old mod headaches

[Andy Le Blanc]

I got this nice old vibrolux in the shop, the inside is mint... 6G11

But... at some point the opt got replaced with a one out of a dual-showman

it works, the loading and the tube compliment, etc...

But... it wont fit in to the cab with a modern speaker frame, its a mess.
half on half off the chassis... major wtf.

And... the owner loves it.

the easiest thing may be to fab a new speaker baffle, put the speaker over to the side and make some room.

Pain in the arse, it just needs new PS filter caps and its good to go.

[Stevem]

If it's not the stock speaker and it's the multi rear vent type will notching out one if the vents let you get the chassis into place?
This is what I had to do with my Vibrochamp to fit in a 10" driver and clear the multi cap can.

[Andy Le Blanc]

nope... thought about that too, everything lands in the wrong place and I'd end up cutting into the basket.

Cant mod the bells of the opt either... it got to be the most awkward thing I seen in a long while

[JerryFJA]

Can you front mount the speaker to gain a little room?

[Phil_S]

Show some pictures. Give us a chance to see something you don't. Couldn't hurt. Might help.

Maybe he just needs a new cab

[sluckey]

I'd hate to hack a nice old Vibrolux. Is using a proper sized OT not an option?

[Andy Le Blanc]

I'm with you guy's

I fab'ed a new motor board, looks good, the original will go with owner...

It all fits together now, and I'm working my way thru the rig, needs tubes but for the most part it looks good... voltages etc

till I go to play thru it... and this gawd awful distortion, even with good tubes.

major wtf... now what moment, no resolution... until I start to reexamine the bias.

And it starts to scream like a stuck pig, like the plate leads are reversed...AH-HA

it was biased so cold that wouldn't oscillate freely, just enough to totally frig signal thru... new one on me, learn something every day.

Hadn't seen that one yet, crap distortion, with no oscillation, with the plate leads reversed.

I'm beginning to think that it was an aborted mod... it needed filter caps
so the guy thinks its his opt, and screws the pooch.

I think it'll come off well.

[Andy Le Blanc]

Pict's of the rig..

The old motor board, the center placement just didn't permit the mod,
and, the old fender grill is just plain cheap, thin, thin, thin...

The new motor board with speaker place offset, everything fits.
Much heavier void-less material, the speaker is nice too.

I think I said it once before, it needed PS filter caps, and the mod was bauched, the speaker looks to be the latest attempt to resurrect the rig.

The inside is wonderfully clean the only real change I made was the bias resistor for the fixed bias supply,
I switched it from the 43k from the 6g11 to the 33k in the 6g11-A

I put bleeders on the screens to make sure they were operating just negative to the plates with the hotter bias.

And the reassembled chassis with the ginormous OPT...

nice sounding rig, the client will be jazzed.

[Andy Le Blanc]

And one more thing I keep noticing...

I'm perpetually running across incredibly low numbered rigs.

fluke of regional distribution maybe.

[Structo]

Whoa!

#2?

[Andy Le Blanc]

I had princeton #7.... harvard # 12

damnedest thing.... And not just fenders, I see the weirdest old transition models, the unidentifiable gibson.

I do know that the region has had a very long term entertainment market north of Boston up thru the Maritime's.

I love to know why, I've been thinking it goes back to consumer radio dealer and distribution deals back to the 30's, but its just reaching for straws

[Andy Le Blanc]

The client is happy happy happy... I'm happy too, had fire wood delivered yesterday.

I dont see that opt mod too often, folks usually trade in a beater like that, or it ends up in the shed.

I've got a beater twin opt and a few choices of PT in the bone yard, smell a project.

The bias condition and reversed plate leads was interesting, never seen a rig biased so cold that oscillation wasn't audible, an extreme example of how oscillation can affect a circuit.

it didn't sound the same a dried up filter caps, after the caps were replaced.
I can see how it would confuse attempts at repair.