MM5823N

What it’s all about...

A few years ago I bought a Polymoog ‘spares or repair’, confident in my ability to repair it and then play it for my own pleasure and that of others.

Unfortunately the MM5823N required for its repair, although used extensively in the 70s and 80s, ceased to be produced some time ago, thus rendering my Polymoog only good for spares.

Or so I thought.

Not being the type to give up easily, I managed to get a datasheet for the MM5823N and found that, whilst strangely it used negative supply, the actual divided outputs didn’t. This meant that it would be possible to use standard CMOS parts, which have equivalent supply voltages (just not negative ones) to make a replacement chip.

So I did.

Here’s a picture of the first one...made by my own fair hands and attached to the Polymoog divider board.

Then I realised that there might be other people out there wanting to repair their kit, so I redesigned the chip and can now offer it to you, any of you, for a small fee. It’s smaller and neater too!

It’s 18mm x 9mm in size which is the same footprint as a 14-pin dual in-line IC socket. That means it just solders in where the old chip went. It is assembled with one chip on each side, pins down - a neat two-chip solution to a problem of unavailability.