[sdiy] A20G545 chip, what is it?

grant musictechnologiesgroup.com grant at musictechnologiesgroup.com
Mon Jun 20 00:57:49 CEST 2022


I was thinking that too. SSM came from Exar, non? I seem to recall Exar having some pretty sad looking silkscreening.


------ Original Message ------
From: "Nathan Trites" <nathan at idmclassics.net<mailto:nathan at idmclassics.net>>
To: "John Speth" <johnspeth at yahoo.com<mailto:johnspeth at yahoo.com>>
Cc: "SDIY" <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Sent: 6/19/2022 11:57:32 AM
Subject: Re: [sdiy] A20G545 chip, what is it?

There certainly are pictures of plastic SSM ICs with similar datecode lines and lettering just as wonky so that could be it...
https://www.ebay.com/itm/192742272128
https://picclick.com/SSM2033-VCO-chip-NOS-Korg-MP4-Monopoly-etc-332999604291.html

Nathan

On Sun, Jun 19, 2022 at 10:54 AM John Speth via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>> wrote:
I don't think it was an LM389 (audio power amp) but that got me thinking: Could it be a mismarked SSM2033? The pin count matches and the power connections (the only connections wired) are consistent with the data sheet. Sometimes shipments to manufacturers are marked according to the buyer's specs (obfuscation, custom variation, etc). I can't remember from whom I was buying my small quantity SSM chips at the time. There were not a lot of retail mail order sellers back then. - JJS

On Sunday, June 19, 2022, 07:14:38 AM PDT, Mike Bryant <mbryant at futurehorizons.com<mailto:mbryant at futurehorizons.com>> wrote:



Possibly an LM389 transistor array equivalent





From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>] On Behalf Of John Speth via Synth-diy
Sent: 19 June 2022 14:58
To: SDIY
Subject: Re: [sdiy] A20G545 chip, what is it?



Photo at: https://myplace.frontier.com/~jspeth/A20G545.JPG



I should have posted this pic first. The date code accurately indicates when I built it: 1983. So anything with origins past that date are not valid.



Thanks - JJS



On Sunday, June 19, 2022, 06:05:02 AM PDT, <synth1 at airmail.net<mailto:synth1 at airmail.net>> wrote:





I'm pretty good at this if I can SEE a photo.

Paul S.

-----Original Message-----
From: Synth-diy <synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>> On Behalf Of brianw
Sent: Sunday, June 19, 2022 3:16 AM
To: John Speth <johnspeth at yahoo.com<mailto:johnspeth at yahoo.com>>
Cc: SDIY <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Subject: Re: [sdiy] A20G545 chip, what is it?

My first guess was a 74x545 octal bidirectional transceiver, non-inverting.
They're 20-pin.

However, that doesn't seem to fit on a SSM voice card (or into an 18-pin
package).

Brian


On Jun 18, 2022, at 7:59 PM, John Speth wrote:
> Today I was dumping old circuit boards that I built many years ago. I was
stripping valuable parts from one and I found two 18 pin DIPs that are
marked "A20G545" on one line and "MCE 8211" on the line below it. 8211 is
the date code (1982). The other markings are a mystery. Searching for this
chip online was a dead end for me. Does anybody know what it could be? It
was from a board that contained an SSM 2012 VCA and an SSM 2044 VCF. I've
lost the schematics. It was my design.
>
> Thanks - JJS



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