CBM PET 8296-D KEYBOARD PROBLEMS

[Desperado]

Good evening guys, i'm here again....i'm not a lucky guy with this vintage computers
I receveid 8296-d pcb from my friend (he repaired some track), now seems to works correctly but some keyboard s' keys they don't match with that i can see on screen. Most part of letters and numbers are ok but if i press some symbols or some keys (inst del or crsr) don't match!
I have this keyboard (picture) and this current version of edit rom (ue8): 324343-03.

Thanks so much for any help

 

[daver2]

So, first things first, the schematics are here for the keyboard interface: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/8296/324644-3of9.gif.

UE2 (PA0-3) provide the signals for UE1. This decodes for one set of keys.

The keys come back into UE2 Port B (PBx) and have pull-up resistors on each line.

With NO KEYS pressed on the keyboard - use your logic probe on pins 10 through 17 of UE2 (6520). These lines should all be HIGH and NO PULSING (indicating that no key is accidentally shorted).

Try that first.

Dave

 

[Desperado]

Thanks my friend! I ll try this tomorrow! Have a good night!

 

[daver2]

And you!

Dave

 

[Desperado]

Good morning!
I tested UE2 (pins 10 to 17) with logic probe, i have HIGH signal on every pin!

Can be wrong edit rom versione maybe?

 

[Desperado]

unfortunately I also broke the key that closes the door of a drive,is it possible to find one somewhere?

 

[daver2]

Good morning!
I tested UE2 (pins 10 to 17) with logic probe, i have HIGH signal on every pin!

Can be wrong edit rom versione maybe?

You are supposed to have a HIGH on every pin , so I was expecting this...

I’ll give you the next test after I have had lunch.

>>> Can be wrong edit rom versione maybe?

What language keyboard have you got, and what EDIT ROM is installed?

Dave

 

[Desperado]

You are supposed to have a HIGH on every pin , so I was expecting this...

I’ll give you the next test after I have had lunch.

>>> Can be wrong edit rom versione maybe?

What language keyboard have you got, and what EDIT ROM is installed?

Dave

Dave, i solved problem!
I burn another editor rom with this version : 324243-02b and now all keys match!
Unfortunately, i tested the two drive with a floppy, i launched directory command, i heard drive moving but i can't see
directory

 

[Desperado]

I have this message when i try format a disk:

 

[daver2]

I assume this is a different drive to the one that we repaired recently?

Since some of your previous problems were associated with the floppy disk media that time (after passing the POST) shall we start there this time?

What media are you using with the 8296-D drive?

Dave

 

[Desperado]

I assume this is a different drive to the one that we repaired recently?

Since some of your previous problems were associated with the floppy disk media that time (after passing the POST) shall we start there this time?

What media are you using with the 8296-D drive?

Dave

Yes, this is 8250 dual drive integrated in 8296-d cbm pet!
I used same type od disk, 3M DS,DD...

 

[Desperado]

I know I am repetitive but I have seen that it brings luck to write it ...I'm desperate!

 

[daver2]

I am just wondering whether these should be double sided quad density?

Are they marked as 96 tpi by any chance (tracks per inch)?

I am trying to find some info on the disk drives themselves. Can you identify the manufacturer, make and model number of the actual disk drive?

Dave

 

[Desperado]

Good evening Sir, floppy is this in picture....for the disk drives instead I have to figure out how to take them apart...

I've never disassembled an 8296 and I need to figure out how to do it

 

[daver2]

I had a bit of time at the end of a meeting to research the type of disk drives in the 8296 and came across this interesting text at https://www.oldcomputr.com/commodore-8296-d-1984/:

>>> the drives in the 8296-D use the uncommon quad-density disks, like the 8250 and 1001. I have used double density disks for some tests and they worked fine.

Another website at http://www.computinghistory.org.uk/det/31789/Commodore-Pet-8296-D/ refers to:

>>> ... were sold as 8296 or, with a built-in 8250 dual disk drive, as 8296-D.
>>> The top of the line Commodore Pet 8296D computer with integrated 8250 high density drives.

You 'may' be OK with DS/DD disks - but (if they are old) you may not be lucky.

You may need to look around for some QD or HD disks - or keep trying DS/DD disks until you find one that works...

However, this website: http://www.primrosebank.net/computers/pet/documents/8050_8250_service_manual.pdf clearly indicates that the disks for the 8250 should be DS/DD?

Confused, or what!

Dave

 

[Desperado]

I had a bit of time at the end of a meeting to research the type of disk drives in the 8296 and came across this interesting text at https://www.oldcomputr.com/commodore-8296-d-1984/:

>>> the drives in the 8296-D use the uncommon quad-density disks, like the 8250 and 1001. I have used double density disks for some tests and they worked fine.

Another website at http://www.computinghistory.org.uk/det/31789/Commodore-Pet-8296-D/ refers to:

>>> ... were sold as 8296 or, with a built-in 8250 dual disk drive, as 8296-D.
>>> The top of the line Commodore Pet 8296D computer with integrated 8250 high density drives.

You 'may' be OK with DS/DD disks - but (if they are old) you may not be lucky.

You may need to look around for some QD or HD disks - or keep trying DS/DD disks until you find one that works...

We really need to know what physical disk drives are fitted.

Dave

Good Evening Dave, this 3M Floppy disk are old but new....in 8050 drive works correctly...
Ok i try to look what drives are fitted

 

[daver2]

>>> 3M Floppy disk are old but new

How old? Do they actually rotate? I had some "old but new" disks - but they didn't all rotate when I tried to use them!

You can tell from the ROMS at UL1, UH1 and UK3 of the disk controller board possibly what disk drives are fitted.

The drives should then match the service manual. Of course, Commodore could have changed the drives later than the service manual I have identified for the 8050/8250.

Dave

 

[Desperado]

I just disassembled the drives, I will take the opportunity to clean them!

 

[daver2]

Might be worth reading this website: https://dfarq.homeip.net/commodore-sfd-1001/.

>>> Sounds a little like the 1.2 megabyte high density drives in the IBM PC/AT, doesn’t it?

>>> It’s a similar drive capacity-wise. But it uses a different type of disk. The SFD-1001 won’t work with PC high density disks. Quad density disks are hard to find, and they were even hard to find in the 80s. It turned out that you could format regular double density disks (the same disks used in the 1541) as quad density disks and they usually worked. No disk manufacturer would guarantee them if you did that, of course. But with no other options, people did it. Of course, it’s better to locate and use actual quad-density disks in the SFD.

>>> Quad density disks and drives are unusual, and not a lot of computer makers used them. Leave it to Commodore to find an oddball format and use it.

The mentioned unit appears to use the same physical floppy drive that you have.

Incidentally, I also found a German website stating that these disk drives suffer from electrolytic capacitor problems. Whether this is true or not of course I can't say.

Dave

 

[Desperado]

great explanation, thank you very much!

Now I have cleaned the lenses and lubricated the guides ... later I try to see if there are improvements ... otherwise what do you recommend? You say to change the capacitors?