Help - Marshall clone 18w FOUND IT JTM45 or TMB18 ?

[Chupacabras]

Hey everyone,

Yesterday I bought a Marshall-style clone amp that used to belong to someone who sadly passed away. When I first tried it out, the amp worked—although the jumpered channels didn’t function, and the presence pot didn’t seem to do anything. Once I got home and spent more time testing it, I noticed it started making strange noises at higher gain settings, so I decided to open it up.

To my surprise, I found that one preamp tube was missing, and some components were not even connected. There’s also a rear input jack marked “B+” that runs to the presence pot… very strange.

I’ve been trying to find a schematic (the family has no info on the build), and so far the layout seems to be about 70% similar to the Ceriatone 18W TMB clone. The main difference is the front panel, which does not have a master volume but does have a presence pot, more like a JTM-style 18W build.

So now I’m wondering what you all would do in this situation:

Should I keep the Ceriatone TMB circuit but adapt the control layout to work like a JTM45 (e.g., wiring the presence pot as in a JTM)?

Or should I just modify the front panel, add a master volume pot, and stick with the TMB design?

Ideally, I’d like to keep the JTM-style layout if possible, but I’m open to ideas.

Also, have any of you seen a schematic that includes a rear jack labeled "B+" connected to the presence control? That one’s got me scratching my head.

Thanks in advance!

[Chupacabras]

More fotos

[Bieworm]

I think you will have to trace the signal path and write it down as a schematic to get a clearer view on what the circuit is based.

Also, the amp was formerly equipped with a CF where the unused valve socket is situated. You still see the jumper wire on it.

[Chupacabras]

Hi to everyone, i rewired all th amp as a TMB 18W and runs pretty pretty well... Sounds AMAZING. The only thing that for me is an issue is that brighter frecuencies (up to 10khz maybe) are ugly, it is possible that the V1 in the preamp has got a lot of gain??

You can see a video here (first without an overdrive pedal): https://www.facebook.com/1556533451/vid ... 611874084/