Sunn Beta preamp in vero - pesky opamp oscillation

[Sesh]

Hi there!

I'm building a Sunn Beta preamp for my bass rig from this vero layout: https://1.bp.blogspot.com/-ceaA4o2mVGI/XzldcO6V7dI/AAAAAAAADAs/HvUlx60GbhMjywHdv_NUsonJApT7fn18wCLcBGAsYHQ/s1534/sunn%2Bbeta%2Bpre%2Bamp%2Bbass%2Blead%2Bswitch.png

Schematic's here: https://www.freestompboxes.org/download/file.php?id=26188&sid=1468741dc9da2ed04dd9beff314d800d&mode=view
Keep in mind the bass/lead switch that adds parallel capacitors

Alas, it currently oscillates at the IC4 (RC4558) opamp. I've traced  the oscillation - it is just barely audible before the 330k resistor going from pin 2+3 of IC3. Then on the row on the other side of the 330K with the 2 uF bipolar electrolyte it becomes very loud. I can hear the opamp amplifies the oscillation from the input to the output at pin 7.

I tried my usual go-to's for vero - making sure there's no copper burs or remains on the lines, resoldered several times for proper soldering, checked component values and placements. Changed ICs. No luck.

Any ideas for further troubleshooting?


Voltages as follows:

1  7,5V   8  8,2V
2  7,5V   7  7,0V
3  3,7V   6  7,0v
4  0,9V   5  3,8V

[antonis]

Both op-amp outputs are saturated..
Also, non-inverting inputs are forced to voltage level other than GND..

Could you plz post some pics of your build..??

[Sesh]

Interesting... and sure thing! Hope these are detailed enough