Dean Markley Overlord not working

[TarheelTechinTraining]

So I have just fixed the switching and now this things still not right. When I engage the pedal there is a "motorboating" sound when I turn up the "drive". Any idea where I should start looking?

[pdf64]

Motorboating is usually oscillation resulting from a positive feedback path between stages via the HT, usually due to inadequate (or failing) HT decoupling, eg bad electrolytic in power supply.

[TarheelTechinTraining]

OK so I checked the electrolytics in the power supply, all good. Then I started turning knobs to see if I could change the noise. If I turn the mid and bass all the way down the noise stops and the pedal sounds good, though high and thin. Any suggestions on the culprit?

[pdf64]

How did you check them?
Unless you use a good meter specifically intended to measure ESR, the best test is to tack a good one in parallel.
Measuring the cap value may not help, as the accuracy to value may not be the parameter that's the problem.
Could you put a schematic link on to this thread

[TarheelTechinTraining]

OK so I've gone ahead and replaced all the electrolytics since I had them. But still doing the same craziness.

[52 Bill]

In fixing the switching, you replaced Q1 right? What did you replace it with? If it is not turning off fully it might cause a problem.

Have you tried replacing the tube?

[TarheelTechinTraining]

I replaced Q1 with a 2sk30a and I did try a known to be good tube. Thanks again

[TarheelTechinTraining]

If I removed Q1&Q2 the pedal would be always "on", right? I'm testing if I goofed some how in fixing the switching. Or if there's a problem with the effect

[52 Bill]

If I removed Q1&Q2 the pedal would be always "on", right? I'm testing if I goofed some how in fixing the switching. Or if there's a problem with the effect

Yes, Q1 turns on and off the clean signal path and Q2 lowers the gain of the tube drive circuit. If you remove them both the pedal should remain in the distortion mode.

[TarheelTechinTraining]

So I removed Q1 and Q2. Now the volume is low and not much drive. When I toggle the pedal I can hear it. Also the mid and bass are there but the high seems to drop the distortion. Any ideas?

[52 Bill]

So I removed Q1 and Q2. Now the volume is low and not much drive. When I toggle the pedal I can hear it. Also the mid and bass are there but the high seems to drop the distortion. Any ideas?

Is you pedal wired like the schematic that you have posted? Specifically the two fets.

[TarheelTechinTraining]

Yes its the same. Though there are some discrepancies. Q2is a 2sk30a, on the pedal but a 2n4348 on the schematic. Also c3 is 47uf and c4 is a .022uf on the pedal but different on the schematic. The parts seem stock, never been removed as far as I can tell.

[52 Bill]

Yes its the same. Though there are some discrepancies. Q2is a 2sk30a, on the pedal but a 2n4348 on the schematic. Also c3 is 47uf and c4 is a .022uf on the pedal but different on the schematic. The parts seem stock, never been removed as far as I can tell.

My point was is the wiring the same as the schematic. The schematic shows that the two fets are used to turn on and off the direct signal path and when the distortion is turned off, it lowers the gain of the drive opamp by shorting the input and output together. Removing both fets should not have caused the problems that you now have, unless the fets are wired to do something other than what the schematic shows.

Try re-installing only Q2 and see if the distortion at least works like it did before.

[TarheelTechinTraining]

I've reinstalled Q2 and there is distortion though not much. With the effect toggled,pedal on, and drive all the way down it sounds the same as toggled off, no effect. Do ya think that IC1 is bad or maybe VR4? Its got +12v on pin8 and -9v on pin4 of IC1

[52 Bill]

I've reinstalled Q2 and there is distortion though not much. With the effect toggled,pedal on, and drive all the way down it sounds the same as toggled off, no effect. Do ya think that IC1 is bad or maybe VR4? Its got +12v on pin8 and -9v on pin4 of IC1

Check the voltage on the rest of the pins like 1 and 7. I'd also try and find out why the two voltages are different +12 and -9. It may be easiest to replace the chip and see if the voltages come back and the effect works.