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Pet Dynamic Board UD5 ROM Question

Hugo Holden

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Dec 23, 2015
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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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daver2

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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
 

Hugo Holden

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Dec 23, 2015
Messages
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Location
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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
It confused me ! That is interesting, thanks, I will remove that ROM. before I try out the PCB.
 

daver2

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>>> 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
 

dave_m

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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.
 

Hugo Holden

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Joined
Dec 23, 2015
Messages
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Location
Australia
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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