Re: [AH] Farfisa Syntorchestra TOS weirdness

From Ben Bradley
Sent Sat, Nov 3rd 2018, 00:33

From what you describe it does sound like the AY-1-0212 could be the
problem, but I just found this thread, and I'd suggest doing post #2
before anything else:

https://www.organforum.com/forums/showthread.php?50711-Help-needed-with-a-F=
arfisa-Syntorchestra-tms3839-sn29858

I've gone trough a few Lowery organs, the top octave chips that I've
seen from them are MK50240,  Looking at the datasheets, the pinouts
are kind-of the same, but the 50240 runs on 11 to 16V and the
AY-1-0212 has TWO supply pins, one with a range of 24 to 27V, the
other 12 to 15V. Offhand it looks like the AT-1-0212 is the older
chip, as they tended to need several voltages for power.

I hadn't heard of the AT-1-0212 chip, I'm only familiar with the
MK50240 and MK50241 (these were available at Radio Shack in the USA
circa late 70s), but it appears there were many manufacturers of such
chips (of likely varying compatibility), as listed here:
https://www.musiker-board.de/threads/der-begriff-hammond-orgel-und-seine-ge=
schichte.529178/
On Fri, Nov 2, 2018 at 3:59 PM Murray <xxxxxxx@xxxxxxxxxxxx.xxx> wrote:
>
> That is a terrible way to draw logic chips. I have a few TOCs from around=
 that era mostly from Lowery organs but as I do not have any Lowery organ s=
chematics so I cannot confirm the pin outs. Yes they do get warm which is o=
ne reason why they fail and if there is room a small heat sink glued onto t=
he chip is not a totally silly idea with these.
>
> If you are saying that when the clock is doubled the TOC then behaves cor=
rectly then that is perplexing. Maybe you could alter the Mono/Poly clock s=
ystem to always run at the Poly speed.
>
> MH
>
>
> On 3/11/2018 5:09 AM, Travis Thatcher wrote:
>
> I've been having some trouble with a Farfisa Syntorchestra and i suspect =
its the AY-1-0212 top octave gen. but I want to be sure before I go about t=
rying to find a replacement. Currently once the synth warms up the E, F# an=
d sometimes G# notes crackle or do not play at all when in Trombone setting=
 on the poly synth side. I scoped the pins of the AY-1-0212 and I can see t=
he fluctuation on the square waves of the offending voices. even with the d=
ividers removed. The 0212 does get warm and I'm not sure if this is normal =
- not to hot to touch but warm. I've gone over the solder connections and a=
ctually replaced with wires for the pin of the 0212 responsible for F# to t=
he divider chip. The weird thing is that with the other poly switches every=
thing works just fine - the divider seems to bump up an octave for those ot=
hers, judging by the waveforms.
>
> I have: replaced the socket for the 0212, the sn7400 quad nand, tried a d=
ifferent divider and replaced its socket.
>
> This is the GIE version, here's the service man: http://maxforcats.com/wp=
-content/uploads/2014/08/Farfisa-Syntorchestra-Schematics.pdf
>
> I'm stumped and would love some guidance if anyone has familiarity with t=
hese. Also, if anyone has an AY-1-0212 TOS for sale i'd be interested in bu=
ying if indeed that turns out to be the case. I do have another working syn=
torchestra that I can take apart and swap TOS chips if it is also a GIE ver=
sion. I'll look into that this weekend.
>
> Thanks!
>
> --
> http://www.travisthatcher.com
> http://www.soundcloud.com/thevoiceofsaturn
>
>