Maestro PS-1 Phase Shifter Questions

[JeffersonRhodes]

Hi,
I'm not too knowledgeable about electronics in general, but can do some minor repairs etc.

That being said...

I recently came across a Maestro PS-1 Phase Shifter. This thing is from the 70s and I use it through a Rhodes electric piano. My question is probably pretty simple to answer or at least I hope it is.

Common with vintage equipment, there is a low 60 cycle hum coming from this pedal. What can I do to help reduce the hum? Can I add copper shielding inside the pedal?

Also, this pedal seems to cut the volume quite a bit. Is there some tweaking that can be done so I can keep my volume at a decent level??

Thanks!
Matt

[Mark Hammer]

Hmmm. Could be that your hum and level problems are linked.

Do you have a schematic for it?

[JeffersonRhodes]

Hmmm. Could be that your hum and level problems are linked.

Do you have a schematic for it?

I do have a schematic for it.



Does this help at all? I would love to get in there and tweak with the tone and phasing, do you think that's possible?

Thanks for the help!
Matt

[Enzo]

First thing I'd do would be to make sure the +15 and -15 volt supplies are close to their proper levels. COnsidering the minimal expense, and the age of the parts, I would replace the two 470uf filter caps in the power supply as well.

I would loosen and then remount all jacks to make sure they have a fresh contact with ground - the chassis.

Is this lower level signal only in effect mode, or is it diminished in bypass as well?

[JeffersonRhodes]

It does not diminish the bypass, but I can hear quiet "clicks" in the background of the phaser still in action waiting to be kicked on.

[lowell]

I had the same problem w/ mine. Replaced the filter caps. Then realized the voltage rails were 12v and -8v. Replaced both 15v zeners and voila. True test will be tonight on the gig to see if it's still noisy. Oh and also added an input buffer which fixed the tone loss issue. Will report back on results after gig.

[lowell]

all good now!