Ross compressor debug

[quackounet]

Hello,

I usualy find my answer with the search, i debuged other projet with it, but this time i need your help please.

I build a Ross compressor, with the mod i found on fuzzcentral (exept the switch with the resistor, i have a 150K there)

My build when gain to max only have a very little compression(almost none), i saw in other post that you can have a little distortion with high outup pickup (it's what i use, but for me it don't happen).

I checked voltage as explained on fuzzcentral, but i really can't see where something is wrong, so i'll post them.

I used 2n3904 and IC is a LM13700

Q1 C:7.62 B:1.33 E:1.55
Q2 C:6.98 B:2.44 E:2.20
Q3 C:8.04 B:0 E:0
Q4 C:8.04 B:0 E:0
Q5 C:9.25 B:8.05 E:8.65  (Q5 B is 8.73 when probing but decreasing quickly to 8.05)

IC
1 : Amp bias input : 1.13
3 : Input + :3.97
4 : Input - :3.97
5 : Output : 2.44
11 : V+ :9.25
6 : V- :0

(I used stripboard and it's with a millenium 2 bypass)

Thank you, maybe there is nothing here and i was expecting too much from it...

[quackounet]

I'm still trying to debug it by myself, since i have not much knowledge in electronics(only know some basics) i don't know if i'm right in my reasoning.
If someone can correct my analysis it'll help me to learn more how to debug

I think that all my input are little low in voltage, no ?,

Q1 base lesser than the emiter ?
i guess i should try to resolder everything from Vb.

Q2 seem ok, (lower but since Q1 don't work as intended)

Q3 and Q4 collectors should have 9.25 no ? like Q5 collector

Q5 base decreasing to 8.05 is that it's supposed to be ? or else how it can happen ?

And try by removing the millenium board (if i made a mistake on it, it can effect the effet board ??)

If someone has another suggestion where i should start looking don't hesitate

[duck_arse]

definately your q1 emitter is to high for your q1 base voltage. I don't know that the lm13700 is compatible with this circuit as is, it has the q2 buffer transistor built in, and is a dual, isn't it? q3 and 4 look wrong too, but I can't lay my hands on my annoted circuit, and I can't do transistor voltages in my head like the experts, who may be along any minute now.

now I've looked again, q3 and 4 will be b and e 0V, because there is no sign of any dc on their bases, no?

[quackounet]

Thank you, i checked with the value here http://fuzzcentral.ssguitar.com/ross.php

and i just found a schematics with the lm13700 i'll check it tonight at home, http://www.rockcreekband.com/projects/index.htm

[PRR]

> Q1 base lesser than the emiter ?

Probably correct. Depends on your meter.

Emitter at 1.5V is not wrong.

The Base is a HIGH impedance point, 940K, thus subject to meter loading.

(Similar issue at OTA Out.)

If E is at 1.55V, we expect B at around 2.15V. You found it at 1.33V, or 0.82V low. A 0.82V drop in 940K is 0.87uA. This suggests the meter draws 1.33V and 0.87uA. 1.33V/0.87uA is 1.52 MegOhms.

So is your meter rated 1.5Meg input?

That's an odd number (10Meg is traditional), but some Flukes are 1.5Meg.

Anyway, to prove yourself that this "1.33V" is meter loading, get another meter (can be cheap). Watch Q1 Emitter while you poke the Base with your first meter.

[quackounet]

oh i see, thank you, i didn't know this

it's was cheap one, i'll see if i can find another one to try.

And just found out my battery is at 8.85v today and was at 9.25v when checked the voltage, didn't do anything between...(it was removed)

I'll check again with a new battery , or a dc adaptator.... If that resolve the problem i had, i think i can hide and change name....