Maestro - PS-1A Phase Shifter (197x)

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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theehman
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Post by theehman »

I have one of these on my bench right now and it has a bad 2N4302 on the output. Got some coming in tomorrow so hopefully that'll fix it.
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Post by Bernardduur »

theehman wrote:I have one of these on my bench right now and it has a bad 2N4302 on the output. Got some coming in tomorrow so hopefully that'll fix it.
Same problem as mine? LOL
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Post by pinkjimiphoton »

courtesy of fleabay!! i love it when they do this ;)

Image

Image

dunno if they're good enough to work from, if anyone is interested (these things were kinda like "baby" mutron phasers)...hope it helps somebody out!!
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Post by KindaFuzzy »

that poor fish cap on the right looks a little rough.

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Post by Dirk_Hendrik »

To work for what? Tracing? Laziness is the first step in making life easier ;)
Maestro_MPS-1_PS1-PS2-PS1A-PS1B_Phase_Shifters.PDF
(176.68 KiB) Downloaded 345 times
I don't know this one but I did know the Shin-Ei clone variant which is rather close. I used above Maestro schem to get it running again. That was a phaser that did not exactly excite me.
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Post by Max Cohen »

pinkjimiphoton wrote:courtesy of fleabay!! i love it when they do this ;)

Image

Image

dunno if they're good enough to work from, if anyone is interested (these things were kinda like "baby" mutron phasers)...hope it helps somebody out!!
I see if I can work out the replica board of this - shouldn't be a problem from the picts - time is indeed

thanks for this
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Post by Dirk_Hendrik »

I knew I had these somewhere but "hid" them in the wrong directory. These are the Shin-Ei version
resleymachine _black.gif
resleymachine silk values.gif
resleymachine_wiring.gif
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Post by pinkjimiphoton »

dirk,

this is the resley tone? or are the pics mislabled?

the resley tone is definitely not one of these, this has only 3 preset switches and a bypass switch, i had one of these...jesus...when the hell was 91? ;)

or am i confused ? (probable)

was, for what it was, a nice simple phaser. if memory serves, you could combine preset switches, too.
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Post by Dirk_Hendrik »

Resleymachine. Not tone.

This one:
Image

If I remember correct, a little different in how the LFO was built and exactly the same in the phasing audiopath.
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Post by pinkjimiphoton »

sure looks about the same, indeed...thanks dirk!
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Post by juansolo »

I've made a clone of a Maestro PS-1A Phase Shifter. The board was fabbed by Haberdasher from the Madbean forum based on a layout found on the interweb, no idea who did it. The 2n5087 on the input is backwards on the layout, as are all 6 of the 2n5485s. The HA17458 opamps we got from Tayda work, which is good as others we tried didn't. Also I added the RF suppressing caps on the back of the board as it was picking up radio most impressively beforehand. Finally I wired as true bypass by jumpering the slow switch connections using Josh's (1776 Effects) Optotron. There's a little bit of a vol drop when engaged, but it doesn't mess with the signal when not in use now.

It needs a 12v feed currently, that then gets reversed by a Madbean Road Rage board to give the required -12v / +12v. I tried charge pumps and just couldn't get as good a result as with a proper 12V feed.

Image

Image

Links to the project:
Layout - http://juansolo.demon.co.uk/stompage/sc ... layout.png
Transfer - http://juansolo.demon.co.uk/stompage/sc ... ansfer.png
Maestro Schematic - http://juansolo.demon.co.uk/stompage/sc ... ematic.gif
Oberheim Schematic - http://juansolo.demon.co.uk/stompage/sc ... ematic.pdf

Oberheim designed the effect and their schematic is easier to read. Also it runs at +/-15v which will increase headroom.

Sound clip:

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Post by juansolo »

Hmmm, shame I can't edit that post, I'd have put smaller pics up ;)

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Post by juansolo »

Found the fella who did the layout over on DIYSB. He's got an updated version of the layout here with the correct orientations:

http://www.aronnelson.com/gallery/main. ... alNumber=2
http://www.aronnelson.com/gallery/main. ... alNumber=1

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rsado
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Post by rsado »

Hi,

I recently bought a Maestro PS1A and although it is working it is not without some issues.

I noticed that in bypass when using humbucking pickups (Gibson SG) that it distorts, but when in effect mode, this does not happen, or at least it is not as drastic.

I also noticed that when switching in and out of the effect there is a noticeable “ffump” sound, almost like the signal ramping up.

Tapping on the box sometimes produces a popping sound. I am guessing a loose solder joint somewhere.

This pedal is almost 50 years old and all parts look to be original so I don’t expect it to be noise free or without its quirks. I just wanted to know if the “issues” that I have come across are indeed actual problems or they are just part of an old design.

That aside, this thing sounds great. I have several phasers and this brings something new to the table.

Thanks,
Robert

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Post by TWSpedals »

rsado wrote: 13 Feb 2021, 17:24 Hi,

I recently bought a Maestro PS1A and although it is working it is not without some issues.

I noticed that in bypass when using humbucking pickups (Gibson SG) that it distorts, but when in effect mode, this does not happen, or at least it is not as drastic.

I also noticed that when switching in and out of the effect there is a noticeable “ffump” sound, almost like the signal ramping up.

Tapping on the box sometimes produces a popping sound. I am guessing a loose solder joint somewhere.

This pedal is almost 50 years old and all parts look to be original so I don’t expect it to be noise free or without its quirks. I just wanted to know if the “issues” that I have come across are indeed actual problems or they are just part of an old design.

That aside, this thing sounds great. I have several phasers and this brings something new to the table.

Thanks,
Robert
You may need to replace all the electrolytics. They are getting to the age were they start to fail.

There is a trimmer that sets a bias point near the output, this may need to be adjusted to remove any DC offset causing that "thump".
Have a nice day!

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