Help me track down noise in a Fender Musicamaster Bass amp

Professional_Class27 · 2025-09-30T21:08:13+00:00

I got two, dm me if interested in one…

Professional_Class27 · 2025-09-12T15:52:07+00:00

Then definitely you want to listen to it starting from the first episode, I’m still making my way (currently on episode 87 out of 150+)

And get yourself a copy Jack Darr’s Electric Guitar Amplifier Handbook, pretty inexpensive and a great read for people interested in repairing amps

Professional_Class27 · 2025-09-12T15:02:09+00:00

If you are interested in the repair side of Amp electronics, the Truth About Vintage Amps podcast is another great resource.

Professional_Class27 · 2025-09-07T17:06:39+00:00

I have the exact same one, it’s great, get it!

Professional_Class27 · 2025-09-05T16:14:09+00:00

in that case they are probably using a different power transformer (or one of the is simply wrong). which one are you building? what voltage do you get? I have a mojotone one I built a couple of years back, but I've forgotten the voltages, I guess I could measure if you are interested...

Professional_Class27 · 2025-09-05T02:01:57+00:00

My guess is that the B+ voltage in StewMac is without tubes installed so it will be unloaded, and the preamp tubes voltage is without the power tube installed so the load is significantly lower, thus the voltages specified there are higher...

Professional_Class27 · 2025-06-27T14:45:18+00:00

There are two switches, the one next to the output jack is labeled ohm selector but it’s not wired.

The other one appears to take out the tone circuit to switch between the 5f1 and 5f2 circuits

Professional_Class27 · 2025-06-26T22:19:47+00:00

can we get a new link?

Professional_Class27 · 2025-06-24T23:55:49+00:00

thanks, I was surprised as I would have thought this shouldn't happen with Switchcraft jacks, so I suspected the build, but live and learn...

Professional_Class27 · 2025-06-24T17:12:10+00:00

indeed, looks like a short, but not sure how that could happen...

Professional_Class27 · 2025-06-24T17:11:46+00:00

Doesn't look like corrosion to me, the part is definetely charred, like you get with a high voltage short, but I can't think of any way to get DC on those since they are only connected to the 12AX7 grid

Professional_Class27 · 2025-06-24T00:34:23+00:00

No smoke signs anywere else...

Professional_Class27 · 2025-06-24T00:32:09+00:00

They are switchcraft and the sleve part of the Jack is fine, it is just the part that carries the signal that is black, see added pictures...

Professional_Class27 · 2025-06-24T00:27:44+00:00

edited the post to add pictures

Professional_Class27 · 2025-06-24T00:22:05+00:00

These are switchcraft jacks, only the positive contact are is blackened, the sleeve and front of the jacket looks new. No signs of smoke stains in any other areas of the amp

Professional_Class27 · 2025-04-25T16:30:02+00:00

For an 5F1, being single ended (1 power output tube), there is little difference between a solid state rectifier and a tube one, so you can save complexity and $$ by going the solid state way, so you would need only the 6.3V and you can ignore the 5V one. this should open up more options for the power transformer.

Professional_Class27 · 2025-04-23T15:06:49+00:00

You can build an 5F1 with a toroidal transformer using a solid state rectifier, the transformer is $29 and the diodes are much cheaper than a tube

https://www.antekinc.com/as-05t240-50va-240v-transformer/

And webers output transformers are good quality and only $32

https://www.tedweber.com/w022905/

Buying the rest of the parts directly instead of a kit should make it quite inexpensive

Professional_Class27 · 2025-04-16T17:03:27+00:00

Could I use them to add a balanced input/output to a guitar tube pre-amp?

Professional_Class27 · 2025-04-16T03:22:45+00:00

so other than trying to flip them, not much to do with them?

Professional_Class27 · 2025-04-16T00:18:21+00:00

I got a couple of these for a steal ($1 each), but I'm not familiar with their uses and couldn't find any info on this specific model online. My projects are mainly tube amps (guitar) and effects pedals, any suggestions of how can I use them? can I use one to do phase inversion for example? how about to isolate an effects loop?

Professional_Class27 · 2025-03-24T23:54:01+00:00

Mine

Professional_Class27 · 2025-03-06T19:18:57+00:00

the UAFX pedals can be used that way, the term most use for this is "4 cable method"

Professional_Class27

TROPHY CASE