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Commodore 8050 disk drive

Max1227

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Hi all,

A while back I posted on this forum about the commodore 8050 disk drive that I purchased. I later sent the board off to someone who knows exactly how to repair PET's and their accessories, however he to is unable to diagnose the fault with the disk drive.

All the socketed chips on the board are working perfectly and the PET does recognise the disk drive when plugged in. The drive also responds to commands made by the PET however it cannot read/write or format a diskette. I was wondering if any one else has encountered this problem and can help me try to work out what is wrong with the drive.

Any help/suggestions would be much appreciated.

Thank you,
 

billdeg

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Both drives same symptoms exactly? What are the rpm's of the drives? Condition of caps?

What does computer return when you enter this command:
?ds $

What comand are you using to list directory / format disk?

I assume there is no blink code, just green/red/green when powered on.

Note: each time you test something and it fails, power cycle the drive. It helps.

B
 

KC9UDX

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Billdeg nailed it, we're going to need a ton of information to help. If an expert can't fix it on his bench, we're going to have a heck of a time.

Have you cleaned both disk heads?

Is there any mechanical activity on read/write commands?

Have you tried formatting diskettes?

Have you tested or replaced the RAM?
 

Max1227

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In response to Billdeg's message:

1) No, this is the same drive as the one I posted about a while back (I've spent a lot of time trying to fix this and getting nowhere)

2) condition of caps are good and all the dodgy looking ones have been replaced. I don't know the rpm of the drives but all I know is that I tested the speed of them with a strobe light and they are fine.

3) I remember using this command but with 'print'? It returns what you would except (can't remember), it was something like 75 commdodore DOS....

4) Command to format disk was 'header' (I think) and the directory is 'catalog'.

5) At first the drive did give no error code. But now he tells me that it blinks 4 or 5 times which are unused error codes??

In response to KC9UDX:

1) I did clean both heads, it made no change.

2) When you ask the machine for a 'catalog' the heads move across the area where the directory is but it returns and error code on the PET. I think it was error 21. When I format the disk the drive also responds and makes the correct noises but the heads don't move.

3) RAM hasn't been tested, but is presumed fine as it doesn't give any RAM error codes/blinks.

I have put a copy of his email in the post so that you can see what he thinks the problem is.

Yes, with a working 6522 it is showing either 4 or 5 flashes, so the 6522 you have probably works (or at least works better than the one that was fitted). I have verified that all of the chips not soldered down work fine on another 8050 board.

So it looks like there is a problem with some of the other circuitry. Probably not the RAM as it should test that and report a different error. So it's somewhere in the glue logic, address decoding or buffering.

It's going to take a while longer I'm afraid.

Thanks,
Max
 

KC9UDX

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Does the RAM get tested?

I had bad RAM in my D9060 and the only symptom was dodgy communication between the two 6502s.
 

billdeg

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You're going to need to be more precise. I don't know who is fixing your drive but they need to be more accurate in what he/she reports to you so you can be more accurate in what you report here.

In response to Billdeg's message:

1) No, this is the same drive as the one I posted about a while back (I've spent a lot of time trying to fix this and getting nowhere)

I meant, drive 0 and drive 1 of the same 8050. Sometimes one drive will work fine and the other will not.

2) condition of caps are good and all the dodgy looking ones have been replaced. I don't know the rpm of the drives but all I know is that I tested the speed of them with a strobe light and they are fine.

Looks means nothing, you have to measure the caps ESR, but for now let's say we really don't know for sure if you have no actual measurements.

3) I remember using this command but with 'print'? It returns what you would except (can't remember), it was something like 75 commdodore DOS....

Gotta do this *exactly* after a fresh power-on cycle:

?ds$ [return]

The command: ?ds$ will tell you if the processor board of the disk drive is OK or not. The response you want will be something like: "73, cbm dos v. 2.x"

4) Command to format disk was 'header' (I think) and the directory is 'catalog'.

Before you use a disk you must format it. The command is:
header "disknamehere", d0, i01
(assuming you have a disk in drive 0 of an 8050 drive). NOTE: i01 assigns the identification name/number; 01” can be substituted for any two alpha characters. The system will respond "Are you sure? Y/N" or something like that before the format commences.

if you want to format a disk in drive 1 the command is
header "disknamehere", d1, i01

(if you re-format a disk, best to use a new value for i each time - i01, i02, i03, etc.)

"catalog" is not a CBM command. Just use the same two step commands you'd use for a c64 to run a directory:

load "$",8,0 (to see what's on the dist in drive 0, the right drive)
load "$",8,1 (to see what's on the dist in drive 1, the left drive)

follow the above command with LIST to see the directory.

Newer PETs have other directory commands (such as "DIRECTORY") available, but for sure you can use the above command on any PET except the oldest 2001's (with ROMS that pre-date the 2040 drive).

If the drive seems OK but will not locate (file not found) or run programs, try this:

open1,8,15,"I" (return)

...this command will help the drive head find its way back on track. That and cleaning the drive head itself with isopropyl alcohol is often the solution to a lazy drive.
5) At first the drive did give no error code. But now he tells me that it blinks 4 or 5 times which are unused error codes??

not good. You need to fix this first before you can do anything much.

4 flashes: there is no 8050 blink code of 4 flashes /unused
5 flashes: means that you have a controller ROM issue. See K3 and H3 on the 8050 board (check ROM/6530/6502)

If the drive light does not end in green you can't go much farther.
 
Last edited:

KC9UDX

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"catalog" is a valid "BASIC 4" command. It's the same function as "directory".

I use it exclusively as "cA".

"cAd0" gives the directory of drive 0, "cAd1" gives drive 1.

And not to pick nits but it is important to note the initialize command is
open1,8,15,"i" or oP1,8,15,"i"

With of course a close1 or clO1 down the line somewhere.

Else, very good points.

I would add that I think it's important to know for certain if it ever really does four flashes or not.
 

billdeg

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CATALOG is not a command in the drive ROMs in any manual I have for the 8050 or PET 8000 series at least. I was trying to avoid BASIC 4 but I should have been clearer as to my meaning why to avoid it. I don't know what kind of PET he's using. CATLOG would be translated into something an 8050 would understand, but from a support standpoint you're adding a new variable for no valued reason. I'd avoid using a command that is not read natively by the ROMs of the 8050 at this phase of testing.

Not trying to initialize, I meant to bump the heads. Try this for yourself:

open1,8,15,"I" (return)

It bumps the head straight. Just a trick I got from an old 1982 TECHTOPICS bulletin.
 

gsteemso

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Are you certain of that syntax to load the directories? As far as I know, it is LOAD"$0",8 / LOAD"$1",8 rather than putting the desired drive number in the secondary address. I can’t recall whether LOAD"$",8 without a drive number lists both directories mixed together or just the one most recently accessed.
 

Max1227

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1) Yes both drives respond in exactly the same way.

2) By replacing dodgy caps I meant he has tested them all and replaced the dodgy ones.

3) Yes I did this and it gave me the message you posted earlier. The '73 CBM DOS.....' after a 'catalog command or a 'Header' command this changes to '21.....', I cannot remember any of this since it has been with the specialist for nearly 1.5 months.

4) Yes I did remember what the command is. It doesn't work and the drive spins endlessly and the head does not move.

5) 'Catalog' is a valid CBM command, otherwise why does it work?? Also I think 'directory' is a valid command as well, as this works on my PET (4032), you can also shorten this to 'DI' then a graphics symbol which I cannot remember. Isn't 'DLOAD' another way of loading from the disk drive?

6) It used to show no error codes but I realised that the 6522 chips was faulty and replaced that, which then showed an error code of 10 blinks for me and 4 blinks for him.

Thanks,
 

billdeg

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OK.

CATALOG will work. Got it. Not important how you run a directory, especially when you have blink codes making it all moot anyway.

10 blinks = ROM
4 sometimes means 6502 (CBM hard drive), but I read 4 flashes is not used by the 8050 ROM.

I suggest you consult this collection of docs I put together URL below that will help you take things further.
http://vintagecomputer.net/commodore/IEEE_drives/CBM_IEEEDriveNotes.pdf
(ignore the B Series stuff and skip downto the 8050 diagnostics/tips)

should help

Bill
 

Max1227

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He tested all the socketed chips by other means e.g. putting one into an Atari 2600, so they all work.

Thanks for the PDF, Ill have a look through it and see if I find anything relevant.

If the 8050 doesn't test RAM on startup, although I though it did, then is it possible that this fault could be cause by a RAM module failing?

Im not sure how much more information I can give you since that is all both him and I really know.

Thanks,
Max
 

KC9UDX

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Yes. Or first, shotgun the SRAMs. I usually do that. I just don't trust old SRAMs.

Bill, thank you for the clarification on "l". I misread it here as "I" (capital I) and had completely forgotten about "l". That is very good to know!

Matt

P.S. DIRECTORY and CATALOG are both BASIC 4 functions, $ is the only way DOS will spit out a directory. I've always used CATALOG because I'm a stickler for typing Commodore BASIC as efficiently as possible. cA takes less typing than diR. Not that it matters in direct mode. DIRECTORY needs three letters of course because it conflicts with DIM.
 
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