Blackface Deluxe (Non-Verb) Distortion

[dhodgeh]

And not the good kind....

It's quiet when not playing, but play any notes or chords on my guitar, and sounds like a shorted cable connection. The cable is good, and the distortion comes through in both channels.

I swapped out the power tubes with a known good set, and the problem persisted.

I know a little bit about these things (I have assembled a 5E3 kit, and my own outboard reverb unit), but am no expert by a long shot.

Any suggestions as to where to start trouble shooting? I'm in North Central Florida, with no amp techs where I live.


TIA

D

[Justin Thomas]

Did you try the preamp tubes? Look at the back of the amp while it misbehaves. Any of the tubes sparking or flashing? Don't forget the rectifier tube too.
Set up a loop or delay & set it up so the amp misbehaves. Do any of the controls affect it? Which ones? Ball up your fist while it misbehaves & give it a firm whack on the top. Does this affect the noise in any way? (This is called The Enzo Whack in these parts, and is kinda patented. Or you can use a rubber mallet. Don't hurt yourself & don't break the amp of course.)

Also, R.G. Keen's Tube Amp Debug page is a great resource to start out. Geofex.com, look in top left corner & find "tube amp debug page." Follow links accordingly.

Justin

[Enzo]

Also, connect a different speaker to it and try. A broken tinsel wire on a speaker, or a rubbing voice coil could do this.

[dhodgeh]

Thanks for the suggestions.

The speaker is good, connected it to another amp and no problems.

I reseated the preamp tubes with no change.

However, I can get a fairly clean sound out of the normal channel, and am now noticing that if I wiggle, turn, tap on the volume pot for the vibrato channel, all manner of sonic hell breaks loose.

So, should I take a look at that pot as a possible problem?

Thanks

D

[Chuck H]

... if I wiggle, turn, tap on the volume pot for the vibrato channel, all manner of sonic hell breaks loose.

So, should I take a look at that pot as a possible problem?

Good start. It could also be a connection to the pot. Or even in the circuits connected to the pot lugs. They do move a little with the wafer when you tap the pot. The amp is tender enough that cabinet vibration when playing instigates the problem so you can't isolate the pot as the problem just yet. Opening the amp and poking/tapping at everything with a wooden stick is a common troubleshooting technique.

[The Dude]

......It could also be a connection to the pot......

^^^^^ Yes. That. Also check any grounds soldered to the brass grounding plate in that area (if it has the plate). They can crack loose sometimes and cause intermittent problems.