cartridge on/off switch

[+Larry]

Finally got around to this today...

 

On my 16K eprom cart, both pins 13 and 14 (+5V and RD5 respectively) are tied together all the way to the top of the cart (one big 1/8" trace). So cutting one will cut both. Does that pose any complication, or should be OK to cut (both) and attach the switch?

 

-Larry

[Rybags]

Probably - the +5V is needed by cart to supply power to the ROM and any other ICs.

 

Dremel with thin grinding wheel is a good way to seperate the two, then just solder to the RD5 in a place where it won't interfere with insertion of the cart.

[+Larry]

Thanks, Rybags.

 

Ok, I'd separate the trace maybe 1/2" up from the contacts and then cut RD5 in that area and add the switch wire.

 

But (out of curiosity) what happens if I just cut through the combined trace and effectively cut the power (and RD5) with the switch? Would this cause some type of "unintended consequences?" (Clearly easier, but...)

 

-Larry

 

 

 

Probably - the +5V is needed by cart to supply power to the ROM and any other ICs.

 

Dremel with thin grinding wheel is a good way to seperate the two, then just solder to the RD5 in a place where it won't interfere with insertion of the cart.

[Rybags]

I'd say the ROM would register as being present but wouldn't be able to be read and you'd end up with a 32 or 40K machine situation and it'd just boot the disk or goto Self-Test.

[+bob1200xl]

Can you post a picture, Larry? What kind of cart are you working with?

 

Bob

 

Thanks, Rybags.

 

Ok, I'd separate the trace maybe 1/2" up from the contacts and then cut RD5 in that area and add the switch wire.

 

But (out of curiosity) what happens if I just cut through the combined trace and effectively cut the power (and RD5) with the switch? Would this cause some type of "unintended consequences?" (Clearly easier, but...)

 

-Larry

 

 

 

Probably - the +5V is needed by cart to supply power to the ROM and any other ICs.

 

Dremel with thin grinding wheel is a good way to seperate the two, then just solder to the RD5 in a place where it won't interfere with insertion of the cart.

[+bob1200xl]

Having an un-powered chip on the bus is not a good plan... Even if it works powered off, switching it on may 'glitch' the address or data bus.

 

Bob

 

 

 

 

 

Thanks, Rybags.

 

Ok, I'd separate the trace maybe 1/2" up from the contacts and then cut RD5 in that area and add the switch wire.

 

But (out of curiosity) what happens if I just cut through the combined trace and effectively cut the power (and RD5) with the switch? Would this cause some type of "unintended consequences?" (Clearly easier, but...)

 

-Larry

 

 

 

Probably - the +5V is needed by cart to supply power to the ROM and any other ICs.

 

Dremel with thin grinding wheel is a good way to seperate the two, then just solder to the RD5 in a place where it won't interfere with insertion of the cart.

[+Larry]

Hi Bob, Gary-

 

Here's a picture of the cart -- a nice 16K DEICO from about 1985. Contact 15 is missing; and 13/14 joined as I mentioned. My current plan is to cut the short, lower angled section of the joined trace between the two and then attach the switch wiring on the (separated) pin 14. I have lots of Dremel cutters so this should go pretty well.

 

I found a Q&D way to simulate cutting both traces. I took a piece of "Magic Tape" and covered the +5V and RD5 to simulate cutting both. Then internal BASIC takes over on booting. But understand about "not a good plan."

 

Edit: actually it looks like it might be possible to separate the trace right above the connector. Then the bottom wire connection can go at the top of the cart connection and the upper wire can go anywhere on the trace above the cut (and still get the necessary +5V).

 

-Larry

[+Larry]

Here's the finished cart. Fairly uneventful. The SP-ST micro-mini switch fit with just a bit of room to spare. Switch is insulated with a small piece of electrical tape. Had to trim the legs of the socket underside just a bit so that the pcb would lay flat in the shell. Works great. I would have preferred to mount the switch on top, but the sidewall at the top is much thicker, so the side had to do. It is difficult to see, but I did cut RD5 just above the cart contact and had plenty of room to attach the wire.

 

Cart ON gives cart

Cart OFF (no OPTION) gives BASIC

Cart OFF (OPTION) gives Dos + 48K

 

Thanks Marius, Gary, and Bob!

 

-Larry

[Mr Robot]

What happens if you just cut the +5v line and put a switch there?

[1050]

Not trying to pick on you here, but that's exactly

what Larry did do...

 

So are you talking about removing power for the cartridge

from the computer motherboard instead?

 

Because I have an 800 that does that and it's a very

handy way to turn on BASIC for example if that is the

cartridge in the slot. Flip the switch and hit RESET

and BASIC is either there or it's gone depending the

switch setting.

 

I didn't know what the switch did when I saw it underneath,

you can access with the left hand to deftly work it

while to anyone not knowing it was there, it's magic.

 

I flicked it with power on and my screen tore up, so

then hit RESET which appropriates the display list

properly again and I see BASIC. So I must have a

BASIC cartridge plugged in then? And yes, I do.

 

Doing this on XL/XE will lead to a lock up. So pressing

RESET then will cause a coldstart to happen, but aside

from those drawbacks this will work there too.

[Mr Robot]

Thats not what Larry did. He cut the bridge between +5v and RD5, 5v is still present on the rest of the cart.