EHX Vintage Polyphase with dc jack layout

[nik55]

I saw a thread with someone rebuilding this pedal.
That one had a transformer in it.
The Canadian ones did not: instead using an external wall adapter (24ac 250ma)
and a dc jack.

If your unit has ticking, that's coming from the wires on the Env / Sweep switch being too close to U7 or U9.
Some chopstick movement of the wires solved it.
Move them off to the left and it will pretty much go away.
Not sure how to get these images in here but I think you can download them.

Here's the layout for mine with the schematic changes compared to the pcb.
All the electrolytic caps in mine finally went way off spec so I replaced them all.
The new polyphase doesn't seem to sound much like this one.

[armdnrdy]

So..

You completed a build for this?

Can you post the PCB file?

EDIT:

I think that I misinterpreted your post because you posted a layout.
So you reverse engineered the factory Canadian version. Correct?

[nik55]

Yes that's it.
I drew the board for the one I have.
It's a great sounding unit with a great warm full sound and a cool envelope phaser  in the env section.
the harder you hit it the more the phase goes up and down type thing.

I think there were some guys trying to build a new pcb here:
http://www.diystompboxes.com/smfforum/index.php?PHPSESSID=e7675746c6226d0ff31d22f17d9ee845&topic=100570.40

[analogguru]

I think in the schematic it should read:
R4 5k6
R5 240k

[armdnrdy]

I think there were some guys trying to build a new pcb here:
http://www.diystompboxes.com/smfforum/index.php?PHPSESSID=e7675746c6226d0ff31d22f17d9ee845&topic=100570.40

Yes..I believe that he finished it up.

http://www.youtube.com/watch?v=OXL0z3bVJAE

How does his "clone" sound compared to your original?

[nik55]

It sounds different.
He made some changes to it so it's not a direct part for part clone.
The envelope stuff is way more subtle on my pedal.
It's a very subtle long phase or a quicker one but it all depends on how hard you hit the notes
and how high the sensitivity is set.
It's really better for single note runs.
Also don't forget that the old EHX pedals boosted the guitar volume substantially as well.

The regular phase is a nice deep fat sounding type of phase.
He has it up high with a lot of feedback.
You get the spacey sound but you are not hearing the typical phaser stuff on the demo.

There was a demo of the original on youtube but it's set on sweep and the guy is turning the envelope controls .
They don't work on that setting.I'll see if I can do a simple sound file to give you an idea.
I only have a crap solid state amp working at the moment but it might be good enough.

[nik55]

Noticed a slight goof near the rectifier section on the board layout an extra little bit of track so I corrected it.
Took a stab at redrawing the power section.
How critical are the voltages?
Mine has about 26-28 volts ac getting knocked down to about 16.1.

[armdnrdy]

Hey Nik,

I missed your reply about the sound comparison. If you can post any sound sample...it would be appreciated.

I tried to download the new schematic that you posted but the file comes up black. I think that something happened when you uploaded it.

The power section is regulated with the 1N965B 15 volt zener and NPN transistor.

The 16 VDC you are measuring in fine. Transformer output voltage can vary and are dependent on the input voltage. You might take this effect to a friends house that lives 100 miles away and the voltage might be different than what you are reading at home.

[nik55]

Don't know if this is right but I tried it anyway.

upload pic

[GodSaveMetal]

Noticed a slight goof near the rectifier section on the board layout an extra little bit of track so I corrected it.
Took a stab at redrawing the power section.
How critical are the voltages?
Mine has about 26-28 volts ac getting knocked down to about 16.1.

Please post the PCB of THIS, yeahhh thanks man!!!

[Scruffie]

So wait, yours has the funny bit of circuit around T8 that makes the 'B>' connection?

[nik55]

I'm not an expert so I can't say if it's an odd way of doing it .
It goes from  T8 to a jumper down to r28 and r29 to pin 6 of U5.
You can see it on the board layout better.

Now the pedal works like so:
In Envelope mode:
all the controls work except for rate.
So Feedback can still have an effect on things.

In Sweep mode:
it's a phaser with the rate control and feedback control.
The envelope stuff is disabled.
Is the phaser section at all similar to an mxr phaser?

[Scruffie]

My unit and the gut shots i've seen haven't had that bit of circuit and connection, I assumed it was a weird red herring mistake on the schematic! Interesting... have to see what difference it makes.

[nik55]

If your unit has the transformer in it then the pcb layout looks slightly  different to me from the dc jack one.
They may have moved it around. I can't tell clearly from the pictures I've seen.
It's definitely there on the dc jack one.I'll post a gut shot as soon as I can scan it in.
The pcb's are not great quality that's for sure.

[Scruffie]

If your unit has the transformer in it then the pcb layout looks slightly  different to me from the dc jack one.
They may have moved it around. I can't tell clearly from the pictures I've seen.
It's definitely there on the dc jack one.I'll post a gut shot as soon as I can scan it in.
The pcb's are not great quality that's for sure.

No, vintage EHX PCB's tend to be a bit flimsy to work on, but hey, they've lasted 40-50 years so far!

I checked, 3 vintage units, none have that bit of circuit, I assume it's just a buffered reference voltage but why... and why was it added to later units but isn't on earlier ones (I have a schematic that doesn't show it dated 78, it's added by the time of the 79 schematic though).

I can only guess a part change (opamp brand perhaps, I recall some debugging posts by people that cloned the polyphase that had issues with some brands of opamps not working) meant it needed a slight redesign or that some units were not firing up after completion so it was added to stabilize the design.

[nik55]

Could it be related to the lack of transformer?
Does the mxr phaser  resemble  the polyphase at all?
http://halen.com/evh/index.php?name=PNphpBB2&file=printview&t=679914&start=0

[Scruffie]

Could it be related to the lack of transformer?
Does the mxr phaser  resemble  the polyphase at all?
http://halen.com/evh/index.php?name=PNphpBB2&file=printview&t=679914&start=0

That MXR phaser doesn't no, far as I know that version was never released as a production unit, it's a PWM phaser rather than FET or Optical.