Memory Man Solid State Echo Chorus (No Effect)

[Champagneperfume]

I apologize if this isn't the correct place to post.

A friend of mine randomly found one of these in a give-a-way box and asked if I could help.

The pedal works in bypass, but when engaged, the unity gain drops a bit and there is no modulation whatsoever. Any idea as to where to start? Obviously an audio probe is my first thought but since it seems to operate at a higher voltage, I don't wanna shock myself lol.

 

[swelchy]

someone else has been in there doing some dodgy wiring for sure

 

[jwin615]

They may have messed with the trimmers as well, but that burnt mess around them may be EHX NYC original also.
I'd take a good look at the caps in the power supply and the output voltages first. Very likely needs a recap since it runs on mains, not LV DC. Then try the trimmers.

 

[Gordo]

In old EHX boxes it's hard to tell dodgy repairs from the original factory wiring although painters/duct tape is a bit of a giveaway. Would be cool to get this old beast up and running again.

 

[Stickman393]

Looks like you got a step-down transformer in there. It also looks like the connections are all well insulated - you likely don't have any exposed 115vac hot bare connections in there. That said - safety first. Measure and check.

Id measure for AC voltage across the points where the red wires connect to the board to see what you're dealing with. They probably rectify the low voltage AC on the board. An original schematic would be a godsend here.

Edit- got it covered here.

Looks like the transformer taps should be roughly 15vac - 0vac - 15vac.

Schematic:

Once you confirm AC voltage, you'll need to determine proper DC supply. That NE5554N is going to regulate +15vdc to ground on pin 14 and a -15vdc to ground on pin 11. Input should be pins 1 (>+15vdc) and pin 4 (<-15vdc).

No AC? somethings up with the transformer. AC, but no input DC? Take a look at the bridge rectifier, filtering caps (the big 470uF guys on the opposite side of the board), and associated components before your NE5554N bipolar voltage regulator. Input DC, but no output DC? The ne5554n is likely toast.

Those are out of production, though the ne5554n's datasheet directly references the 79 and 78 line of fixed voltage regulators as work-alikes. If it's busted, it's job could easily be done by a 7915 and a 7815. Just bipolar voltage regulation, nuthin fancy.

The good news is that this is pretty simple for a memory man. You won't get a ton of delay time out of it, but it should certainly be repairable. Even the BBD is easily obtained these days.