FREEKOUT - boosted signal but no modulation

[Robusto]

Hey all,

As the title says, I finished the Freekout, and when engaged, I'm getting a boosted signal but no modulation. I can hear the whine of the generator, and it goes up and down if I adjust the pots, but no effected signal.

Checked all the part values, I don't see any solder bridges, here's the voltages:

Input 18.06V
Trim 50%
Pots all fully clockwise

IC1
683mV
35mV
35mV
-14.46V
38mV
38mV
38mV
14.37V

IC2
-1.3mV
.58mV
-16.5mV
.58mV
-14.5V
4.1mV
0
14.87V

IC3
8.8V
7.38V
7.49V
11.76V
11.75V
14.87V
11.7V
11.7V
7.8V
7.53V
.56mV
5.64mV
_
1mV

IC4
0
1.3mV
0
-14.5V
2mV
2mV
2mV
14.87V

IC5
-14.49V
-6mV
-4.9mV
-14.5V
-14.5V
-4mV
14.87V
_

IC6
1.9V
7.97V
.7mV
-6.64V
-14.5V
2.5V
1.4V
14.8V

REG
17.74V
.36mV
14.87V

[Robusto]

Ok, nothing? Here’s some more:

I reseated all the ICs. I changed out the shift and mod pots for new, as the first ones I used had been salvaged from a previous project. I started tracing with an audio probe and started getting an effect signal all the way to the end. I plug a guitar into it and I am getting effected signal, but the pots have no effect. The signal stays the same no matter which way I turn them.

Annoying.

[madbean]

All your voltages seem fine. Slight difference in pin9 of IC3 but that's okay b/c that pin does nothing. Audio all the way through but no ring mod would make me suspect either the ICL8038 or AD633. But, again your voltages seem to be okay there.

Where did you get those two chips from?

PS I do not recommend replacing any parts until the problem is narrowed down a bit more (generally speaking).

[Robusto]

I got the 8038 on eBay from here:

https://www.ebay.com/itm/2PCS-INTERSIL-ICL8038CCPD-ICL8038-Waveform-Generator-Oscill-Gen-DIP-14-IC-New/291565457594?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Looks like they're still in business with a 99.8% rating, although the top review says "Counterfeit IC’s all 5 where bad. Replaced with another vendors product all work
5PCS National Semiconductor LF351N LF351 JFET Input Op-Amp and Machined"
Sooooooooo.....hmmm. I bought two of them and have tried both.

I got the AD633 from Mouser.

Sounds like maybe the 8038? Would be nice to have one from a legit source. Does anyone besides Small Bear sell them?

Thanks for the reply!

[Robusto]

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