Cartridge slot expansion board

[Amon_RA]

Hi All,

I found this old home-made cartridge port expansion board.
I can only get the 1st slot closest to the VIC20 working, but I have no idea how the other slots are supposed to be used...

Does someone have experience with this kind of expansion board that can provide more info?
There are no switches so I'm a bit clueless...

[chysn]

From the picture of the bottom side, it looks like there's at least one trace that's broken, on the end between the first and second slots. Some others look questionable, but that could be lighting. Do you have meter to test continuity?

[Mike]

[...] it looks like there's at least one trace that's broken, [...]

That's the +5 VDC supply rail. That trace is not really broken, it looks more like vapourized due to excessive current at some instance.

The circuitry is supposed to make +5 VDC from 9 VAC. It is possible this supply made a short with in the internal +5 VDC of the VIC-20, and thus blew the unsuspecting trace like a fuse. There's a group of 4 open solder eyes visible in the top right of the upper photo, which probably were wired to a switch, so that part supposedly has been taken out of function anyway.

At least all those 10 MegOhm resistors are not going to do any harm. Not that the VIC-20 expansion bus would require any termination - but it's a funny method to add vias.

I have no idea how the other slots are supposed to be used...

As long as cartridges do not use conflicting memory areas, they can be operated in parallel. Like a VIC-1111 (+16K in BLK1 and BLK2), a VIC-1110 switched to BLK3 and another VIC-1110 switched to BLK5 will give +32K RAM in total, of which +24K RAM are usable by BASIC. The +8K in BLK5 do not form a continuous range with the rest of the RAM expansion and thus don't add to the BYTES FREE in the start-up prompt, but still could be used to soft-load cartridge images.

[DarwinNE]

I was wondering the purpose of the 10 Meg resistors, apart being used as vias Bleeding electrostatic charges?

Apart from that, I have a three-slot mini motherboard extension for my VIC (without the 7805 circuit, but with a much better PCB). I find it useful as I have two 16K memory expansions that I configured to be used together as a 32K expansion.

Solutions like those were common, here is an article of an Italian magazine (MC Microcomputer 16, February 1983) that proposed one as a kit:

http://www.digitanto.it/mc-online/PDF/A ... _045_0.pdf

The same article is available here (where it can be translated with Google or other similar solutions):

http://www.digitanto.it/Articoli/VIC-20_03.htm

[Amon_RA]

From the picture of the bottom side, it looks like there's at least one trace that's broken, on the end between the first and second slots. Some others look questionable, but that could be lighting. Do you have meter to test continuity?

Thanks! I fixed the trace and tested coninuity for everything else. All slots are working now!

That's the +5 VDC supply rail. That trace is not really broken, it looks more like vapourized due to excessive current at some instance.

The circuitry is supposed to make +5 VDC from 9 VAC. It is possible this supply made a short with in the internal +5 VDC of the VIC-20, and thus blew the unsuspecting trace like a fuse. There's a group of 4 open solder eyes visible in the top right of the upper photo, which probably were wired to a switch, so that part supposedly has been taken out of function anyway.

What would the purpose of such a circuitry be?

As long as cartridges do not use conflicting memory areas, they can be operated in parallel. Like a VIC-1111 (+16K in BLK1 and BLK2), a VIC-1110 switched to BLK3 and another VIC-1110 switched to BLK5 will give +32K RAM in total, of which +24K RAM are usable by BASIC. The +8K in BLK5 do not form a continuous range with the rest of the RAM expansion and thus don't add to the BYTES FREE in the start-up prompt, but still could be used to soft-load cartridge images.

Thanks for the information! Makes sense

[Amon_RA]

I was wondering the purpose of the 10 Meg resistors, apart being used as vias Bleeding electrostatic charges?

Apart from that, I have a three-slot mini motherboard extension for my VIC (without the 7805 circuit, but with a much better PCB). I find it useful as I have two 16K memory expansions that I configured to be used together as a 32K expansion.

Solutions like those were common, here is an article of an Italian magazine (MC Microcomputer 16, February 1983) that proposed one as a kit:

http://www.digitanto.it/mc-online/PDF/A ... _045_0.pdf

The same article is available here (where it can be translated with Google or other similar solutions):

http://www.digitanto.it/Articoli/VIC-20_03.htm

Thank you for the info and very interesting links!

[Mike]

What would the purpose of such a circuitry be?

It's there to provide an auxiliary power supply when more than one cartridge is operated.

The example I gave above would sport 16 2Kx8 6116 SRAMs to provide the +32K RAM expansion. Each of the SRAMs takes around 30..60 mA, so that would amount to an extra ~1 A taken from the PSU. No good idea with the original "Wedge" type power supply ...