Tychobrahe Octavia not working

[ward]

Hi,

I'm havin' trouble getting my Tychobrahe octavia going.

If anybody would be so kind to read what I did
and comment on what I'm doing wrong.
That would be very kind.

I used the pcb from GGG.
The version with the negative ground supply

Parts substituted:
Q1 = 2N3906
Q2,Q3  = 2N3904
R7 was changed by 1K2ohm
The transfo is different:
prim. impedance 20k
sec. imp. 1k
(I put in what I could find in my local electronicshop)
diodes are 1N60

Q1:   E: 6,2      
   B:5
   C: 1,52
Q2:   E: 0,92
   B:1,5
   C: 9
Q3:   E:0,3
   B:0,9
   C:8,38

Almost all voltages are way off, compared to the voltages at GGG.
But it seems to me that Q2 and Q3 could be working.  Please correct me if I'm wrong

I checked the traces for continuity and for shorts.

I cut out C2, C3 and R1,
then I measured ...

Q1:   E:6,6
   B:6
   C:6,5
?
When I take out the transistor, the voltage between R2 and R3 is 3,5V.  And that's what it should be ...



Thanks

[brett]

Hi.
Yes, as you had partly diagnosed, Q1 was a problem.
A universal rule is that any working resistor has 0.6V difference between the base and the emitter. For PNP the emitter is 0.6V higher, and for NPN it is 0.6V lower.
A 2N3906 is a good choice for Q1.  Check the wiring around it, then try another one.
good luck

[ward]

What do you guys think of the transformer.
I don't see a reason why it shouldn't work
whether it'll sound OK that's something completely different.

[brett]

Hi.
Your primary to secondary impedance ratio is 20:1, while the schematic calls for 3:1.
Look for another that's closer to 3:1, or if that's not possible, make sure that you connect the high impedance side to the diodes.
cheers

[ward]

Thanks for the replys Brett,
I got the tychobrahe working after laying it aside for a few days.

I had all my transisors reversed ... classic mistake I assume.
A bit stupid, but what's more important,
it works and sounds good.
Much better than the roger mayer octafuzz I made.

[SG Lou]

Funny that i came across this thread. I built the same one Ward built. I finished it,, plugged it in and it sounded fantastic from the word Go.
Now it doesn't work at all. I don't have the foggiest idea even where to begin to look.