Another phase 90 problem

[flintstoned]

Had a stock phase 90 I modded the crap out of, (added knobs for intensity and eq shift and three toggles for script, tremolo and wave form mods) and it sounded great except for an occasional short if I bumped the output cable just right. So I thought I'd clean it up a lil bit inside because it was all crammed in there pretty tight. So I found and fixed the short and when I was squeezing it all back in the box, I broke the stock speed pot. After some cussing and thinking about the saying "if it ain't that broke, don't fix it" I ordered and replaced the pot and now I lost my phasing, just have a clean output. The flashing rate led still pulses with the speed of the phasing and I audio probed the outputs on the tl604 chip and only have the clean signal coming out there also. So I'm wondering if anyone knows, shouldn't the chip be where the phasing sound should begin?

[BadIdeas]

If you damaged the board where the speed pot goes, it might prevent the LFO's output from getting to the JFETS. Look up "The Technology of Phasers" on geofex. If the voltage at the gates doesn't change, there will be no phasing.

BTW, have you considered rehousing your Phase 90 in something roomier?

[flintstoned]

Okay, I measured the voltages on the jfets, and they all were consistently varying, so I guess its good up til there. I have checked the board numerous times for cracks but haven't found any, but I've been doing this long enough to know that no matter how many times I checked, that I still can't rule that out!

[flintstoned]

Changed all mods back to stock, still no phasing! If I had any hair, I'd rip it out! 

[BadIdeas]

I am having a hard time with this. Another possibility is that since the trimpot (R27) seems to be used to add a DC offset to the JFETs, maybe it is either broken or accidentally maladjusted. Also check the resistors along the way. The JFETs' voltage may be varying consistently, but if it is in the wrong range, maybe there is no noticeable or audible change in the resonant frequency of the RC filters at the TL604's inputs.

DISCLAIMER: See signature.

[flintstoned]

Well I checked the trim pot an its working ok. Also checked all resistors for shorts and changed the caps near where the stock pot was located in case one of them snapped a lead. Still no luck. 

[flintstoned]

For future searchers and troubleshooters: replaced tl064 to get phasing back, all is well