MXR Phase 90 Schematic

[SamIV]

Can't seem to find this. PC Board says year 2001 and only has two chips, not the early model. Will not turn on. Battery gets very hot. Can anyone direct me in the right direction for the schematic?

Thanks,
SamIV

[stinkfoot]

If the battery gets hot, the power is shorted. Check the polarity protection diode (one of the ones right below the adapter jack) and the filter capacitor (large electrolyte can also in the proximity of the jack).

[SamIV]

Thanks stinkfoot. One of the diodes is bad.

[jay42]

Originally Posted by SamIV

Can't seem to find this. PC Board says year 2001 and only has two chips, not the early model. Will not turn on. Battery gets very hot. Can anyone direct me in the right direction for the schematic?

I know you're sorted out, but two chips...really? What's printed on them?

[SamIV]

I will have to look tomorrow for you. Left it at my office.

[stinkfoot]

Most likely, it's a TL062 (DIP8 dual op-amp) for the input stage and LFO, and a TL064 (DIP14 quad op-amp) for the phase stages.

The earliest ('70s) Phase 90s used six single op-amps, and when the block logo era was established in the early '80s, they switched to three dual op-amps. Later still (around 1990) when Dunlop redesigned the pedal to the form we're used to now (with the jacks/switch mounted to the circuitboard) they went to a quad op-amp for the phase stages.

/Andreas

[SamIV]

The chips are TL064CN and TL062CP. Hope this helps.