[sdiy] SCI Six-Trak

[Steve Lenham]

----- Original Message ----- 
From: "mark verbos" <mverbos at earthlink.net>

> Does anyone know what the story with revisions of this is? I have  fixed 3 
> of them that all had green PCBs and matched the schematic I  downloaded. 
> The one I'm looking at now has a blue PCB and a bunch of  green wires 
> modding it on the solder side. It has no U123 installed.

I think what you have there is a Rev.A board. I have one too; most of the 
same ICs are present but, as you found, they are all numbered differently. I 
haven't seen a schematic for the Rev.A. It just makes faultfinding more 
fun - mine had a stuck bit on the DAC which made it behave very strangely.

IIRC, the Rev.A uses the reviled MM5xxx noise generator IC rather than the 
noise transistor found in later Revs. According to NoteIt 
(http://www.geocities.com/SoHo/2163/sc.html), serial numbers up to 900 were 
Rev.As.

> There's just a "3" on the screen all the time.

I think the Sixtrak autotunes at power-up and counts through the six voices, 
so that might indicate a problem with voice 3. Does swapping CEM3394s in the 
voices change the number?

> It could be the EPROM, but I don't have a schemtic that matches and  now 
> I'm lost.

If you decide to replace/reprogram the EPROM, be aware that the Rev.A 
requires an earlier version of the firmware (v0.9), not the latest. It can 
be downloaded from NoteIt's site as above.

> Anyone?

Yes, me. Hope it helps!

Cheers,

Steve L.