good luck :3

hope it'll work in the end.

I now straightened all pins and added most of the missing components on the CPU-board. Soldered a socket for the 74LS02 but didnt have one in spare and ordered some. Also noticed the trimmer is damaged. Desoldered it and ordered a new one.

Today also my PC-10 III case with a matching PSU arrived:
Re: Bought these (retro) hardware today

Therefore that was a good chance to give it a 1st test without the need to add an AT-PSU-Adapter: Already looking very good!
- CLK is there.
- RST goes off after putting a 10 pF cap in the trigger mounting holes
- No display on post card but no surpise on a XT
- ...but 12V is missing.
Whats the reason? Now I noticed the VRM on the ISA/PSU board is missing, too. According to the manual it is a 7905. Will take a look if I find a card to take one from...shouldnt be required for operation.

Very helpful to have the circuit drawings available!

Next test will be with Supersoft and Speaker...

That sounds like great progress! Very happy to see this on the way back from butchering!

Btw., just in case you're looking for proper connectors for these Commodore (as I saw some extra connectors here: download/file.php?id=81042&mode=view) :
Mouser is still selling the proper plugs as 538-50-84-1060 (needing pins ordered separately). This is just because I had a PC10 PSU with an intermittend fault in the fully encapsulated transformer which made it unfixable for me and been looking for an alternative (ended up with a 12V ATX mini PSU and this plug).

Also hope you saw the bent pins on the underside auf the PSU/ISA board (on the ISA path)... 😀

Crossing my fingers for a quick fix now and thanks for updating this thread!

Hehe, indeed I mounted this extra connector on the PC10-III board for testing purposes. It was easy as the needed pins are on the top of the PCB. This is not the case for this board so I am happy to have the PSU available.

Good to know the connectors are still available, but the moment I dont need them. Price seems to be OK, maybe with my next order...

No, didnt notice notice the ISA-Pins so far 🙁 Thanks! Didnt have much time today and overlooked it as I focussed on the CPU-board...shit!

7905 is LM7905 regulator IC with 3 terminals. Drops -12V to -5V with some heat, used for ISA slots, audio card, serial ports and some specific cards use these -5V and -12V. For now, see if you -12V working first then install 7905 IC regulator.

Do you have -12V supply working from your PSU?

Cheers,

You are right, its the -5 V thats not working. I dont have a replacement but this doesnt matter at the moment.

Soldered a new trigger, straightened the forgotten Pins and powered on with a Supersoft-ROM, but nothing more happens. Reset goes off after part of a second, the other LEDs stay on. Hope this will change after installing the 74LS02 I am waiting for - dont know what this is needed for.

Yes get the 74LS02, make sure you are using correct one due to speed and LS, F etc?

Are you getting -12V? Is power good go active or go low or high certain delay after voltage comes on? May need dual input scope to check. Make sure clocks are running.

Some XT might be more advanced needs CMOS battery installed. Just throwing nuts out.

Cheers,

Yes, all other voltages are OK.

Yes I ordered 74LS02, exactly the one listed in the parts list.

Dont have a scope but my multimeter can measure the clocks. Lets wait until the 74LS02 arrives.

I managed to find a74LS02 on a scrap board. Desoldered and tested in the Commodore:

😀

Its alive! But no idea where to continue at the moment...

nice, grainy ^^

Thats how it currently looks like.

I tried different RAM configurations (4164/41256) to see if something in the RAM error pattern of Supersoft changes, but it stays the same.
Will take a closer look if there are shorts left (better do it with a photo...). Next I will check if all ICs get their supply voltage...

More suggestions are welcome 😉

Already found 1st candidate...

Just two things, which are hard to tell from the picture:
the capacitor over U14 - is it maybe touching other pins?
the ISA slot (JA/JB 11) - are the bent pins inside still separated or maybe touching?

Also, just for curiosity: what exactly are the remaining problems? Can't really tell much from the grainy picture 😁

Also, C74 might be shorted - at least looking from here....?

I will check this tomorrow, thanks!

I think the grainy picture itself is also a problem - that CGA card is not that bad in other PCs.
This is what the output looks like:
download/file.php?id=62587&mode=view
So the words with the grey background mean "failed": Timer, DMA, Memory.

If the CGA card happened to derive an (unstable) frequency from the MB, maybe that could result in such a picture? I have to admit - I haven't seen such a failure mode from a graphics card, yet, but do you have a frequency tester for the crystal near the timer IC (next to the CPU)?

Also, on the underside, in that area, there also is a connection that might be severed (by corrosion?) - at least it does look rusty exactly near the crystal's leg, if I am not mistaken?:

this is the missing -5V voltage regulator I assume?
what does that transistor T1 do there? maybe -5V is needed somewhere on the board after all, even though it seems to be on the input side?

I had funny issue with atom board once and it was missing voltage input from power supply on motherboard.

Please install 7905 regulator and see if that helps.

Cheers,

I checked all your observation, thanks for that!

MJay99:
- the capacitor over U14 - is it maybe touching other pins?
That one is totally OK

- the ISA slot (JA/JB 11) - are the bent pins inside still separated or maybe touching?
Also looks like that on the photo but is also OK. I inserted the POST card into that slot to prevent the pins are touching each other.

- Also, C74 might be shorted - at least looking from here....?
Indeed, this one was not looking good. I straightened the Pin.

- Also, on the underside, in that area, there also is a connection that might be severed (by corrosion?) - at least it does look rusty exactly near the crystal's leg, if I am not mistaken?:
I checked this one for connectivity and its OK.

imi:
this is the missing -5V voltage regulator I assume? what does that transistor T1 do there? maybe -5V is needed somewhere on the board after all, even though it seems to be on the input side?
Yes. thats the missing voltage regulator. For the T1...I dont have that much knowledge. You can see that part on page 18, bottom right, of the diagram
http://dostalgie.de/downloads/pc10-20-10II-20 … ODORE_EN_DE.pdf

I will now fix that broken trace on the bottom and expect it to have an effect. I will decide about ordering the regulator afterwards...

Thanks again! 😀