MXR dyna comp no sound with effect

[pontiacpete]

This is an original 70’s dyna comp. It is not passing signal when pressing the switch to turn on the effect. I can’t get a signal passed Q1. I have 9vdc on the cathode of the 2n5088 and can see the signal go in on the base of Q1. But there’s not signal coming out of this transistor. I had changed it to a 2n5088, there original is not being used. Anyone have an idea what I can do to get this to work? C6 has been changed and I tried another trim pot (5K was allI had) and tried another IC which I’m not sure is a good 3080. The original is back in. Thanks for any help. MXR%20M102%20dyna%20comp%20pedal%20schematic.pdf

[Helmholtz]

Here's the original schematic: DynaComp.pdf

Input transistor (Q2) is wired as an emitter follower. Collector voltage must equal battery voltage.
What are emitter voltage and base to emitter voltage (base voltage cannot be measured exactly)?

[pontiacpete]

Emitter has 0v and base to emitter has .070vdc

[Helmholtz]

Emit has 0v and base to emitter has .070vdc

The base is biased via a 1M resistor (R5 according to original schematic). What is the voltage at the other end of that resistor (node between R2 and R17)?
Should be around 3V.

If that voltage is good, either the transistor is bad (check with meter) or more likely it's not correctly inserted according to its pinout (see datasheet).
What happened to the original transistor?

(As always, could also be a broken trace or bad solder joint.)

[pontiacpete]

there’s 2.98vdc on that side of R5, between R2 and 17. .080v or so on the base side.. The original might be gone. I was holding on to it but now I can’t find it. I might try the garbage can next. So the 2n5088 facing the flat side of the transistor I have the right leg attached to 9 battery connector, so I’m thinking that’s correct.

[Helmholtz]

Did you test the transistor?

Your voltage measurements show that there's no emitter current (actually no wonder as there's no base bias).
So assuming transistor leads are correct, either the bias through R5 doesn't reach the base or there's a base to emitter short.

Ok, do measure base voltage. Reading will too low because of meter resistance, but need to see if there's a positive voltage at all.

[pontiacpete]

How much voltage should I be seeing on the base of Q2? 3vdc thru a 1meg resistor ?
There is no short between E-B, for sure. I even changed the transistor to a 3904, the same voltages.

[Helmholtz]

How much voltage should I be seeing on the base of Q2? 3vdc thru a 1meg resistor ?

The base current causes some voltage drop across the 1M resistor and there's some loading by the meter, so base voltage should be lower than 3V.
My notes from around 1980 show a base voltage reading of 2.0V.

Are you really sure you don't have collector and emitter leads reversed?

[pontiacpete]

That must be it. Even though I’ve been repeatedly checking the pin out there, I going to reverse them.

[Helmholtz]

Success?

[The Dude]

Look up the datasheet for whichever transistor you are using and match pinout to the schematic.

[pontiacpete]

I put the 2n3904 in backwards and there was 1.4vdc on the base but nothing on emitter and no signal. I put it back the way I think is correct. Maybe someone might see my mistake. I hope.
The 470K resistor to the right top of the trim pot is where the collector of Q2 and the red wire from the battery connector are connected together.

[The Dude]

The transistor looks to be installed correctly in your picture.

[Helmholtz]

What resistance do you measure from emitter to ground?

[pontiacpete]

Emitter to ground is 10K