Expanding MoonSound sample RAM

Master (245)

15-10-2022, 13:03

Today I received two HITACHI HM628512LP-7 DIP-32 524288-word x 8-bit High Speed chips I ordered from Ebay (https://www.ebay.com/itm/401706327631) to replace two RAM chips in my MoonSound. Putting them in was easy enough, but now I need to set some jumpers, that I can't find.

Can anybody tell me how to proceed?

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By sdsnatcher73

Prophet (3951)

15-10-2022, 13:19

It’s written on the board, J2 needs to be 1-2. J3 and J4 need to be 2-3. The jumpers are pre-wired on install, remove that and install pin headers.

By Wlcracks

Hero (565)

15-10-2022, 13:46

I cannot see it on the picture due to the low resolution, but it could be the jumper is set with the tracks, so you could have to cut the trace. Looking at the table printed on the board, the jumper is "right" or "left".

By The Apeman

Master (245)

15-10-2022, 13:54

Thanks

- J2 seems to be three holes, two of which are connected at the back by solder. Is that what I should remove?
- Same for J3 and J4. If they are pre-wired as indicated for 128K (1-2), than I assume they're are numbered towards the edge. Correct?

By Wlcracks

Hero (565)

15-10-2022, 13:58

Yes remove it always, it cannot have two logic states. This COULD malfunction the unit. Sjaaq has this 2.0 unit I guess, if you have some patience maybe he can verify this on this moon sound. I don't have it here atm.

By The Apeman

Master (245)

15-10-2022, 14:00

Right. You mean if I install the headers SDSnatcher suggested and leave the pre-wiring intact it could malfunction, or even if I do as SDSnatcher says? I'd hate to brick my MoonSound.

By SjaaQ

Champion (375)

15-10-2022, 15:19

I think we just removed the pre-wired link and soldered in real jumpers:

This is the v2 I currently got. It is configured for 1MB, but now only has 512K.

By sdsnatcher73

Prophet (3951)

15-10-2022, 15:22

I think if you remove the solder from the jumper pads and install the headers it should be fine. You can verify by testing continuity on the 3 pins, with no jumper installed there should (obviously) be no continuity. If there is you have to check how the connection is created and remove it. Don’t power the MoonSound with continuity on both 1-2 AND 2-3, like wicracks mentioned.

Ah SJAAQ beat me to it by 2 mins…

By The Apeman

Master (245)

15-10-2022, 15:31

Nice. I do have a lot of rows of male headers, but where can I buy those blue (?) pins to connect the right ones?

By sdsnatcher73

Prophet (3951)

15-10-2022, 15:35

Here for instance.

By The Apeman

Master (245)

15-10-2022, 15:41

Nice, thanks!