MXR auto phaser schematic

[Johnny1234]

I have been looking for a couple of years now, to no avail.
Would rather find cause of failure than shotgun the whole
Thing.
Many thanks
John

 

[Tubetec]

Looks like vactrols ,

 

[Khron]

The failure being....?

 

[Johnny1234]

No output, but not dragging down power supply.

 

[CJ]

is that the

MXR M-110 Auto Phaser​

?

might have to trace it out,

you have a o scope?

 

[Johnny1234]

Hi CJ
Dosn't say any except pcb says MXR AP on the rear. Also serial # begins with P
Yes have scope, nice teletronix.

 

[Johnny1234]

is that the

MXR M-110 Auto Phaser​

?

might have to trace it out,

you have a o scope?

Yes CJ upon you suggesting I looked up pics and it is the M-110 Auto Phaser.
Now I have a clue, but still no schematic anywhere. If someone doesn't have
it here then it probably does not exist.
Many Thanks

 

[CJ]

I looked for a schematic for a Versatone Pan-O-Plex (Carol Kaye/Jack Cassidy) bass amp for about 2 years, somebody dropped by the forum and had one so do not give up hope!

first thing i would do is put an ohm meter across every blue tantalum cap on that board to see if it is shorted like tants do.

 

[Johnny1234]

I looked for a schematic for a Versatone Pan-O-Plex (Carol Kaye/Jack Cassidy) bass amp for about 2 years, somebody dropped by the forum and had one so do not give up hope!

first thing i would do is put an ohm meter across every blue tantalum cap on that board to see if it is shorted like tants do.

Thanks for that advice, that was the first thing I did, and then checked V+ to ground. All tested good.

 

[Bo Deadly]

Probably something like this (nope - see schem in post #14):


Credit: https://www.elektormagazine.com/news/small-circuits-revival-34-phaser

But with all LM741, carbon comp resistors, non-standard format and tantalums, I'm not sure if I would get emotionally attached to this.

If I just got that itch to hack, I would probably take a hot air station to it and literally remove ALL of the parts, measuring resistor values along the way and trace it out. Careful not to burn out the vactrols. They might still be good.

Then I would replace with TL071, metal film resistors and new caps all-around.

 

[gyraf]

..with your symptoms, just replace all power-rail tantalum drop capacitors with electrolytics - tants has no place in power, as they're known to fail short..

/Jakob E.

 

[DanMcCullough]

I have the schematic. I. And see from your pick that the tantalums have already been replaced. Those are not originals. Do you get an output when the switch is out and nothing when the switch is in? Or nothing regardless of the bypass switch position?

 

[Johnny1234]

I have the schematic. I. And see from your pick that the tantalums have already been replaced. Those are not originals. Do you get an output when the switch is out and nothing when the switch is in? Or nothing regardless of the bypass switch position?

Hi Dan, I really don't remember as it has been on the shelf a couple years. Tomorrow I will rebuild the test jig and find out. BTW is the V+ 9 volts.
I will keep you posted.
Many Thanks
John

 

[DanMcCullough]

The +V should 24V. That is what the original MXR Professional Products Rack power supply is.

 

[Johnny1234]

The +V should 24V. That is what the original MXR Professional Products Rack power supply is.

Very cool Dan. Thanks a million, now I've got my project for tomorrow. I know this will make a lot of people very happy.
Also a big thanks and happy holidays to all members of the Group DIY.

 

[DanMcCullough]

You’re welcome. I think that +15V will work as well if you don’t have +24V available.

Yes happy holidays to all members of the Group DIY.

 

[Bo Deadly]

Looks like most amps are using raw V+ but the oscillator and certain reference voltages are using 10V with a Vg of 5. So a stiff 15V would probably work fine.

Note that it looks like you need to connect pins 9 and 10 together to close the CV connection. Otherwise, depending on trimmer R37, the LEDs could be 100% on (200 ohms for VTLC52) and most signal is just getting shunted. With the high noise parts, this might be perceived has simply no signal at all.

 

[CJ]

Is that MPS5172?

How much to get a board fab together? Might be a cool project, new 741's might be lower noise, but you could socket the board and stuff some burr brown in there for kicks,

anybody ever heard one? is it really the holy grail of all phasers or was that Reverb hype sales pitching? i will check youtube for some lo-fi mp3 samples,

cool on the schematic and thanks! oh, and happy holidays ,
i'm gonna get hammered drunk on 10 High, jus kidding.

 

[Johnny1234]

Is that MPS5172?

How much to get a board fab together? Might be a cool project, new 741's might be lower noise, but you could socket the board and stuff some burr brown in there for kicks,

anybody ever heard one? is it really the holy grail of all phasers or was that Reverb hype sales pitching? i will check youtube for some lo-fi mp3 samples,

cool on the schematic and thanks! oh, and happy holidays ,
i'm gonna get hammered drunk on 10 High, jus kidding.

Yes it appears to be MPS5172 transistor. We used these at Media Sounds in the 80's and they were used a lot. Also have two close friends that love them and they are not lo fi nuts as they both produce records on the Amek 9098.

 

[CJ]

Here is a print of the auto phaser with the part numbers and values drawn in.

some were hard to read, they are the ones with the red print, if anybody can figure out those guys then that would be great!