MXR Phase 100 Repair Help

[pedalbob]

Thanks again for the help.  Had a slow weekend so worked on it some more. I was getting some "different" readings at one of the tantalum capacitors in the oscillator circuit so I changed it along with the diode which was hooked to it.  The weird thing is now I am getting much more effect but only when I have a weak (reading about 6.8V on my meter) 9V battery installed.  I have two wall warts I 've tried ... one reads just over 9 volts (9.2) and the effect weakens. The other reads about 12v and I hear almost no effect with that.

When I put the weak battery in my "good" pedal it have very little effect ... It sounds great either wall wart.
I've also tried different positions with the trimpot on the "bad" pedal and it is responsive but can't get it to sound as full as the "good" unit.
(Think of like a Phase 45 vs a Phase 90 on max.)
I read somewhere else that phase shifters can be touch with power supply but I 'm stumped why the one is working better with a weak battery.

[Govmnt_Lacky]

Hmmm.... this may be a long shot but, are you sure that the diode in the circuit (should be a 1N914) wasn't accidentally switched with a zener diode?

[pedalbob]

Success !
I had replaced the 4 ZTX109 transistors with 4 2SC1849 that I bought online from a reputable source and they eliminated the effect all together. So I tested them and they don't even test as NPN transistors so guessing they were counterfeit or gone bad.
So I put 4 BC183 transistors in which is close as I could find to the original obsolete ZTX109's and voila the pedal works great now.

So anyone looking for a replacement for the ZTX109's or the 2SC1849's which seem to be the 2 types of transistors in the older MXR Phase 100's I can say that BC183 which are still available work well.

At this point I pretty much replaced everything in the LFO circuit except the resistors and the 1 Op Amp. 

I also replaced 1 of the Vactrols with a newer available one that has a slightly higher forward voltage on the LED side but still works fine (all of the discussion I've read about factory matched Vactrols doesn't seem to make a big difference at least to my ears testing back to back with my repaired pedal and a 100% stock one of the same vintage ... actually slightly older).

Thanks to everyone for the help and encouragement.

On to my next project ...