Posted By
Retroshire
on 2025-11-03
10:34:52
|  Measuring continuity U5 en U6 RAM's
Catastrophic attempt to expand a Commodore 16 with 64kb, did it a thousend times, but this one is horror.
I lost 3 tracks and 3 other contactpads: visually observerd: I lost only on the above side of the board pads of pin 2 (d0), 3( d1), 5 (RAS) and 14 (a0), I lost 3 tracks also only on the above side of the board: between pin 5, 8, 14 (made already a patch between them).
My question: when measuring U6 and U5, should there be continuity on all parallel 18 pins (u5 pin 1 and u6 pin 1 etc etc) ?
Referring the schematics its looks that way, but I want to be sure not to lay a patch between legs that don't need it.
At this moment I don't measure continuity between U5 and U6 on pins: 2, 3, 15, 17
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Posted By
Verona
on 2025-11-03
12:01:07
| Re: Measuring continuity U5 en U6 RAM's
By the way, how interesting that I finished my Memtest program on Plus4 yesterday and here we have a RAM problem too. 
When the problem is solved and it's time to test the RAM, let me know and I'll give it to you. Unless I have time to post it here before then.
Here it is: Memtest Plus/4
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Posted By
siz
on 2025-11-03
15:07:05
| Re: Measuring continuity U5 en U6 RAM's
As far as I remember (it's been a long time since I've looked at C16 schematics) all the pins should be connected except the data lines (pins 2, 3, 15, 17) which means You should be good.
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Posted By
SukkoPera
on 2025-11-03
15:20:13
| Re: Measuring continuity U5 en U6 RAM's
To check these things, you can use the LittleSixteen project. In particular, the schematics from V2 should match the original board 100% and should be rather clearer than the original ones you can find around. If you download the V2 KiCad project, you can also highlight and follow every track on the PCB pretty closesly. That's one goal of the project and I find it rather useful for repairs.
Also, my Fixteen project can do the 64 kB upgrade in a cleaner (and not really more expensive) way. But then, why not go straight to 256 kB or 512 kB? 
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