RM Octavia transistor problem

[Rethfing]

Hi, I've recently fired up RM Octavia made from tonepad: http://www.tonepad.com/getFile.asp?id=120
The problem is that I only hear sound when I hit strings really hard. From Geofex debugging page I know that this is transistor problem. I measured all the voltage's and it seems that the problem is with Q1 (2n3906). Here are all the voltages:
Q1: E-3,25  B-2,66  C-3,22
Q2: E-2,28  B-3,22  C-5,11
Q3: E-2,64  B-3,60  C-6,29
Q4: E-3,42  B-4,04  C-8,80~

I've already replaced 2n3906 with new one but the problem remains. From what I know there might be some broken part, maybe someone could point me which one it might be?

[PRR]

Re-check pin-out on Q2.

[Rethfing]

Pinout is fine. I should have mentioned that I used BC517 instead of MPSA13. I've flipped them 180 degrees because MPSA13 is E-B-C and BC517 is C-B-E

[PRR]

I hesitate to say this. My gut tells me that Q2's emitter resistor should not be same-as the collector resistor, BUT I don't recall ever noticing a typo like that in GGG's plans.

Try shunting a 3K9 (or 4K7) across the 39K which goes Q2 emitter to ground.

See if Q2 Collector comes up to 4V or 5V.

[Rethfing]

Sorry, I dont follow, where should I place this 3K9 resistor?

[PRR]

[Rethfing]

Q2: (with 3.9k added across 39k as you said Paul)
E: 0.53V
B: 1.53V
C: 2.4V

[PRR]

Does it pass sound better this way?

[Rethfing]

Hmm in fact yes, the sound passes more easily but it still doesnt react to subtle picking and sustain is really short. So what now? Lowering 39k to some value near 1k or 2k? Because we divided 39k with 3,9k resistor and its now 3,5k in total right?

[brett]

Hi
from memory, the 2 x 39k resistors are correct. It's a clever design. A similar setup is used on Q1 and the phase splitter.
The issue is almost certainly that  that you've replaced the MPSA13 (a Darlington 'double transistor') with a simple BJT (BC517).
Have fun - it's a great circuit.

[Rethfing]

Replacing transistors to MPSA13 will fix it you say?

[LucifersTrip]

No, I think both are darlington

http://www.datasheetcatalog.org/datasheet/siemens/BC517.pdf

but double check pinout...according to this, they could be the same.

http://transistor-spravochnik.ru/description/mpsa13/47355
http://transistor-spravochnik.ru/description/bc517/24671

[brett]

  Oops. Mistake about BC517. 
Multimeter with hFE will indicate the pinout easy enough. MPSA13 or BC517 will probably show 1000 (or more if meter goes higher).
cheers

[Rethfing]

Well I tried measuring HFE but my meter doesnt show any value (I guess it shows up to 1000 and its not enough). But I believe my pinout is fine, the shop where I bought them shows that it is opposite to MPSA13. Im going to order MPSA13 soon and put them in sockets