FWIW: Switchcraft makes isolation washers for their jacks.

https://www.tubedepot.com/products/isolation-washers-for-1-4-input-jack-flat-shoulder?srsltid=AfmBOopLRJix5gkjMcz9KdZDMnK0ud8XFPIuZlIIjxTb4ncYBa4kMdX6

I de-ciphered and re-typed the list as best as I could and added a few more.

Also here is a list of PC Boards while I'm here.

This is an old photocopy from my file cabinet. Bad copy but better than nothing I guess.

Do you have any DC at pin 1 of U5 ? 
Schematic attached.

As far as I know that is the Acoustic number for the 40410.  If you search for that number you will find a lot of posts about different subs people have used. 
The issues are finding something with the same pinout that will physically fit and have a heatsink. 
If you can find a 2N5679, that should be able to work if you reuse the existing heatsink.  Seems like Mouser has stock on them.
Otherwise, something in a TO-126 package can be made to work with the existing heatsink.

I'm trying to fix an Ampeg BA115HP which works in all respects apart from having a hum with no signal at input. The hum is caused by a 0.35V DC at the speaker.

The amp has 4 power mosfets and the unwanted DC is where all the drains are tied together. The bias readings are all correct (between 15-20mV across each 0.33ohm 10W between source and rail for each misfit).

Any suggestions for please for how to eliminate this DC? Is it a case of making sure all the mosfets are a matched quad?

Thanks for any help.

Is this one of those transistors that looks like a TO-5 welded to a small heatsink ?

https://www.ebay.com/itm/364778815801?_skw=40409+transistor&itmmeta=01JT2DBRD9SAA9TZ9G682QKNNS&hash=item54ee830139:g:qXsAAOSwxj5l7SZo&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1ebO2I4P7B0y9cqe%2FLpuc%2Bcnd4BcCLtZN5aDO3gCTpR4j2Ux3uXDH%2FqkdI41qdvCdP7JuQwV7hz%2F1EnMO%2FJzzCaRnfkXHRkL1eRogNyyy3RDCu8EnNiZ3eK502CevyOHC6OLfQMxihEPEFIFiH9gAuzevo4y5AsbW%2FlRe9ZSgTfo0QHfFea29kNXL4m7n2NTNK9avTWxRByjIPHnmdu4%2FIjO5yJ6u4FCDPBPxezVT8ggb35hV1igphYxuPOTY0iE--sLBXmHuTQa9R%2Fjnm88p%2FOaxLeXtlppPy2WdJ2%2FSsg7g%3D%3D%7Ctkp%3ABk9SR96Gr83QZQ

Acoustic 470 or 450?

Quote from: J M Fahey on April 29, 2025, 04:09:26 PMBoth jacks shown are wrong for thatb use.
To boot they are *wired* wrong.
Also external speaker jack must disconnect internal speaker when used, amp can not drive two speakers at once.
Too busy now but tonight will upload proper jack and wiring.

both jacks are supposed to disconnect the internal speaker when a 1/4" plug is inserted into the jack. I never intended to drive more than one speaker. I agree that neither switch is insulated.  Nor will I argue that I may have wired these incorrectly. I look forward to seeing your solution!


thanks,

Tom.

Quote from: g1 on April 29, 2025, 03:02:13 PMAlso, the noise you experienced must be due to the dress of the wires.  Where you routed it through the back of the chassis must be a sensitive area.

Usng a metallic uninsulated jack bolted to chassis shorts a great part of NFB , increases gain big time and makes "natural" noise unbearable.


Solution is usin g a properly insulated jack, properly wired.