No SS voicing

[Tweeddeluxe1]

My mp1 has no SS output other than some white noise. I have performed factory reset, verified all levels were up. Switched a known working eprom, a known working 572n chip but still nothing. I have also replaced u2, u4, and u6 chips with pinned sockets and new chips. The tube clean and tube distortion tones are great and no other problems noted. I really want the as clean voicing. Any had a similar issue?

[MarshallJMP]

Have you tried swapping out U13(tc9176ap)?

[Tweeddeluxe1]

Yes I swapped it with the chip beside it. I still only get white noise. The volume of the white noise can be increases/decreased with adjusting the master gain and od1,od2 gains as expected. No guitar signal passes.

[MarshallJMP]

Did you check the SS enable signal?

[Tweeddeluxe1]

Would that be the voltage to r115? I measure 15.2 v on one side and 3.6v on the other side.

[Tweeddeluxe1]

I have scoped the unit to the best of my novice ability and I have a signal throughout. Could the vactrol (u3) be the culprit?

[MarshallJMP]

Would that be the voltage to r115? I measure 15.2 v on one side and 3.6v on the other side.

It should be 3.6-3.9V when you are on the tube channels and 0.08V when you are on the SS channel.

[MarshallJMP]

I have scoped the unit to the best of my novice ability and I have a signal throughout. Could the vactrol (u3) be the culprit?

Normally not U3 regulates the OD2 gain of the tube board, it has got nothing to do with the SS channel.

[Tweeddeluxe1]

Would that be the voltage to r115? I measure 15.2 v on one side and 3.6v on the other side.

It should be 3.6-3.9V when you are on the tube channels and 0.08V when you are on the SS channel.

Would that be the voltage to r115? I measure 15.2 v on one side and 3.6v on the other side.

It should be 3.6-3.9V when you are on the tube channels and 0.08V when you are on the SS channel.

I remeasured the voltage on r115 while in a SS preset. I get 0.068v

[MarshallJMP]

Ok that looks good.

Did you have signal on pin 14 of U13 when you used the scope?

[Tweeddeluxe1]

Ok that looks good.

Did you have signal on pin 14 of U13 when you used the scope?

just rechecked u13 and yes all pins have signal. New to using a scope. I'm using 0.6 volts at the input and sine wave generator.

[MarshallJMP]

Set to SS channel correct?

[Tweeddeluxe1]

Set to SS channel correct?

🤔
Now I'm unsure... will redo and get back with you asap. Thx for your assistance.

[MarshallJMP]

Ok because it has to be on SS mode else you will see signal from the tube board.

[Tweeddeluxe1]

Ok because it has to be on SS mode else you will see signal from the tube board.

seems like I need a tutorial on using the scope. So let me quickly run through my set up. I have the sine wave generator connected to the tip and sleeve of the input jack. The mp1 is on and set to preset 8 which is SS voiced. When I pin u13, the only sign wave that appears on my scope is pin 3 which I believe to be the IN. Is this set up correct?