Paia 2700/4700 regulated power solution

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eveready9v
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Paia 2700/4700 regulated power solution

Post by eveready9v » Fri Mar 20, 2020 12:58 pm

Hi there,
Since being quarantined in the house with corona-virus on the loose I'm trying to tie up project loose ends, one of which being an old Paia 2700/4700 that I scored years ago. It has the old unregulated power supply, and I've never come across the 4771 regulated power supply for sale on the used market, so I'm finally going to try and cobble something together to get this old girl up to speed. Wanted to see if anyone had a recommendation of what to use to get it together, as I know that Paia has some funky powering. Hoping I can order parts from the world while its still delivering. Any help would be greatly appreciated.
Thanks
Barry

Rob_C
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Re: Paia 2700/4700 regulated power solution

Post by Rob_C » Fri Mar 20, 2020 8:21 pm

There are many ways to approach this, if you want to throw some money at it, here is a dual output PSU kit from Jameco:

Link-> Dual-Output Adjustable Linear Regulated Power Supply Kit

This is the same kit Blacet used to recommend if you didn't have a good PSU on hand and needed something to power a few Blacet modules. The mains connects to the PCB and is exposed, so be sure to insulate that properly. Or don't, just like PAIA!

Otherwise, the MFOS wall wart supply will work well and is safer. Link->MFOS power supplies at Synthcube

EDIT: These options provide plus and minus nine volts (bipolar) but you will need an additional source for the eighteen volts.

Dave Brown's PAIA restorations on ModularSynthesis.com "Synthesizer Restoration and Builds" has very helpful information and shows his approach for the construction of a PSU.
Last edited by Rob_C on Sun Mar 22, 2020 11:30 pm, edited 1 time in total.

KSS
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Re: Paia 2700/4700 regulated power solution

Post by KSS » Sun Mar 22, 2020 3:53 pm

The 4771 18V rail isn't regulated. Better to use another PSU design for that part. The 7805 based - and + parts work great and wouldn't be hard to DIY.

Even a simple 7809, 7909, 7818 based PSU will suffice if you can still find 78xx in these now not so common values.

I wouldn't use or suggest an MFOS style WW halfwave supply. 4700 really benefit from clean, stable power.

Beef up the caps on the ++ 18V module inputs.

Rob_C
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Re: Paia 2700/4700 regulated power solution

Post by Rob_C » Sun Mar 29, 2020 7:55 pm

KSS wrote:
Sun Mar 22, 2020 3:53 pm
I wouldn't use or suggest an MFOS style WW halfwave supply. 4700 really benefit from clean, stable power.
Ok. Then build the "MFOS Adjustable LM317/LM337" power supply shown on that same page instead of the "MFOS Wall Wart Bipolar" power supply. The adjustable supply uses a center tapped transformer instead of a wall wart.

Here is the schematic if you want to DIY it as suggested by KSS. It puts out +18, +9 and -9 volts. If you want a bare bones supply just build the top part. The bias supplies and capacitor patching are on the bottom.

Yes, those are five volt regulators in the schematic.

4771 A.png
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KSS
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Re: Paia 2700/4700 regulated power solution

Post by KSS » Sun Mar 29, 2020 9:21 pm

Rob_C wrote:
Sun Mar 29, 2020 7:55 pm
Yes, those are five volt regulators in the schematic.
Another cool John Simonton 'hack' that is good to keep in mind as 78xx in older less-used and so strange values disappear.

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