re-capped fender twin silverface and modded to blackface

[rp]

If an amp’s been kept in a Seattle carport for years and then goes to Arizona to for a while why doesn’t the board dry out, and why doesn’t the hair drier trick work well? Does moisture permanently alter the board making it forever conductive? Some form of corrosion or oxidation of whatever is mixed into the fiberboard?

My bonehead story about flux remover spray: I’m at the kitchen sink spraying a board clean (tiny NYC apt folks). I got the windows wide open for all the obvious reasons. My stove is some 5 feet down from the sink along the countertop. I got a kettle on for tea, that I’d completely forgotten about as I usually do with kettles and tea. As I’m spraying abundantly away I spy from the corner of my little eye a low slightly quavering flow of gas, like a liquid wave, intently creeping down the counter towards the stove. Time slows to dead crawl, in a bare second that seems like minutes I watch the low wave of flux spray reach and touch the burner flame. I actually see the wave light and like a fuse come back towards me. I’m aware I’m standing over a basin full of heavy highly flammable flux remover spray and POOF-engulfing-FLASH. From observation to synthesis to consequence all over in a super micro mini nano second. So, I’m still in place, damn spray can and board in hand, singed hair smell in the air. I run over to a mirror expecting to see Wile E. Coyote after an Acme rocket mishap - or much worse, but I’m fine, can’t find any hairs out of place. I take a deep breath and look over myself more carefully, still fine, kitchen’s fine too. I’m seriously stoked over my big dumb luck, and still am years later when I think about it. I'd survived a Richard Pryor moment. Needless to say, I put everything away including the damn tea, cleaned up, went out for breakfast and a happy morning walk, had a few beers, and did absolutely fuck-all nothing for the rest of the day.

Anyway, I know I’m a knucklehead, but I did open the all the windows. Which I found doesn’t really matter. Apparently flux remover is like ether, it is heavy and likes to fall and hold together rather than diffuse quickly up into the air. The wave moving along the counter was a gas but it was moving like a liquid. So be extra careful, even a cigarette in an ashtray far across a garage would freak me now.

[Curranproducer]

I feel like I should really redo the entire damn board. if that is the consensus on why it would be motor-boating.

[pops]

I would do a new board if it is that bad.

[Richie]

I feel like I should really redo the entire damn board. if that is the consensus on why it would be motor-boating.

Seems a lot has been changed or replaced. Its always good when doing a bunch of changes, to do them one step at a time. Check and recheck. Then move on to the other changes.

So this motorboating. Does it happen in both channels? Turn all tone controls down Both channels. Start with the normal channel first. Then bring up the level of the controls on that channel. See if that channel motor boats. If not move to the Second channel, and try the same there.

You could have a new bad component or cap. The new mica's can be leaky. Try to narrow it down to the section. I think someone posted, you could pull one preamp tube to see if it effected the motorboating.
Many things can cause that. I would think it would be more of something you changed, if it wasn't having this problem before the changes were made.

Yeah if the board had green mold on the parts, then you could have used a brush with denatured alcohol to clean it up some. Did you have some pics of the chassis? Sometimes when replacing or making lots of changes, you can put something in the wrong spot. Amp may work, just not work like it should.

[Baxtercat]

If an amp’s been kept in a Seattle carport for years and then goes to Arizona to for a while why doesn’t the board dry out, and why doesn’t the hair drier trick work well? Does moisture permanently alter the board making it forever conductive? Some form of corrosion or oxidation of whatever is mixed into the fiberboard?

After drying, plenty boards I've seen have what looks like rust stains around the trem bug or mounting screws.

Good Slo-Mo story!

[Curranproducer]

the motor boating has only happened on the vibrato channel but only after it has been played through. it doesn't just happen when you peg the volume. I will go through both channels and see what happens

[Curranproducer]

so I slipped the new fiber board in between the old fiber board in the circuit card and I have everything pegged to 10 on both the normal and the vibrato channel the motorboating sound can be controlled by turning the bass control down depending on which channel I am in I get motor boating on both channels but I can stop it from motorboating by turning down the bass control for whichever channel I am plugged into