Mxr phase 90 repair

[9 volts]

I all, I have a phase 90 that needs repair. The unit doesn't work but the 5.1 zener diode gets really hot, so I can't really leave it on too long to test. Would this be caused by a short?
Thanks

[PRR]

the 5.1 zener diode gets really hot

That ain't right.

Did you just build it? Fix it? Did it fall off a truck? Battery or power-pack? Polarity checked?

SCHEMATIC!!!

[Rob Strand]

I all, I have a phase 90 that needs repair. The unit doesn't work but the 5.1 zener diode gets really hot, so I can't really leave it on too long to test. Would this be caused by a short?

The zener is fed by a resistor.   There's going to be a short between the supply and the zener, which is the Vref supply rail.    Use your multimeter.

[Mark Hammer]

That sounds especially plausible.  There's a short somewhere that is drawing more current than it should.

[antonis]

Finally, is that Zener 5V1 or 3V..??

[9 volts]

Yep. 5.1 zener. I'm away from it for a few days, but when I get back to it I'll check the voltages to see it there is a short. I did do an audio probe and noticed one of the op amps on the tl064 want getting any sound. This is a Dunlop model and uses one tl072 and one tl064.
Thanks again, I haven't posted for a while and it's great to see it's still a fantastic community of support!

[9 volts]

All systems go! The tl064 had blown, the reason the diode was getting hot was that I'd put the 5.1 zener in the wrong place! I read that the Zener was is diode 2 position (as written on pcb), but this is incorrect, that's the 9 volt protection diode position. Once this was sorted I had to adjust the trim pot to get more phase effect.
All good!