HEEEELP - Tonepad's Maestro FSH don't work!

[gigimarga]

HEEEEEELP again please!!!

[oldrocker]

I don't know if this is significant but I copied this out of chipcatalog.com.  So I would think that a LM13700 should work better but I thought that the circuit may have a reason for using a LM13600

The output buffers of the LM13700 differ from those of the LM13600 in that their input bias currents (and hence their output DC levels) are independent of IABC. This may result in performance superior to that of the LM13600 in audio applications.

[gigimarga]

Thx oldreocker...in a couple of build reports on tonepad is written that it works with LM13600, in some is written that it works with LM13700...

Anyway, I HATE THIS CIRCUIT FROM THE BOTTOM OF MY SOUL

[Eb7+9]

here's a few things you can try :

take a pot wired between rails and tie the sweeper to the Gate of the second (source follower) jFET and see if that controls the filter at some point in the sweep ... you can't damage the OTA's if the 22k protection resistors are in circuit ...

attach an LED in series with a 4k7 resistor between the output of the clock op-amp and ground ... this will show if your LFO is working ...

if your LFO shows sign of life and the filter reacts to voltage applied to the Gate of the sceond jFET then do the potentiometer trick on the input of the sampling channel ... remove or open the connection to the noise source op-amp to the Drain of the first jEFT and provide voltage to the input of the channel via the pot sweeper ... if that doesn't work but the filter and clock are alive try different jFETs in the sampling channel ...

if all these tests pan out then you're ready to look at the noise source ...
do a search on how to deal with that part (a scope will help)

[gigimarga]

Thx a lot Eb7+9 (i love this chord...)!

I will try tonight to test as you wrote me.

[gigimarga]

nobody can help me, PLEASEEEEEEEEEE???

[gigimarga]

 

[gigimarga]

 

[oldrocker]

What did you use to build this?  PCB?  Prefboard?  Vero?  Did you order a PCB or etch it yourself?

[gigimarga]

I used the Tonepad's PCB...it was made by a friend of mine which is very skillful...

[gigimarga]

 

[~arph]

Post some pictures of the bottom of your PCB.

EDIT: Sharp and clear pictures... 

[gigimarga]

thx ~arph...i will try to get some decent photos...but what you can use for?

[~arph]

See if you have any shorts.

Next thing. build an audioprobe and find out where the signal path stops. (and of course you checked the sticky debugging thread )