No input front or rear MP-1

[MarshallJMP]

My guess is that that jack is busted,so i would suggest putting the jack mod in there.See pic for connections.

[Mxzx]

Ok will do and report back.

Thanks

[Mxzx]

Did the swap, still nothing on the input.

When I plug in headphones, and turn level all the while up, I can tap on components and hear it in headphones.  It appears I have tons of output, just no input.

What should I do next?

Thanks

[MarshallJMP]

Do this again and let me know,both front and rear input.

Plug in a guitar cable and measure with an ohm meter on the other end between tip and sleeve,you should have around 1 M ohm of resistance.

[Mxzx]

Yes, I have 1M on the guitar cable, both inputs.

[Mxzx]

Anyone have any more guidance on where I might go from here?

Thanks

[MarshallJMP]

Ok measure again between point 1 , 4 and 2 , 3 again should be 0 ohms regardless if something is plugged in or not.

[Mxzx]

Yes, just checked and that is what I read on those terminals.

Thanks

[MarshallJMP]

Ok,do you have or know someone with a scoope?

[Mxzx]

No I don't have access to one.

[MarshallJMP]

Mmmm it will be very difficult without one.Now sometimes this could be a U4 (opamp OPA2604AP) problem.You could try to check if all the connections are in order.Compare them to the schematic.Most importent are the voltages + and -15V (pin 4 and 8),pin 3 should be grounded so measure between pin 3,4 and pin 3,8 there you should have +15V and -15V,pin 2 should be connected to R83 and pin 1 to C31.

[Mxzx]

Ok thanks. Il do some digging and see what I can find.

I got a bag of old parts with it, and it looks like quite a few of the opamps were changed.

[Mxzx]

Can you point out on the board where U4 is and the res/cap?

Thanks

[gtmm]

Mxzx,

I'm attaching two jpgs to this. The first one shows where U4 is -- from the perspective of taking off the top and looking down, with the front panel facing you.  U4 has a red rectangle around it.

The second jpg is the schematic showing U4, with a red polygon around it.  :crazy:

Good luck, I hope you get it working; they do sound nice.

[gtmm]

Mxzx,

U4 seems to be a non-inverting voltage follower. There appears to be no resistors or caps in U4's circuit and exists only to buffer the input jack and is a NE5532 (I think, the schematics are hard to read at times). Marshall will have more to offer, as he knows this stuff much better than myself.