OT rattling on chassis

[Dyerseve726]

I have a Heyboer Bandmaster OT that is either rattling against the chassis or rattling internally. By this I mean the bass from the speaker cabinet is coupling to the chassis and vibrating the OT. It makes a pretty terrible sound. I can make the sound go away if I pull the transformer towards the back at the beginning of every session. The sound comes back after its cooled and then turned back on. Has anybody else had this happen? I'm thinking of cramming some rubber washers on the mounting screws, but I'm wondering if there's somewhere in the OT that might be rattling internally. I tightened those screws beyond reason with no change. I had to pull with a decent amount of force the first time to fix it and now it just needs a nudge, which makes me think manipulating the frame is what fixes it. I would like to sell this amp, and I'd rather not put an asterisk on the listing saying you gotta tug the OT everytime you turn it on, lol. Any other ideas? I've thought about shock absorbing feet on the amp head as well, but not sure how much difference that would make.

[uki]

Did you tight all the bolts in the transformer? Not just the ones holding it to chassis?
Rubber washers may help.

[Dyerseve726]

Did you tight all the bolts in the transformer? Not just the ones holding it to chassis?
Rubber washers may help.

There are no other bolts. It's an A-frame style.

[tubeswell]

What you might actually have is an intermittent contact on one of your input (or FX loop) jack tip switch contacts. If the switch contact is only lightly/intermittentently touching the jack tip contact (when there is no plug inserted in the jack) the loose tip switch contact will turn the chassis into a big microphone. You can test this by holding a chopstick against the input jack tip to force the tip switch to close properly, to see if that kills the vibration

[Dyerseve726]

What you might actually have is an intermittent contact on one of your input (or FX loop) jack tip switch contacts. If the switch contact is only lightly/intermittentently touching the jack tip contact (when there is no plug inserted in the jack) the loose tip switch contact will turn the chassis into a big microphone. You can test this by holding a chopstick against the input jack tip to force the tip switch to close properly, to see if that kills the vibration

The sound has no effect on what comes out the speakers. It is a physical vibration. Just nudging the OT slightly makes it go away. It's not an input issue. I can hear it rattle when I play a completely different amp sitting next to it while the one with the vibrating transformer is turned off, so I know it's nothing electrical.

[bmccowan]

Have you contacted Heyboer? They should offer some advice regardless of warranty status: https://www.heyboertransformers.com/contact.shtml

[PRR]

Does the coil rattle on the core? Does the core rattle in the frame?

Both are common loosenesses. Sometimes wood wedges are driven between coil and core. Sometimes a punch (large nail-set) is used to tighten that type frame against the core at a few places. You can go as far as gently bending-back bottom ears and side channels to get the core out of the frame, apply thin silicone caulk inside the channel (and maybe upside the coil-core gap), and reassembling.

[Dyerseve726]

Have you contacted Heyboer? They should offer some advice regardless of warranty status: https://www.heyboertransformers.com/contact.shtml

I haven't, but that's a great idea, thank you.

Does the coil rattle on the core? Does the core rattle in the frame?

Both are common loosenesses. Sometimes wood wedges are driven between coil and core. Sometimes a punch (large nail-set) is used to tighten that type frame against the core at a few places. You can go as far as gently bending-back bottom ears and side channels to get the core out of the frame, apply thin silicone caulk inside the channel (and maybe upside the coil-core gap), and reassembling.

Alright, so you're definitely telling me it could have an internal rattle, lol. I'll have to contact Heyboer and ask where they think I should look for the issue. Thanks for your input.