The Sweeper No 866 MIJ Phaser Pedal

[mort]

Here's another odd bird that was acquired recently. Unfortunately this one does not work. It passes signal and with the effect on it makes just the very slightest teeniest bit of phaser effect... and I mean just barely.

I'd like to have it working as a cool weird piece in my collection but tbh, I'd rather someone else fix it for me. I'm better at building things new than at troubleshooting when it comes to pedals.

Anyone here have strong phaser knowledge and some interest? I can send paypal, gear or nudes from Central Florida. Just kidding about the nudes... kinda.

All I've done to it is cut out a poorly implemented LED and power jack and connect the battery clip to + and -

[nosaj]

You might be surprised just changing those electrolytics may bring it back to life.
nosaj

[vintagekiki]

The Sweeper

https://www.freestompboxes.org/viewtopic.php?t=14712

https://www.freestompboxes.org/viewtopic.php?p=167708#p167708

TA75747P = ľA747 = dual 741

[dmeek]

From photos I've found, here's the schematic



edit: fixed some minor mistakes

[Mark Hammer]

It appears to be a basic meat-and-potatoes 4-stage phaser. The unique aspect is that it uses long-out-of-production 14-pin dual op-amp chips. That suggests it is at least 40 years old.
Regardless of which particular FETs it uses as control element, ALL such FETs will require optimum biasing to sweep, hence the trimmer by the footswitch. Chances are very good it is used to set the bias applied to the four FETs. Adjusting it will not damage anything, so proceed fearlessly. The worst that will happen is that you'll dial in a bias that pushes the FETs out of sweep range.

The trick that MXR used for the Phase 90 and 45 was to drop the supply voltage down to around 5V, using a zener diode, and derive the bias from THAT. This assured that, whether the battery was brand spanking new, at 9.6V, or had run down to 7.5V, the bias voltage would be derived from a predictable source. Honestly, the things that relying on batteries made us do in the '70s!