Early IBM 5150 Floppy Disk Adapter

[DumpDumpDUmp]

I have an IBM 5150 with an early version of the 5.25" Diskette Adapter.

When attempting to read from the drive, it spins up but I get a "not ready" error.

I have tested the drive itself with another control card and it is confirmed working. I don't have another cable to test, but I've done a continuity test on this cable and it seems to be good. So my assumption is that the control card is bad.

I'd love to keep this machine as original as possible so I'm hoping to repair the card and would love any guidance anyone could offer.

Thanks!

 

[modem7]

Welcome to these forums.

Some basics:
- Do a thorough visual inspection. (Example failure.)
- Do a decent clean of the fingers on the card's ISA edge connector.
- Try the card in a different slot.

 

[modem7]

I have an IBM 5150 ...

No 131 error, the absence informing us that minus 5V is reaching the 5150 motherboard.

 

[DumpDumpDUmp]

Welcome to these forums.

Some basics:
- Do a thorough visual inspection. (Example failure.)
- Do a decent clean of the fingers on the card's ISA edge connector.
- Try the card in a different slot.

Thanks for the reply and thanks for the webpage-- its been a great reference to have for sure.

Visually, everything on the card looks great. I've cleaned the edge connector and tried multiple slots.

No 131 error and I've verified that the card is getting -5V (checked pin B5 with a multimeter). The -5V rail is a little low (4.8V) but I can't imagine that would be a problem.

 

[modem7]

No 131 error and I've verified that the card is getting -5V (checked pin B5 with a multimeter). The -5V rail is a little low (4.8V) but I can't imagine that would be a problem.

According to the 'Hardware Maintenance and Service' manual, the -5V can be as low as -4.5V (although, I would be concerned if it got that low).

What test equipment do you have? A logic probe? An oscilloscope?

 

[DumpDumpDUmp]

According to the 'Hardware Maintenance and Service' manual, the -5V can be as low as -4.5V (although, I would be concerned if it got that low).

What test equipment do you have? A logic probe? An oscilloscope?

Only a multimeter, unfortunately.

 

[modem7]

Only a multimeter, unfortunately.

You can't really do much with that alone.

Unfortunately, I don't think you are going to hear something like "On those cards, over 80% of faults are due to chip XYZ." from anybody.

If the power-on self test (POST) displays a 601 error, I'm sure you would have informed us of that.

You have the early version of the card. Confirm for us that there is no jumper on P3.

The cable is the one shown at [here] ?

Do you see and hear the A: drive being accessed by the POST ?

When attempting to read from the drive, it spins up but I get a "not ready" error.

What are you booting from? A hard drive?

Is that DOS displaying "not ready", or some program that you are using?

 

[DumpDumpDUmp]

No 601 error (or any other errors).

No jumper on P3.

My cable is as shown, with the "twist." The drive is connected to the end of the cable, after the twist.

I am booting from an MFM hard drive and it is DOS displaying the "not ready" error.

The drive is accessed during POST. It spins up and the activity light comes on.

 

[ldkraemer]

Does the Floppy Drive at the end of the cable have the Terminator resistor installed?
It should be, if it is not.

Is the drive at the end of the cable strapped for DS1 in a DS{0..3} configuration OR
DS2 in a DS{1..4} configuration (as er what is printed on the Floppy's PCB?

Larry

 

[DumpDumpDUmp]

Does the Floppy Drive at the end of the cable have the Terminator resistor installed?
It should be, if it is not.

Is the drive at the end of the cable strapped for DS1 in a DS{0..3} configuration OR
DS2 in a DS{1..4} configuration (as er what is printed on the Floppy's PCB?

Larry

Terminator is installed.

I'm pretty sure its strapped for DS1/DS2. There's nothing printed on the PCB but it should be 3-14 closed either way, correct?

(As shown on page 26 here: https://retrocmp.de/fdd/tandon/TM100-1_TM100-2_48TPI_Operating_and_Service_Manual_1983_OCR.pdf)

 

[modem7]

I'm pretty sure its strapped for DS1/DS2. There's nothing printed on the PCB but it should be 3-14 closed either way, correct?
(As shown on page 26 here: https://retrocmp.de/fdd/tandon/TM100-1_TM100-2_48TPI_Operating_and_Service_Manual_1983_OCR.pdf)

Yes, per the bottom-right of the diagram at [here].

 

[modem7]

There is some stuff you could try at [here], but from from what you have described so far, I expect that those will work.

If so, some other possible problem causes are:
- Index pulses from (good) drive are not reaching the floppy controller chip (uPD765).
- Index pulses from (good) drive are reaching the controller chip, but the controller chip is faulty in a way that affects the processing of index pulses.
- A problem somewhere in the circuitry that processes the data from the (good) drive.

When attempting to read from the drive, it spins up but I get a "not ready" error.

... and it is DOS displaying the "not ready" error.

I had a think about DOS reporting 'not ready'. A question is, "What is it that is not ready?" The best that I could come up with is the RDY pin on the floppy controller chip (uPD765), but the circuit diagram shows that the pin is unused.
Maybe our 'resident' expert, Chuck(G), knows.