Maestro PS-1A not working

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Beedoola
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Post by Beedoola »

I have my friend's PS-1A Phase shifter here (with footswitch). The pedal does not phase at all. The trim pots were the stock ones and seemed to be intermittent/not working - pressing them (or one in particular) would cause some phase sound to occur but then die out. I replaced all 3 with new 10k trimmers (same value as stock). However replacing them didn't seem to fix the problem.

I've read other posts (either here or on some other forum) that the trimmers are highly sensitive and shouldn't be messed with :)
I've not sure if the lack of phasing is due to my not having the trimmers set up correctly, or that it is something else all together that is the problem. The schematic gives instructions on how to set them, I followed said instructions and was unable to even get some phasing effect.

Any spots I should starting checking? Electro-caps?

Here is a gut shot and the schematic:

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theehman
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Post by theehman »

Check the solder joints on the ICs. Pressing on the trimpots may be causing intermittents on those. I had one for repair that had oxidation on the IC legs and was causing a no-phase problem.
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Beedoola
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Post by Beedoola »

Does it appear that the ICs were replaced ? Only one of them is a 1458...

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Govmnt_Lacky
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Post by Govmnt_Lacky »

Definitely looks suspect....

You mentioned that the phase was intermittent when you would touch one of the trimmers. Was it the trimmer next to the suspect op amp? If so, you might be on to something.... :secret: Bad solder joints or oxidation....
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Dirk_Hendrik
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Post by Dirk_Hendrik »

In 2.5 yrs the only progress is noticing a changed opamp and the suggestion to tweak a trimmer!? :shock:

- Supply voltages measured and correct?.
- Waveforms. Does you LFO work
- Signal? Dry available?
- Signal? unmodulated wet available (remove dry from output)?

etc. etc. Start working. This is most likely a "within the hour" repair.
Sorry. Plain out of planes.

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Beedoola
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Post by Beedoola »

Govmnt_Lacky wrote:Definitely looks suspect....

You mentioned that the phase was intermittent when you would touch one of the trimmers. Was it the trimmer next to the suspect op amp? If so, you might be on to something.... :secret: Bad solder joints or oxidation....
I changed the trim pots, an electro cap, and a resistor.

Dirk_Hendrik wrote:In 2.5 yrs the only progress is noticing a changed opamp and the suggestion to tweak a trimmer!? :shock:

- Supply voltages measured and correct?.
- Waveforms. Does you LFO work
- Signal? Dry available?
- Signal? unmodulated wet available (remove dry from output)?

etc. etc. Start working. This is most likely a "within the hour" repair.
dude let me have the pedal, and it sat not looked at since.
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Beedoola
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Post by Beedoola »

is there a reason you can't edit posts on this forum????

The Dry signal works. The trimpot for the output works. When I engage the controls, I get nothing, no phase.
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Beedoola
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Post by Beedoola »

voltages are good. LFO works - I can hear it ticking and changing when engaging the different controls. Just no Phase.
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Beedoola
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Post by Beedoola »

weird occurrence. When the Slow Phase is in the OFF position, the LFO works and you can hear it but the effect is more like a term, slightly gain, not phase.

With the Slow in the OFF position, and the other two in their respective ON positions, you hear the LFO vary.

When the Slow switch is moved to the ON, or down position, the LFO is bypassed...
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Post by Parnellio »

I have one i've just fixed. Got it for $150 (CAD) with the Maestro Jester drum machine too.

I had to replace the output transformer, cause mine made no phase but passed signal. And a couple of dry joints plus an obviously smashed fuse holder.

Make an audio probe and find out where signal is getting to.

You can also probe pin 1 on the IC which controls the Oscillation feed. It's the one by its self, not the 3 inline. That should produce an audible clicking in tempo of the phase.

Not sure how to share photos here. But I can help if you still have issues with it.
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Parnellio
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Post by Parnellio »

Also when I replaced the output transformer I read the schematic from the bottom, not the top for the pinout ...

Anyway, cut a long story short, mine did exactly that, backwards...off was on, on was off... but all fckd up.... The output JFET was in wrong. wrong pins in the wrong holes...

There's a few ways to determine if this is the case. (voltage checking primarily) But best to double check the pinout.
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