electric mistress voltage regulator doesn't regulate! whats going on?

[antisolo]

I know I already posted something about this but I'm not super computer savvy and new to this forum so bear with me.

This 18v 70's electric mistress is driving me insane. Here's the schematic:
http://www.freeinfosociety.com/electronics/schematics/audio/pictures/electroharmonixelectricmistress.gif

I tried replacing the 741 op amp at the power input multiple times and tried tons of different transistors and diodes in that section. The pedal works fine if I bypass all that and just hook up 9v to where the 12v are supposed to be but I feel like I should do this right.

It seemed like there was a mistake in the schematic with 2n5037 (obsolete part) transistor. If i put a transistor in backwords (switch collector and emmiter) it works and different transistors do put out different voltages. However if I plug the unregulated power supply that electro harmonix gave me the voltage coming out increases and started frying out some of the transistors I tried.

Do you guys know of any way that I can put a useful voltage regulator circuit in this thing? I haven't found any information on one that looks the same.

[theehman]

It's a 2N5087.  It was replaced in later units with a 2N4354

[antisolo]

Thanks! I did try the 2n5087 but the other components still don't seem to be doing anything to actually regulate the voltage. The op amp puts out 18v with 2 batteries and puts out 26v with the electro harmonix power supply which is also putting out 26v.

[theehman]

Did you check the transistor or zener diode at pin 2 of the 741?

I've got a couple of these on the bench with the same problem and I'm sorely tempted to just put some 3-terminal regulator supplies in them.

[antisolo]

Yeah I've messed around with the pin 2 diode/transistor as well.

I'm tempted to do the same with the 3 terminal regulator as well although I haven't really worked with those much. Any recommendations for a good part? I'm working on this for a friend so I'd have to see what he wants me to do but I'd hate to not keep it in it's original condition.

I was also thinking of bypassing the regulator and just giving it a 12v power supply which might be a less permanent modification.

[theehman]

I would just use a 12v regulator, maybe set up to do 13v, like a 7812.  It's just a power supply, it's not going to affect the sound.

[antisolo]

Ok awesome thanks so much for the help.

[antisolo]

wait i should be able to just use this circuit here right?

http://knol.google.com/k/-/-/1f4zs8p9zgq0e/2q8egv/78xxpinout.jpg

and are those capacitor values good for an input of 18v to 26v?