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Thread: Hoping to repair my 8250

  1. #11

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    I have built a 2364 adapter for my eprom programmer as per this webpage... I have been able to read 2364 masked ROMs using the 2764 device configuration.

    http://mess.redump.net/dumping/2364_mask_roms

    I haven’t built it to invert the CS line mind you though the guy does indicate how this can be done by wiring in a 74ls04 hex inverter ..... hope this will direct you to successfully constructing an adapter
    Last edited by AndyG; May 3rd, 2020 at 03:21 AM.

  2. #12

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    I think you are safe reading the 2316 eprom using the 2716 configuration on your programmer.

  3. #13

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    Quote Originally Posted by AndyG View Post
    I have built a 2364 adapter for my eprom programmer as per this webpage... I have been able to read 2364 masked ROMs using the 2764 device configuration.

    http://mess.redump.net/dumping/2364_mask_roms

    I haven’t built it to invert the CS line mind you though the guy does indicate how this can be done by wiring in a 74ls04 hex inverter ..... hope this will direct you to successfully constructing an adapter
    Actually was able for read Consistently the 2364 ROMs from a 8050 by connecting CS to VCC on the 2364 (had a switched 24 adapter so tried it) and leaving pin 20 CE on the 2764 part of the adapter disconnected (ie not connected to the 2364). Rom dumps where identical to that found on Zimmers.net so we’re good reads.
    Last edited by AndyG; May 3rd, 2020 at 07:43 AM.

  4. #14

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    Thanks very much for the link and information on reading the ROMS.

    Some Success!!!

    I had a revelation late last night when I was looking for the ROMs for the 8250 to download to my PC. On a site, the description of the GCR ROM file said that it was an SFD-1001 file. I quickly opened up my SFD, and discovered that not only is the GCR rom (901467-01) identical to the one in the 8250, but so are the two DOS roms (901887-01, 901888-01). Given that I have a working SFD, I figured, this would be my chance to rule out these roms.

    http://www.zimmers.net/anonftp/pub/c...001/index.html

    The plan was to try the 8250 ROMS in my SFD, and see if any of them caused the SFD to fail. I first tried the GCR rom, and no difference, SFD was fine. So, the GCR rom is good. Then I tried the 901887-01 and the same result, SFD was good. BUT... the 901888-01 rom was an entirely different story. When I put that in my SFD, the error light started flashing and the drive light stayed on, exactly like the 8250.

    So, I put all of the original 8250 ROMS back into the machine except the 901888-01. In that position, I put the known good one from the SFD. And the error went away! The joy was short lived unfortunately, but this is what I see now when doing a ? DS$ after powering it up.

    sm_IMG_2218.jpgsm_IMG_2219.jpg

    Was thrilled to get to this point. So, what I did next was take a couple of SFD formatted diskettes, and tried to catalog them in the 8250. What I quickly discovered was, when I did a catalog, the drive lights did not come on when it was trying to read each disk, and each drive reports an error. I did a video so you can see the behavior now.



    Please excuse the dirt in the drives, I have not yet gotten to cleaning it as up to this point I couldn't even get the drive to boot up. Now that the digital board is booting as you can see, another problem has reared it's head.

    My next step is going to be to clean the drives, so I'll take them out and clean all the dirt off them, lube up the points that look like they could use a little work, then re-assemble. I suspect however that this isn't going to fix the problem. I believe that when accessing the drives, the drive light should come on, on each respective drive.... so I think there is still a problem.

    Have any of you ever encountered this new problem? Where, when you try to access the drive, that the drive light doesn't come on? I'm suspecting that that's part of the problem that the drive isn't reading disks...

    So to recap, so far I've found the following chips to have been bad in the drive.

    UH3 -6502 - BAD/replaced
    901888-01 - Disk Operating System (DOS) ROM high. - BAD/replaced

    While I was testing, I also tested to see if my RRIOT replacement had actually worked, and I'm happy to say that that works as well, even though the factory RRIOT chip is good, it was fun to confirm that I did that right.

    I will still need to make a new rom for this drive, so I can put my SFD-1001 back into service, so that's something I still will need to address.

    Has anyone encountered this new problem I'm seeing before in their travels?

    Thomas

  5. #15
    Join Date
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    Quote Originally Posted by AndyG View Post
    I think you are safe reading the 2316 eprom using the 2716 configuration on your programmer.
    Yeah, sorry for the ambiguity; I meant you'd either be able to read it or not depending on how chip select was programmed but AFAIK the 2K chips like the 2316/6316 all used 'normal' low-going CS so you should be fine.

    Interesting that tying CE to Vcc works; I always thought it might but never tried it.

    Here's a good selection of ROM adapters, including one that handles high CEs:

    http://store.go4retro.com/adapters-1/

  6. #16

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    Thanks for the link to the adapters and eprom information thus far. I've been to his site a number of times, but never noticed all the adapters he sells. I will for sure check them out.

    It was mentioned to me that perhaps the LEDs were not connected to their correct respective drives. I don't think the LED's are connected incorrectly to the drives, and the reason I say this is this...

    In my previous post, I state that the drive LED's don't come on when I do a CATALOG of either drive... However, having played around with the machine a bit more today, I noticed that if I do a COLLECT D0 the drive light comes on, on Drive 0. If I do a COLLECT D1, then the Drive 1 LED comes on. Again, I get an error when I try to do this.

    If I try to do a LOAD"0:*",8 however, the drive LED does not come on. Neither does it come on when I do a LOAD"1:*",8

    I had not tested the COLLECT command before, and was surprised to see the drive LEDs come on for that one. It's really got me scratching my head.

    So, if feels like there is something fishy going on with this machine. I would think that any time I access a specific drive D0 or D1, it's respective drive activity LED should illuminate. Not just when I'm issuing the COLLECT command... And I'm thinking that the fact that it's not reading tested disks might have something to do with it.

    Anyways, if any of you folks have come across this new issue before, or you have some thoughts on the matter, I'd love to hear it.

    Thanks,
    Thomas

  7. #17

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    Well, I spent a couple hours cleaning the drives, and really there was very little dirt on the heads. Everything is clean and lubed up that should be. It behaves exactly the same. I even tried brand new quad density disks in there, just in case it was finicky and wanted the quad density media, still, the same thing.

    I checked the GCR rom and every other IC in a socket to ensure they were properly installed, and they are.

    I even measured the resistances of the read/write/erase heads, and although I wasn't able to 100 percent for sure confirm I was checking between the correct points, I got very close to the readings shown in the 8250 service manual, on all four heads of the drives.

    So, I'm (yet again) at a loss. I was so hoping that cleaning up the drives would resolve the problem. The drives run nice and quiet now. The belts on the drives look to be in really good shape as well. Nothing looked bad on the drives. They were just a bit dirty, but that I cleaned off. Cleaned the drive screws till there was nothing left on it, then put a little bit of white lithium grease on them. Super smooth now.

    I bought another partially working 8250 that's currently enroute to me. The drive I bought has a drive 0 that can read disks and a drive 1 that will not. So, that's at least closer to working than mine is. Figured I could perhaps try swapping out boards and drives to see if I can isolate which major component is having troubles. Short of doing that, I seriously have no clue as to where to go next.

    The drive now boots up perfectly, with no errors. It accesses both drives. Just won't read or write (which kind of defeats the purpose) Heh.

    Also finding that the COLLECT, HEADER and LOAD commands will activate their respective drive LEDs when accessing them. The only command that will not activate the drive LEDs is the CATALOG command. When I issue that, each respective drive tries to get a directory, but fails on a drive not ready error. The COLLECT command fails on a read error 21 on track 39 (think that's what it's telling me). And trying to load the first thing off the disk gives me a file not found.

    Still, I'm wondering if the analog board has a problem. Given that this machine had two dead chips in it (one 6502 UH3) and the 901888-01 DOS Rom, I'm wondering if something else happened to another chip maybe on the analog board, or even on the digital board. But I don't know how to figure that out.

    Anything to suggest anyone? Anything is appreciated. I feel like I've come such a long way, would be a shame to have to walk away from the drive at this point.... In the end, maybe I can advance a bit further with the drive that's coming in the mail.

    Thomas

  8. #18

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    Quote Originally Posted by COREi64 View Post
    Thanks for the link to the adapters and eprom information thus far. I've been to his site a number of times, but never noticed all the adapters he sells. I will for sure check them out.

    It was mentioned to me that perhaps the LEDs were not connected to their correct respective drives. I don't think the LED's are connected incorrectly to the drives, and the reason I say this is this...

    In my previous post, I state that the drive LED's don't come on when I do a CATALOG of either drive... However, having played around with the machine a bit more today, I noticed that if I do a COLLECT D0 the drive light comes on, on Drive 0. If I do a COLLECT D1, then the Drive 1 LED comes on. Again, I get an error when I try to do this.

    If I try to do a LOAD"0:*",8 however, the drive LED does not come on. Neither does it come on when I do a LOAD"1:*",8

    I had not tested the COLLECT command before, and was surprised to see the drive LEDs come on for that one. It's really got me scratching my head.

    So, if feels like there is something fishy going on with this machine. I would think that any time I access a specific drive D0 or D1, it's respective drive activity LED should illuminate. Not just when I'm issuing the COLLECT command... And I'm thinking that the fact that it's not reading tested disks might have something to do with it.

    Anyways, if any of you folks have come across this new issue before, or you have some thoughts on the matter, I'd love to hear it.

    Thanks,
    Thomas
    Well, I don't have a 8250 (you're lucky) but I have two 8050.. both not working at the moment (maybe I should do something about that..).

    In the 8050/8250 service manual it states that you should check the 12V supply line and UM3 (6522) and UJ2(74LS00) if the motor doesn't run. Will it run or is it completely silent?

  9. #19

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    Everything about this drive appears to be working, except for the fact that it won't read or write to disks.

    The drive boots up fine, no error codes.
    Drive lights work
    Heads on both drives move when trying to format, collect, load, initialize...
    Motor spins the disks just fine.
    Drives are clean, heads are clean
    Testing with DS/DD as well as Quad density disks. Old ones AND brand new ones.

    Resistances for all four heads appear to be in the realm of normal.

    So, where to go from here is really the big question. I watched a video last night, where a guy that was restoring an 8050 had the exact same problem as me, and it turned out (for him) that it was one of the 6532 RIOT's that had a stuck bit. He replace it and his drive started working. So, I tried the two 6532 RIOT's out of my working SFD in my 8250, and there was no change in performance.

    One thing that I did note however which is kind of inconsistant in my testing.

    On three occasions, when I was doing a header on D1, it came back to me with "bad disk". I've tried header'ing disks many times, but that's only happened three times.

    When I do an initialize, like this, it returns to me successfully and the ?DS$ reports all zeros, and ok.

    OPEN 15,8,15,"I0:":CLOSE15

    Last night, when I was trying the COLLECT command, on a couple occasions, I was getting a write protect error, even though the disk in the drive wasn't write protected. I did the initialize command and that never came back.

    So, I am seeing some minor inconsistant performance, but never able to read known good disks, or get any of the commands to actually do what they're supposed to (other than spin up the drives and move the heads).

    Thomas

    Quote Originally Posted by Kakemoms View Post
    Well, I don't have a 8250 (you're lucky) but I have two 8050.. both not working at the moment (maybe I should do something about that..).

    In the 8050/8250 service manual it states that you should check the 12V supply line and UM3 (6522) and UJ2(74LS00) if the motor doesn't run. Will it run or is it completely silent?

  10. #20

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    Oh, really. That sounds more like some problems with the analog drive card. Do you have the right ROMs for the drive you are using? See page 2 in the service manual.

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