Help debug a Roger Mayer Octavia

[carrejans]

My Roger Mayer Octavia isn't working. Bypass = OK. Led = OK. Sound = zero.
Here is the layout I'm using (haven't made any part substitutions or modifications):





I doublechecked all the connections; and looked for solder bridges. Didn't find any mistake, now.


I then checked with my multi-meter. Here are my results:

BATT
8V

Q1
E = 3.4V
B = 3.4V
C = 2.8V

Q2
E = 1.98V
B = 2.84V
C = 4.78V

Q3
E = 2.3V
B = 2.78V
C = 5.6V

Q4
E = 2.99V
B = 1.9V
C = 8V

D1
A = 0.7V
C = 0.4V

D2
A = 0.7V
C = 0.4V


I hope you guys can help me. Thank you!!

[Pedal love]

The layout doesn't show which type of transistors to use. Did you use these or equivalent? : Q1 2N3906, Q2-Q4 MPSA 13.

[oskar]

Q1
E = 3.4V
B = 3.4V
C = 2.8V

Q1 emitter/base shorted?

Audioprobe...

[carrejans]

The layout doesn't show which type of transistors to use. Did you use these or equivalent? : Q1 2N3906, Q2-Q4 MPSA 13.

I used exactly those!

[carrejans]

Q1
E = 3.4V
B = 3.4V
C = 2.8V

Q1 emitter/base shorted?

Audioprobe...

No short!

[carrejans]

Any other suggestions, where something can be wrong?

Thank you.

[carrejans]

This one's driving me crazy.
I doublechecked everything. All the transitors are placed correct, all the caps too.
I closely checked all the solder points; no bridges.

Can you see something wrong at my measurements. Something that looks suspicious.

I also made an audio probe like you guys said. But it's not helping much.
Are there certain points, that I should definitely check?
-> I noticed that at the base of the first transistor my volume is dropped a lot. Is this normal?

thanks...

[Pedal love]

Tell me where your two diodes off the phase splitter section are going/coming from? Don't worry about what the layout shows, just describe what you have right now at the two diodes.

[Pedal love]

Its just that this layout is hard to follow. I can't. Right here, there is the anode of one diode seeming to go into the same trace the cathode is connected to.


Please check all of your connections against a correct schematic and post your findings, back here. Thanks, Terence.

[carrejans]

Yes, the layout is not always easy to follow.
I use a board made by John Lyons; I assume he has drilled it correctly. 

The cathodes of both diodes are connected together, and going to the 100k resistor.
The anode of the one above is going to the cap.
The anode of the lower one is going to the 820k resistor.

That's correct, I assume?

[Pedal love]

Yes its two parallel paths coming from the phase splitter, having two 22uf electrolytic capacitors connected to the emitter on the bottom and collector on the top, with 2.2m and 820k in the parallel paths with the capacitors and as you say, they both go to the 100k resistor and couplimg to the next stage with a  cap/pot/cap

Jan- is there anyway you can take a picture, I or somebody can get a better idea. Its just too hard unfortunately, to break this down verbally. Thank You.

[carrejans]

I don't have a camera at the moment. But I have a crappy camcorder. 

I just made a small clip, with really bad filming, sound, ...
Maybe it helps a littel? I don't think so. 

I did some testing with audio probe. As you can hear, very little sound at some spots.
Maybe there are some important spots, I should test?


http://www.youtube.com/watch?v=Qs2X39i8PEI

[Pedal love]

Have you noticed that the voltage on your base and emitter on q1 are the same. That seems to be a bit odd. I can't make anything out from the video. Cut and paste the sticky from here on DEBUGGING-what to do when it doesn't work. A lot of us could seriously fix it Jan, but we haven't the advantage of being there. The best that could be done here is lead you in the right direction, so you can do it yourself. Terence.

[carrejans]

Ok here is my measured data, like on the debugging-thread:


1.What does it do, not do, and sound like? -> no sound at all
2.Name of the circuit = Roger Mayer Octavia
3.Source of the circuit (URL of schematic or project) = look few posts above
4.Any modifications to the circuit? No
5.Any parts substitutions? No
6.Positive ground to negative ground conversion? No
7.What is the out of circuit battery voltage? => 8.58V
Voltage at the circuit board end of the red battery lead = 8.54V
Voltage at the circuit board end of the black battery lead = 0V



Q1
C = 3.0
B = 3.6
E = 3.6

Q2
C= 5.0
B= 3.0
E= 2.13

Q3
C= 5.9
B= 2.9
E= 2.5

Q4
C= 8.5
B= 2.0
E= 3.2

D1
A = 0.7V
C = 0.4V

D2
A = 0.7V
C = 0.4V

[Pedal love]

Well I'll tell you Q4's base should be about 4.25v, considering the supply voltage is 8.5v. Check this section and post results.

[carrejans]

Did some more measurements.



the point with the $-sign: at first I measure 7.3V, than it drops to 6.7V. Don't know if this is normal

[carrejans]

I realised I haven't posted a schematic.
Here it is:

[carrejans]

Well I'll tell you Q4's base should be about 4.25v, considering the supply voltage is 8.5v. Check this section and post results.

Yes, I see now, that it's a voltage devider; should be the half of 8.5.
Will check this out.

[carrejans]

Well I'll tell you Q4's base should be about 4.25v, considering the supply voltage is 8.5v. Check this section and post results.

Yes, I see now, that it's a voltage devider; should be the half of 8.5.
Will check this out.

Everything looks connected and soldered ok in this area. Don't get it...

[Pedal love]

What I really feel is in these circuits normally the collector has the highest voltage and then base and emitter. Your base shows 2.0v then your emitter 3.2v, funny since .6volts is burned forward biasing base/emitter on q4. That makes emitter -.6volts than base.