Feedback on my JMP 50W Bass head (1971)

[leadandbass]

Hello everyone, I am very grateful for any feedback on pictures of this JMP 50W bass head.

Currently, it does not work as the output transformer is broken. Can anyone point me towards the most authentic replacement?

Many thanks!

 

[fusedbrain]

This one is probably your best bet.
I've used it in a couple of builds and it sounds great. It's a replica of what's in your amp and is readily available.
https://store.metropoulos.net/collectio ... ke-784-139
Chris Merrin also makes well regarded Marshall repro transformers, but he can be difficult to deal with / get a hold of.
If you are on a budget, these sound great as well, but not sure how much it exactly replicates what's in your amp.
http://store.triodestore.com/outrformajcm.html

Are you sure the OPT in your amp is toast though. How did you test it ?
edit: just realised this is a different amp from the one you posted yesterday. This one has had some work done on it.
At the very least, check the large white screen resistors on the tube sockets.

 

[311boogieman]

Hello everyone, I am very grateful for any feedback on pictures of this JMP 50W bass head.

Currently, it does not work as the output transformer is broken. Can anyone point me towards the most authentic replacement?

Many thanks!

What is your budget and are you planning to do the work yourself? How do you know it is the OT? Not questioning you, just curious.

Classic Tone is probably your least path of resistance (no pun intended) and there will be debate among the smart people here as to what is your best 'Authentic' option may be. Heyboer or Metro may be another one.

Also, if you put a lower case 'L' at the end of the imgur code it will reduce the size of your photos - if you need that ever.

Good luck,


Edit: Listen to fusebrain

 

[leadandbass]

Thanks for the imgur tip! The problem started during a recent recording session where there was suddenly a strong smell of burning "plastic" and subsequent smoke from the amp before it cut out. I took it to a local tech who (as far as I understand, because I live in Spain and my Spanish is limited) diagnosed a failed OT. Intuitively, I thought it would be the power transformer. I am going to call him again tomorrow to make sure. I can see a white capacitor on what I believe is the output that looks new. I will check the screen resistors as advised by fusebrain.

really appreciate the input. nice forum.