CBM 8050 DUAL DRIVE NOT WORKING

[Desperado]

Hi guys, can someone help me to repair this dual drive?
When i turn on, can i see only blinking leds....i just tryied change RRiot ic with a replacemente board but i have also same defect
This is video:

 

[VERAULT]

Hmm, Seems stuck in a loop. Its supposed to blink a couple times then turn solid.
Is this a new find or did it used to work for you?

 

[Desperado]

Hi Verault,
i bought this floppy used with a 8032 cbm pet

 

[VERAULT]

Ah so its never worked for you.. Ok

Have you done the preliminary re-moving and resocketing of chips to see if it makes a difference. As well as voltage checks? Could just be some bad logic. Thats usually the culprit on these commodore drives.

Here is all the info you should need for the 8050 http://www.zimmers.net/anonftp/pub/cbm/schematics/drives/old/8050/index.html
You can use it to do voltage checks first just to make sure everything is working power-wise.

Any particular reason you thought it was the rriot chip?

 

[daver2]

>>> Any particular reason you thought it was the rriot chip?

The maintenance manual for the 8050 and the blink code.

Dave

 

[VERAULT]

5 blinks says it could be the 6502 as well.

 

[Desperado]

I changed also CPU 6502 but i have always same problem....

 

[VERAULT]

Well code 5 and 1 are both zero page. 4116 RAM might be a good place to start. Do you have any spares or a machine you can check them in?

 

[Desperado]

Yes i have some 4116 ic ram and i have ram tester also!

 

[Nivag Swerdna]

5 blinks says it could be the 6502 as well.

Indeed, From my memory of the last time I looked at my Fred the Floppy, five blinks means that the primary/IEEE-488 6502 (UN1) queued a request to the disc controller 6502 (UH3) but never got a response. Obviously quite a lot can go wrong during that handshake but much has gone right to get to that point... e.g. Zero Page RAM, Shared RAM and ROM check (for Primary) will have completed. Swap the two 6502s and see what happens?

 

[Desperado]

Indeed, From my memory of the last time I looked at my Fred the Floppy, five blinks means that the primary/IEEE-488 6502 (UN1) queued a request to the disc controller 6502 (UH3) but never got a response. Obviously quite a lot can go wrong during that handshake but much has gone right to get to that point... e.g. Zero Page RAM, Shared RAM and ROM check (for Primary) will have completed.

Thanks! So where i can start??

 

[Nivag Swerdna]

Thanks! So where i can start??

Swap the two 6502s and see what happens?

 

[Desperado]

Swap the two 6502s and see what happens?

Ok this evening i'll try this, thanks

 

[Desperado]

Hi, i swapped the two 6502 mos but nothing happens
I am desperate

Yes i have some 4116 ic ram and i have ram tester also!

This dual drive has 2114 rams

 

[Nivag Swerdna]

>>> I am desperate
Not sure what you expect... this might require some proper board level repair skills.

>>>Hi, i swapped the two 6502 mos but nothing happen
Do you mean it does what it did before or it no longer flashes? If it has stopped flashing then you have a dead 6502?

 

[Desperado]

Hi Nivag, it does what it did before!
I can repair board....i have desolder gun...solder...scope and logic probe...but i need your great help please

 

[Nivag Swerdna]

I see you have already tried the 6530-038 RRIOT which would be the obvious next suspect...

Maybe probe the address lines of UH3 and see if this is busy...

... then look at the outputs of UC3, UD3, UE3, UF3 and look for stuck bits... ?

 

[VERAULT]

Hi, i swapped the two 6502 mos but nothing happens
I am desperate


This dual drive has 2114 rams

Sorry I was just glancing at page 17 on the service docs! My fault.

 

[Desperado]

is it normal that the closing flaps are like this? I tried to move it up and down but I don't understand if it should open or not ...

 

[VERAULT]

I couldnt say, my 8050 has the same style floppy drives as the IBM 5150 and Apple II disk II drives.