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Pet Dynamic Board UD5 ROM Question

Hugo Holden

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Since I suffer from a spare parts disease, I saw a dynamic PET board on ebay, just like the one in my recently acquired PET, so I thought I would buy it as a spare.

Oddly because my original PET board had no hardware faults and I did not have a fault to sort out and repair. I find if I have a faulty board, I learn a lot more about it trying to diagnose and repair a fault. Seems odd but that is the way I learn about some designs.

So I bought this similar board, in the hopes that it might actually have a fault I could get to repair. I have not tried it yet.

This one has the extra bank of memory chips installed, hand soldered, no sockets, so I assume like my original board, it has the upgrade to 32k memory.

It has all original MOS ROMs it appears:

UD9= 901465-03
UD8= 901474-01
UD7= 901465-02
UD6 = 901465-01
UD5 = 901447-29

The thing is my original PET board did not have any IC installed for UD5.

What does the UD5 ROM do ?
 

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>>> What does the UD5 ROM do ?

The answer is nothing!

The 901447-29 ROM is the "Screen editor for BASIC 4, normal keyboard, no CRTC (40 columns)" (i.e. it should live in socket UD8 not UD5 and is for a different version of BASIC).

I suspect someone has stuffed this ROM into this socket to confuse someone...

If you don't already know, you can look up 99% of the ROMs here: http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html

Dave
 
>>> What does the UD5 ROM do ?

The answer is nothing!

The 901447-29 ROM is the "Screen editor for BASIC 4, normal keyboard, no CRTC (40 columns)" (i.e. it should live in socket UD8 not UD5 and is for a different version of BASIC).

I suspect someone has stuffed this ROM into this socket to confuse someone...

If you don't already know, you can look up 99% of the ROMs here: http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/index.html

Dave
It confused me ! That is interesting, thanks, I will remove that ROM. before I try out the PCB.
 
>>> I will remove that ROM. before I try out the PCB.

It is definitely not required for BASIC 2 - but BASIC 2 should still work OK with it in position.

Dave
 
All the big chips are socketed. That is good news and bad news. It is very helpful when troubleshooting a broken board, but those sockets can cause connection problems over time. Are you considering using some contact cleaner on those sockets? it may be a good idea if your board does not come up. Certainly you should rock the chips in the sockets to rub off the oxide.

I can't get over how good your board looks. Someone took good care of it.
 
All the big chips are socketed. That is good news and bad news. It is very helpful when troubleshooting a broken board, but those sockets can cause connection problems over time. Are you considering using some contact cleaner on those sockets? it may be a good idea if your board does not come up. Certainly you should rock the chips in the sockets to rub off the oxide.

I can't get over how good your board looks. Someone took good care of it.
I have standard protocol where before even testing the board I remove the socket IC's and clean the oxides off the pins,also I test each socket pin for tension with a test pin and I also lubricate all of the pins and sockets with Inox's mx-3 this way I don't run into bad socket connection issues.
It does seem to be a remarkably clean board.
 
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