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SFD-1001 not formatting

It's seems hard to get a stable reading on the connector. But if I'm careful using my photos on the left row, White and Green give me about 9.0-9.5. on the right row White and Green reads about 5.5
 
Digitalman said:
It's seems hard to get a stable reading on the connector. But if I'm careful using my photos on the left row, White and Green give me about 9.0-9.5. on the right row White and Green reads about 5.5
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Ok, next step is to unplug the heads connector and repeat the white to green resistance measurement on the unplugged connector. You can use small solid copper wires (or resistor leads for example) to plug into the right connector holes and touch the other end of the wire with the multimeter's probes.
Frank
 
Ok, so again, it seems difficult to get a consistent reading and I don't know why, numbers seem to jump all over the place. I tried a few ways to get these numbers, touching the top of the pins, touching on the clips on the side of the connector, and I didn't have any copper wire but I has some leads that I had cut from some recently installed capacitors and used them in the pin holes.

In any case, the numbers are ~12 on the left row and ~5 on the right. Testing White to Green.
 
Digitalman said:
Ok, so again, it seems difficult to get a consistent reading and I don't know why, numbers seem to jump all over the place. I tried a few ways to get these numbers, touching the top of the pins, touching on the clips on the side of the connector, and I didn't have any copper wire but I has some leads that I had cut from some recently installed capacitors and used them in the pin holes.

In any case, the numbers are ~12 on the left row and ~5 on the right. Testing White to Green.
Click to expand...

Ok, the unstable readings might be because the cable is intermittent, but it really depends how unstable, and it also depends on your multimeter.
Having said that, I'm afraid one head (the one with 5 ohms on the erase coil) has issues, that's why it can't format. I suggest you to try actually writing something on the top side on a formatted disk to see if it's indeed possible. One way would be filling one disk at least to more than half the block capacity, so we are sure it needs to write on the top side, then issue a V0 command that reads all the files, make sure you catch errors also, so don't close the command channel before V0 ends. Another way would be using a disk editor program and write sectors on tracks > 77, then reading back the same sector and verify there're no errors either when writing and when reading.
Frank
 
iz8dwf said:
Ok, the unstable readings might be because the cable is intermittent, but it really depends how unstable, and it also depends on your multimeter.
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Sometime readings were really high, 30s, 40s, 60s..etc.

iz8dwf said:
Having said that, I'm afraid one head (the one with 5 ohms on the erase coil) has issues, that's why it can't format.
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Is this repairable or is it just dead if that's the case? Is this a common failure?
 
Digitalman said:
Is this repairable or is it just dead if that's the case? Is this a common failure?
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If the erase coil is indeed failing short, there's no other option than replacing the head assembly.
I've found very few bad heads in my repair life, and this would be the first time I've seen a coil going on low resistance rather than open circuit. That's why I suggest you to try to write a formatted disk to at least half the blocks plus 1 or more, or try to write blocks in the top side tracks (> 77).
I would also think that the driver circuitry isn't happy to drive a load which is about half the expected one (doubling the required current). It might have already failed.
I think you don't have an oscilloscope handy, do you?

Frank
 
I made a quick video using Disk Doctor. As you can see I am unable to read any tracks from the top side of the disk. ☹️
 
billdeg said:
I would not expect disk doctor 64 work on an SFD-1001. Did you try loading https://www.vintagecomputer.net/commodore/SFD-1001/sfd-1001 test.PRG

I don't know if the program works on a C64 though, just realized that. It's for a PET or B series probably. I wonder if there is a C64-loadable version or diagnostic for a SFD-1001 or 8250 drive.
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Looks like that disk doctor recognizes the 1001 anyway. It's not giving an illegal T/S error, it's giving a 21 read error. What I find strange is that it doesn't even read the top tracks. I wonder if a failed driver is pushing current to the erase coil all the time. He would really need another DS/4D drive to confirm the disks are readable.
Well, if all else fail, it's still a SS/4D drive, provided he disconnects the top head.

Frank
 
billdeg said:
I would not expect disk doctor 64 work on an SFD-1001. Did you try loading https://www.vintagecomputer.net/commodore/SFD-1001/sfd-1001 test.PRG

I don't know if the program works on a C64 though, just realized that. It's for a PET or B series probably. I wonder if there is a C64-loadable version or diagnostic for a SFD-1001 or 8250 drive.
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Yes this is a version made for IEEE-488 drives. Got it from here. http://members.optusnet.com.au/spacetaxi64/MAIN/SFD1001.htm
I tried you program on an emulator but it just crashes or gives me an error. I assume it's not C64 compatible? Haven't tried on my real machine yet.

iz8dwf said:
.
Well, if all else fail, it's still a SS/4D drive, provided he disconnects the top head.

Frank
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On that note, is it possible to make it a single sided drive? Is there a DOS command or jumper I can set?
 
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Digitalman said:
On that note, is it possible to make it a single sided drive? Is there a DOS command or jumper I can set?
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Well you should surely disconnect the top head, since it might be trashing unintentionally the top side of the disk if a driver failed (I'd say it's likely). If you have formatted media that haven't never been in this drive, you could disconnect the green wire from the top head and try reading sectors on the top side, to confirm it's ok.
As for permanently tell the 1001 to only use SS format, I don't know, we need an expert :)
Frank
 
iz8dwf said:
Well you should surely disconnect the top head, since it might be trashing unintentionally the top side of the disk if a driver failed (I'd say it's likely). If you have formatted media that haven't never been in this drive, you could disconnect the green wire from the top head and try reading sectors on the top side, to confirm it's ok.
As for permanently tell the 1001 to only use SS format, I don't know, we need an expert :)
Frank
Click to expand...

What does it mean when you say "driver failed"?
 
The easiest way to do this is to use BASIC to make it think it's drive 0 of an 8050, which is single sided. I can't find it at the moment however...ug. maybe someone has this BASIC program and can post it for you
b
 
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Someone gave me this command for switching to single sided U0>M0 but I believe it is a PET command. I tried OPEN15,8,15,"U0>M0" in C64 BASIC but it doesn't do anything. Is there another way perhaps?

...after further investigation that does appear to be the command. It is the same one for 1571 drives but it doesn't seem to help me at all. I still get a READ ERROR at TRACK 78 when formatting. ....
 
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Digitalman said:
Yes...the start of the top side.
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Duh! Should have read more closely.

Never noticed before: are tracks numbered starting at one instead of zero (and sectors at zero instead of one) in the CBM world ?

Any idea what make/model the drive itself is?

Just catching up: you can read both sides and you can format/write side 0 but side 1 fails format with a read error?

Does it restore properly to track 1 after track 77?

m
 
Digitalman said:
Someone gave me this command for switching to single sided U0>M0 but I believe it is a PET command. I tried OPEN15,8,15,"U0>M0" in C64 BASIC but it doesn't do anything. Is there another way perhaps?

...after further investigation that does appear to be the command. It is the same one for 1571 drives but it doesn't seem to help me at all. I still get a READ ERROR at TRACK 78 when formatting. ....
Click to expand...

These commands don't run in the host computer, they run in the disk drive. You can issue these commands from a dumb terminal if you can figure out how to connect one to the drive. So any commands that are sent via a BASIC PRINT# or OPEN command will work the same on a given disk drive from any computer.

Can you swap heads and see if the problem moves to the other side of the disk?
 
KC9UDX said:
Can you swap heads and see if the problem moves to the other side of the disk?
Click to expand...
I assume I would do that by swapping the pins around on the connector?

I noticed in the schematics there is an S1 and S4 jumper that is associated with single side or double. If they are open they are single. But I'd have to cut the trace on the board to open it. Thoughts?
 
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