Vintage EHX Silencer power mystery

[Strategy]

I was given a vintage Electro-Harmonix Silencer that works beautifully on battery but won't accept power adaptor. Looks like it wants +9V 3.5mm positive tip, which I'm able to give from my One Spot with one of the little 3.5mm adaptors.

The power jack has not wired ground connection, just +V to the pcb, so I assume ground is made via the jack sleeve to enclosure. I've had it on very old gear where corrosion on the jack or box kept the ground from connecting in this scenario, so I swapped in a new 3.5mm adaptor. No dice.

I see in the schematic here http://www.muzique.com/schem/silencer.jpg that AC power comes into Q1. Pretty safe to assume that the issue lies here? Just seems like if that transistor was toast, the unit would also be non-functional via battery.

Suggestions welcome! This pedal is really nice for quieting between-notes noise from my hum-prone Univox Hi-Flier Bass, which seems to pick up phantom  buzz depending on where in my studio I'm standing, whether Mercury is in retrograde, etc.

[Rob Strand]

Based on the schematic, and assuming it is correct, when powering from the adaptor it needs the battery to be present!  That's an insane and unintuitive power scheme.

You could certainly make some simple mods to the power supply to change that.  For example adding a resistor (4.7k?) between the base and emitter collector of the power supply transistor, perhaps even adding a 9V1 to 10V zener from the base to ground of  the same transistor.  However, in order to stop those mods dumping current into the battery you really should change the slide-switch wiring.

EDIT: Fixed typo.

[Strategy]

WOAH, I'm just realizing I had not tested the power with a battery there as well. OK I'll try this! What the heck, what a strange design.
I also don't know why it would have an on-off slide switch when it also has a footswitch. This also strikes me as a strange aspect of the design.
I thought about really modding this thing with true bypass switching and boss power supply...maybe I still will.
OK, off to test this again.
THANK YOU!
Strategy

[RickL]

Without the switch (in the off position) the battery will be supplying power to the circuit all the time, even when the footswitch is in the bypass position and even if a guitar is not plugged in.

Current effects are set up so when you pull the plug from the input jack, it disconnects the power to preserve the battery. Not this one, if, as Rob mentions, the schematic is correct.

[PRR]

> don't know why it would have an on-off slide switch when it also has a footswitch

The ON/OFF powers-up the "works". You do not change this on-stage, it will thump.

The footswitch routes audio through or around the effect.