Marshall YJM100 schematic?

[Nyqusit5]

That's correct.

[J M Fahey]

FWIW it might be subcontracted to the same Factory that makes Bugeras, or a very similar one

[nznat2014]

hello my friend. Can you help. i have the exact same issue with my YJM100. Its identical in every way. Can you give me as much info as you can to help me fix my YJM aswell. I hope to hear from you asap. I dont want to send it into a shop as i build electronics myself, but with this amp i need a little help and its just so great to find someone with the exact same amp and situation. I hope to hear from you very shortly

thanks

jason

[nznat2014]

confirm which chip you replaced.

Got it this morning.
The Hi input is going to the boost board where it sees a 4.7MOhm SMD resistor to ground and a relay for the boos switching. But it also sees a 47nF (or 470nF) leading to the second "+" input of the 4558 used in the boost circuit. My guess is that it is used as a buffer for the control input of the gate circuit. Anyway, the 4558 was faulty giving a low impedance to ground and therefore cutting all the hi-end together with its input cap.

To be honest, this thing is not far off a Bugera as far as build quality and manufacturing methods are concerned (don't start me on the tone side, it is always very subjective). No wonder Marshall is not the hot brand it used to be.

So all you done was replace the RC4558 SMD, and it was fixed?

This is the SMD RC4558 directly on the other side of the boost dials on the rear board eh? at the far left side of the rear circuit board just under where the 2 plug sockets are eh?

thanks

[Nyqusit5]

Hi nznat2014
You got it right, this is the one I changed.

[nznat2014]

thanks for your reply. Do you have the schematic for the YJM100? I have another issue. I replaced the RC4558 and i can hear that it has worked, but i done a silly thing and while i was searching for the issue before reading your posts, i accidentially touched the end of 2 resisters on the board at the front that has the front pots, the dials for the volume, treble and so on. Can i email you while two resisters i touched so i can located what i done. After doing that, whats happening is that im getting almost no sounds at all. The speakers are humming, like the amps wanting to go, every dial on the amp is working, but there is almost no output, or like theres no input getting to the output tubes. Im trying to locate what the hell i done. there was a little short at the point i touched, or simply a tiny spark on those resisters i touched. The fuses are fine. if you email me at jason.dorne@gmail.com i can send a picture of the exact place i touched, and i really hope you can help find the issue. im sure its not much.

thanks

Jason

[Nyqusit5]

I haven't got the schematic and I don't have the amp anymore. I can't help you further I'm afraid.

Good luck with the amp