JMF (Dean Markley) Spectra 225

[Danglin' Fury]

Does anyone have said schematic? I currently have one on the bench and have repaired the foot switch so it changes channels, combines them, turns distortion on and off and turns chorus on and off. Buuuuut it will NOT turn the reverb off. It is stuck on. That's a good thing, I suppose, until the customer wants to use the foot switch to turn it off. Lol! Hence needing said schematic. Thanks for looking!

[Steve L]

Here you go,
Steve

JMF Spectra 180, 200, 225, 410 Power Amp Schematic.pdf
JMF Spectra 210, 225, 410 Preamp Schematic.pdf

[Danglin' Fury]

Holy sheep shite, Batman!!! Thank you sooooo much!

[Danglin' Fury]

Do you happen to know what IC is responsible for the switching? Is it the CD4011BE? I believe that is a NAND gate IC.

[g1]

It looks like the #6 of the footswitch jack goes to a Fet that turns off the reverb.

[Danglin' Fury]

Ok. Yeah I see that! Thanks man! I just can't read the fet number or type. I'm using my multi-meter and I'm trying to read some continuity between the reverb switch and ANY of the fets in this thing and I'm not getting it. Lol! That's probably the issue. Lol! I'm getting continuity between the actual switch on the foot switch and the connector in the amp, then from said connector in the amp to the preamp board, but nothing after that. The reverb works and sounds ok, but I just can't shut it off. Maybe there is a trace broken or some seriously cold solder goin on. Hmmmmm...

[g1]

There is a resistor in series between that line #6 and the Fet. There is also a resistor from the (-) supply to that #6 line. So you should measure a (-) voltage on that line when reverb switch open, and 0V on that line when reverb switch closed.