Wanted: Polymoog HFO board (ver. 2 only)

[Deleted]

Hello,
I'm after a Polymoog version 2 HFO board to go in the right-hand slot of the divider board on a 280A. Version 2 has a 4052 chip instead of a 4011 and is a different circuit. Can't use a version 1 in the right-hand slot on a 280A according to the service manual.

Please PM me if you have one you'd like to sell. Even if it's not working I'd still be interested (at a lower price of course ).

Thanks,
Barry.

[spoonz]

If you look at the Restoration pages for Shauns Poly on the main site you will see Shaun had a rev 1 and rev 2 Hfo in his Poly. I upgraded the rev 1 spec

My manuals are at work so i can't look at the moment to check the exact difference.

[Deleted]

That's interesting, thank you. I've looked at that restoration article several times and remember reading that. I had assumed you were referring to the stability updates (the extra resistors and the cap).

I've looked at the service manual schematics and they seem quite different boards, As a random example though, on version 1, pin 9 of the 7423 goes to pin 5 of the 7426. On version 2 it goes to pin 5 of the 4052.

EDIT: Just noticed you've edited your post, so I'm assuming again that you were referring to the service update mods that I've already done. Please let me know if I'm wrong.

Thanks again for your help,
Barry.

[spoonz]

The Rev2 board monitors an extra divider output for the phase lock loop. Depending on the manufacture date of the divider board this required a mod to link the extra divider output to the edge connecter. If the divider board doesn't have that mod then the rev2 board monitors the same outputs as a rev1. More an improvement rather than a necessity.

The mods to the rev1 were to bring the PLL stability up to Rev2 standards hence why i took that bit out as you mentioned having done that.

I might have an hfo at home. Will check later

[Deleted]

Interesting, when I had my divider board out I noticed it had a white wire soldered underneath between one of the divider chips and — I think — the edge connector. That sounds like it could be the mod you mention.

I might have an hfo at home. Will check later

That sounds good, I hope to hear from you. Is there any harm done if I use a version 1 temporarily while I fix all the other problems I'm likely to find?


Thanks for all your help,
Barry.

[spoonz]

Take a look at the pic of Shaun's Poly below. It was when he purchased it (pre hfo revision) and when i finished it, running a rev 1 card in the right hand slot.

To my knowledge it ain't blown up yet.

[Deleted]

Thanks! I'll give it a go then. I'm still interested in a version 2 though, so if you have one, please let me know.

EDIT: Hang on though, is that revision 1 or version 1, In other words, is it a 'revision 1' of a 'version 2' board? After all you said he had both version 1 and 2 boards in his Poly. I have 2 version 1 boards only, both updated to latest revision (by me). These boards came out of an early 203A as mine were missing when I bought it.

This is really confusing! I think I need a version 2 board no matter what revision. Does any of that make any kind of sense?

Thanks again,
Barry.

[spoonz]

Blimey your confusing me know

The board on the right in the pic is a Version 1. It was un revised originaly, i revised it. The left board is a revised version 2 (already done when he got it)

[Deleted]

Thanks for your help (is it Colin?), I appreciate it, but I have to stick to my guns on this one.

The manual mentions two versions of the HFO board, each has its own schematic diagram in the service manual (pdf pages 232 and 234) and are quite different. Even looking at the pictures of the boards shows how different the track layout is. I don't see how you can update one to the other. The service updates just, at most, add a couple of resistors and a cap to improve reliability/stability or whatever.

Most of all on page 232 of the PDF service manual (the version 1 schematic diagram) is states:

NOTE: This version not to be used as Sawtooth Rank No. 1 on Polymoog Keyboard

So, I think I still need a version 2 board (the one with a 4052 IC, not a 4011). If anyone has one please sent me a PM.

Thanks once again,
Barry.

[spoonz]

You are correct they are different, but i think you are a bit confused by revs and versions and what i'm saying (badly obviously) about why the difference is somewhat irrelevant.

There are only 2 boards full stop. Rev1 or version 1 is the same thing. Component wise quite different from the rev 2 but functionally identical apart from the exta pll line. In basic terms as long as what goes in and what comes out is the same, what happens inbetween matters not a jot to the function of the unit. They just did the same thing in a better way by using different components. Becaus ethe 4052 is 16 pin it required a board layout change.

The mods don't physically make a rev 1 into a rev 2 they just update it's stability to a level closer to that of the rev 2. The hfo design change was evolution rather than revolution. You can liken it to the faratron or moog psu. Both do the same thing but are totally different in design. If you mod the faratron it's almost as good as the moog and that is the same scenario for the hfo designs.

any clearer ?

If i had a rev1 or rev2 in my hand i would fit the rev2 but i wouldn't lose any sleep over it if i only had a rev1

[Deleted]

Hello spoonz,

There are only 2 boards full stop. Rev1 or version 1 is the same thing.

Okay, that's where the confusion came in. I'm just going by the service manual which refers to 'version' as the completely different boards using the different chip and 'revision' as the stability/reliability updates that they introduced to those boards.

E.G. page 232 of the PDF has a list of revisions to version 1 (A-L), while page 233 has a list of revisions to version 2 (A-C).

Anyway, that's cleared that up I think. What worries me about trying version 1 in the sawtooth rank is that warning I posted in my previous post: "...not to be used..." is quite a strong warning! I just don't want to damage anything after all the time and money I've spent on it so far. I'd hate to fry the rare and expensive 50240 IC for example.

Maybe I'll pluck up the courage to try it tomorrow and see.

Thanks a lot for your help, I do appreciate it.
Barry.

[spoonz]

It's a note rather than a warning in my manual.
Polymoog manuals are riddled with inaccuracies. For example the 203a from serial 3900 onwards uses the same rev2 hfo's and divider board with mod as the 280a but the note doesn't mention not using a rev1 in a late 203a. In this case the note is not likely a mistake they just ommitted the 203a from the note.

As to why they include the note, i can only guess at the meaning. It's a backward step stability wise to use a Rev1 board. The whole point of the Rev2 board and divider mod was a stability update, something they were obsessed with on the Polymoog due to it's reputation. To stop a tech fitting a rev1 card and undoing their work they include the note. whether the stability mods were around for the rev 1 at the time of the manual being written i am not sure. The manual has the revision introduction serial numbers so i can check.

If you are at all concerned hold out for a rev 2. All i can only say is that i have used both in 280a's without issue and the circuit diagram doesn't show me any reason why it would be an issue. The service notes in the manual were written by Don Besecker so you could email him for an opinion. He runs DBM electrical in NY Usa

[Deleted]

Thanks, that makes sense that they want to avoid a tech doing a backwards step. I've found a couple of strange things in the service manual myself already, like a resistor designation being listed twice with two different resistor values.

Anyway, I think you've convinced me, I'll give it a try tomorrow hopefully. I'm pretty sure it's not going to spring into life anyway, I think I've only just started on the fault finding mission with this one!

Thanks again,
Barry.

[brassteacher]

Barry, I can confirm the Rev. 1 card will work in the slot that the service manual says "Don't do that". I was standing behind the synth one time when I put the cards in, and put them in backwards. I switched them back when I figured it out two days later.

As to there being only two cards, I've seen photos of two Rev.1 boards where the board artwork was clearly different. Cleaning up stray capacitances perhaps...

[Deleted]

Hello Don,
Thanks for that, I'm definitely going to try it later today if I can.

One reason for changing the track layout from what I've seen is to accommodate the extra components added for the stability/reliability updates. I.E. the 10k and 1M resistors and the 2.5pF tantalum capacitor. Mine are early boards as you know, but I've done the updates to them both.

I'll update my "restoration" thread with the results of my testing.

Thanks again,
Barry.

[spoonz]

Jun 9, 2011 2:35:20 GMT brassteacher said:

As to there being only two cards, I've seen photos of two Rev.1 boards where the board artwork was clearly different. Cleaning up stray capacitances perhaps...

Both the Rev1 cards i saw looked the same but i didn't scrutinise them that closely. It wouldn't suprise me if some of the mods that are add ons for early cards got incorporated into the build as production went on. But essentially 2 design wise with some revs along the way

I have 2 TL boards here and 1 has external updates added mostly by me and the other has most of them incorporated into the board itself. The schematics do list some build revisons for various boards. Most saw some change over time.

All adds to the fun