TonePad's DynaComp - troubleshoot help

[snaper]

Hi Guys,

I've finished my first stopmbox ever. Actually, not really, but in the past I converted them into modular synth modules, etc.
My first build is a DynaComp clone from TonePad. PCB etch was easy as I'm really experienced with that thing.
The case came out really good, looks awesome.

Now, the problem is that it is not working...

My first idea was that freaky 3pdt switch, but checked again ang again, tested the connections and it is OK, the circuit has the input signal, yet, the output is still not working.
I mean, I hooked up a drum machine and active speakers to test it out, and there is some sound, but really really quiet.
I've checked the board with alligator clips, sound is coming out from the CA3080, but lost after Q2, so I replaced it, did not solve the problem, still no sounds. Replaced the 3080, still no sound...

Trimmer doesn't affect the problem.

Every part was 100% brand new.

What else should I check?

[Kipper4]

more info please

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

What are the voltages telling you?

[PRR]

And where did you get the '3080?

What is the voltage on pin 5?

[snaper]

Sorry guys about the delay, I had to buy a new meter, the other one is in my workshop, which is far away, I have only limited tools in my studio, basically for making cables.

Continuity check was done, everything seems OK, or at least should be.

Voltages :

Q1 :
E - 1,53 V
B - 1,26 V
C - 9,25 V

Q2 :
E - 2,11 V
B - 2,35 V
C - 7,08 V

Q3 :
E - 0 V
B - 0 V
C - 1,04 V

Q4 :
E - 0 V
B - 0,56 V
C - 1,05 V

Q5 :
E - 0,56 V
B - 1,04 V
C - 9,25 V

CA3080 :
pin 1 - 0 V
pin 2 - 3,86 V
pin 3 - 3,86 V
pin 4 - 0 V
pin 5 - 0,5 V
pin 6 - 2,37 V
pin 7 - 9,25 V
pin 8 - 0 V

Power voltage is stable 9,25 V from DC adapter.

CA3080 is a "new-old stock" RCA version, I got them a from a guy here in Hungary, he has a bunch, he bought for repair jobs in the past when it was "just another IC".

[snaper]

I think the problem should be around Q3/4, there are lot of 0s

[snaper]

Check all the components this morning again.
Everything is OK, everything is in the right place, orientations are also OK. Pots are OK. Switch is OK.
I have absolutely no idea...
2 things, which should not affect the build :
I used 4148 instead of 914 and I used wirewound resistors instead of metal film...

[PRR]

> 4148 instead of 914 and I used wirewound resistors instead of metal film.

Same things.

> around Q3/4, there are lot of 0s

That is actually correct for NO signal. (Did you short the input? Listen to the output while probing?) The Emitters are at zero. The bases sit near zero until a large signal stirs them up. The collectors should then sit high, over 8V. But here Q4 B is showing nearly the 0.6V ON voltage, and the collectors have fallen low, turning-off the '3080. I would look around Q4, see what is pulling the base up.

[MaxPower]

Basing this on this schematic: http://www.diystompboxes.com/smfforum/index.php?topic=93749.0

Edit: D'oh! Not the same schematic. But the question remains:


Paul, is Q1 okay? The emitter of Q1 being higher than the base (of Q1).

[PRR]

> is Q1 okay? The emitter of Q1 being higher than the base (of Q1)

Bases are sometimes biased with very large resistors. Meter loading matters then. I did not bother to see what Ra Rb are, but I'd dart 1Meg. His meter may be 1Meg, which would read half. Or 10Meg, which would read 90%.

The emitter node is less sensitive to loading. He's got 1.5V there. Less than I'd like but plenty to pass decent signal. I'm first-guessing Q1 is not the problem, but.....

[snaper]

Board looks OK.
I've measured it when there were signal, but only a drum machine, line level, not guitar.

https://preview.ibb.co/huBSw5/image1.jpg

[Slowpoke101]

I've built several of these tonepad compressors (mainly as the Dyna type) and they work well.
Having looked at your voltages and your board picture I can see a problem.

You have a short between the cathode of D2 and the emitter of Q5. On the picture this is shown near the lower left-hand corner.
Remove this short and the unit should work.

Cheers.

[thermionix]

Yep, good eye!

[snaper]

I've built several of these tonepad compressors (mainly as the Dyna type) and they work well.
Having looked at your voltages and your board picture I can see a problem.

You have a short between the cathode of D2 and the emitter of Q5. On the picture this is shown near the lower left-hand corner.
Remove this short and the unit should work.

Cheers.

Good Lord, eagle eyes!
I've double checked it, but whoa...def. will remove that bastard

[snaper]

Reflowed that bridge and now it works!
Guys, thank you very much for the help.

[thermionix]

Looks great!  I love my Dynacomp clone, also built with an NOS RCA 3080.  My favorite pedal.

[MaxPower]

Is there an alternative to the 3080?

[thermionix]

Is there an alternative to the 3080?

Yep, the CA3080A 

But seriously, there's some other OTA people use, I think it has a 5-digit number, but I don't recall.

The new manufacture Intersil 3080 sounds good too.  I'd say it's a little fatter sounding than the old RCA.  Good with a Strat.  But the RCA is the "original" sound.

[highwater]

The LM13600 and LM13700. They are a dual 3080 with linearising diodes and built-in darlington buffers.

Needless to say, the pinout is different, but if you use an adapter board they function exactly the same (the buffer and diodes can simply be ignored).

In fact, you can also make a LM13x00 out of two 3080s, four diodes and either two darlingtons or four regular transistors. (see link below)

The difference between the two is how the darlington is connected internally. If you are using them in a 3080 circuit either one will work the same.

http://www.idea2ic.com/LM13700.html

[thermionix]

Yeah 13700 is what I've seen mentioned.  I didn't know it was a dual.

[MaxPower]

Awesome! Been wanting to give this a shot. Thanks a bunch.