in and out of the guitar socket.
I've re-tubed the 6L6's and the 3 12ax7's have all been A/B'd with other 12ax7's but it has made no difference.
Am i hearing a resisitor or cap breaking down on the output tubes perhaps???

FYI, the problem is the same with different guitar cables and different guitars.

Anyone come across this problem?

[Euthymia]

Do you have a separate speaker you can plug the amp into?

I ask because your problem could be due to mechanical vibration, which of course increases as you play louder.

That series of Fenders is known for its solder joints breaking down.

When it cuts out (or even before), try pounding the top of the amp with your fist and see if anything happens.

[Don Moose]

The most problematic solder joints in these guys are the dropping resistors in the +/-16V supply.

On the Blues Deluxe schematic I have, they're R85 and R86 - on the Blues DeVille, look for the op-amp power supplies and work back up the chain to the zeners and dropping resistors.

Search here for Enzo trace pad - that should get you to a detailed thread on the topic.

Hope this helps!

[drewl]

definitely reflow the dropping resistor solder joints, pull the tubes and reflow the socket pc board connections also.

[slapbackdaddy]

thanks guys

I'll try to check out the dropping resistor joints if thats a suspect part of this amp. I've never taken this baby apart but from what i hear they can be a bitch. I'm ok with the electrical work, i've re-capped and done work on my older (non pcb) amps so i hope its not too much of a pain in the butt to get apart and reassemble. Do you know of any threads on disassembling a blues deville? I've done a google search but only found vague pieces on hot rod devilles.

As for the speakers, i checked over the connections, they seem fine. The signal loss definitely sounds tube / resistor related in the way in softly drops in and out.

Any more ideas please let me know. I've got to finish off a cap job on a silvertone 1482 today then i'll try and get to the fender over the weekend, i don't have any gigs till next weekend (first weekend off in 3 months...yipee...although i don't think my other half will be too pleased when she sees the toll box and soldering iron coming out instead of spending "quality time"!)

[R.G.]

The dropping resistors/zener power supply for the low voltage stuff is a major design flaw in these amps. The zeners should be replaced with three terminal regulators (7815/7915) and this would cut the power in the resistors dramatically.