Super Phaser question (resistor replacement)

[pinkjimiphoton]

Why don't you just use 3x 100K~120K instead of R19, R20 and R23?
Gain and mix will remain the same...

BTW
R26 can be any other higher value, if saving 150Ks is a must

yeah, 100k is fine this is basically a phase 90. a slight mismatch, with 150k on one side and 100k on the other can add a bit more "vibe", but more than say 20% off tolerance and the circuit will suffer.

[jfrabat]

Why don't you just use 3x 100K~120K instead of R19, R20 and R23?
Gain and mix will remain the same...

BTW
R26 can be any other higher value, if saving 150Ks is a must

yeah, 100k is fine this is basically a phase 90. a slight mismatch, with 150k on one side and 100k on the other can add a bit more "vibe", but more than say 20% off tolerance and the circuit will suffer.

I already found the 150K, but its good to know this stuff!

If you have a 250k pot (not a trimmer), you could see what the two resistances are on each side of the wiper, and substitute fixed resistors for the trimmer...assuming you have those values on hand.

I think I'll just try to find a trimpot locally.  There are 2 places I still have to hit (they are a bit far, though!).

[reddesert]

I don't mean to be rude, but I think messing around with the trimpot bias when it's not at all clear that the rest of the circuit is operating or that your voltage values are correct is going to take you around in circles of component replacement without understanding what is happening.

The zener diode is supposed to hold its positive end at approx 5.1 V. That is connected to the trimpot log 3. If you have 1.15 V at the zener and the trimpot leg, then something is wrong.  This goes back to the question of why all the op-amp pins are at ~ 1.15 V (and how that could be if the FET sources are at 4 V, since they should be connected to the op-amps).

You can test the voltage at the zener and the pad for trimpot leg 3 without actually having the trimpot in the circuit, so you don't need to wait for the replacement.  It should be ~ 5 V.

Trimpots can be damaged by overheating, but it should be possible to solder one in without damaging it - typically I only hold the soldering iron tip to the component for a few seconds until the solder just flows ontp it and the pad. Desoldering usually takes more effort and is more likely to damage components, so if a component is bad after desoldering, it doesn't mean it was bad before.

[jfrabat]

I don't mean to be rude, but I think messing around with the trimpot bias when it's not at all clear that the rest of the circuit is operating or that your voltage values are correct is going to take you around in circles of component replacement without understanding what is happening.

The zener diode is supposed to hold its positive end at approx 5.1 V. That is connected to the trimpot log 3. If you have 1.15 V at the zener and the trimpot leg, then something is wrong.  This goes back to the question of why all the op-amp pins are at ~ 1.15 V (and how that could be if the FET sources are at 4 V, since they should be connected to the op-amps).

You can test the voltage at the zener and the pad for trimpot leg 3 without actually having the trimpot in the circuit, so you don't need to wait for the replacement.  It should be ~ 5 V.

Trimpots can be damaged by overheating, but it should be possible to solder one in without damaging it - typically I only hold the soldering iron tip to the component for a few seconds until the solder just flows ontp it and the pad. Desoldering usually takes more effort and is more likely to damage components, so if a component is bad after desoldering, it doesn't mean it was bad before.

That's not rude at all.  It is actually very good advice, which I will follow!  I will retest the voltages tonight.

[Fender3D]

yeah, 100k is fine this is basically a phase 90. a slight mismatch, with 150k on one side and 100k on the other can add a bit more "vibe", but more than say 20% off tolerance and the circuit will suffer.

That's why I suggested 3x 100k Jimi
you may figure that circuit block as an inverting op-amp mixer: R19 and R20 are the input resistors and R23 is the feedback (gain) resistor...

BTW
follow reddesert's advice.