Orange AD30TC - Weird "Ghost Notes"

[earache]

Howdy

I have an Orange AD30TC combo that is making some weird sounds when tapped or struck...kinda like a static/sizzle sound. Sometimes I can hear it on top of the notes when playing, and occasionally I can hear whistle/squeal sounds that start and stop intermittently when the amp is on.

I have had the main circuit board out of this amp (no small task, lotsa wires running over the board...) and have run a hot iron over all solder points. Even after that, when I tap the main circuit board I get that static/sizzle sound, or also when I tap any tube (all tube sockets are soldered to the main board). I have sprayed and retensioned all tube sockets - twice.

I have the schematics for the main board and have tested all of the DC voltages. They are all about 5% low, but are consistent.

Anyone have similar experiences with an amp? Is it a question of me not finding the bad solder joint or component...or could it be that the filter caps need to be changed?

OrangeAD30TC Main Board P1.pdf

OrangeAD30TC Main Board P2.pdf

Thanks In Advance!

[Jazz P Bass]

Try replacing the preamp tubes one at a time.

It sounds like you have a microphonic tube.

[J M Fahey]

Tap all tubes one by one with a Bic pen to see if one of them is much louder than others and is *clearly* microphonic.
Scratch along the glass for a more precise detection.

Also tap one by one all parts trying to find the same.

Then tap one by one all pots (knob and body), jacks and switches.

If " all make the same noise" then microphonics is somewhere else in that chassis and reacts to general vibrations, when you find the actual microphonic part you will have no doubt about it.

Also tap one by one all the solder joints.

Also tapping on the same place, move all controls and check which one affects the noise.

Incredibly boring and unimaginative checking, but so thorough that it can not escape.

Do not replace parts until you find the noise source or you might have pulled or repaired it by sheer chance and you'll waste weeks chasing ghosts.

[TimmyP1955]

I usually find that Murphy is not on my side. Case in point yesterday - it did not matter where I tapped or which tube I flicked the top of. Had to swap tubes to find the bugger.

[52 Bill]

...it did not matter where I tapped or which tube I flicked the top of. Had to swap tubes to find the bugger.

Sometimes it works better to use a rag to muffle the tubes one by one, while tapping on the chassis and other tubes.

I use one of those silicon tube puller sleeves.

[TimmyP1955]

Sometimes it works better to use a rag to muffle the tubes one by one, while tapping on the chassis and other tubes.

I use one of those silicon tube puller sleeves.

I'm never so lucky as to have that help ;-(