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Need help with a finicky Qumetrak 142 floppy drive (PCjr)

djfitzgerald

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I started work on a PCjr at the March VCF East repair workshop, and have been running into some issues with the floppy drive. I have been having intermittent problems with it playing a game, and suspect a possible drive issue. I'll presently describe what I did and what I observed, and would be interested in hearing anybody's thoughts on what could be the root cause of this problem.

At the workshop, the floppy drive had been all bound up and Sark (who was working on two other bound PCjr Qumetrak 142 drives for the VCFED) worked on lubricating it until it could read again. When I got home, I started playing with the drive myself. I made a King's Quest I floppy from an image on Archive.org, and tried to load it in the drive. It would work only intermittently. I tried making the disk image with three different floppies and got the following results:
  1. Floppy One - This was a non-name floppy that may have originally come from boxed software. On the second or so time I tried booting it, I was able to get to the actual game. However, subsequent tests would only get as far as the program splash screen before stopping. The text input prompt (below the splash screen) would show a '±' character in blue after the white prompt '>', and if I hit the ENTER key, the disk drive would read but that prompt and symbol would come back and I couldn't make any more progress. When I finally gave up and reformatted the disk on a Windows 95 machine, it reported a number of bad sectors, which was probably the cause.
  2. Floppy Two - This was an older IBM-branded DD floppy (blue label with white text). I could not get the PCjr to recognize it as a bootable disk. One time after starting with Floppy One and getting stuck at the prompt, I swapped it for Floppy Two and upon hitting ENTER the game would load. When I took the disk drive out of the PCjr, I saw that the hub would get stuck with this particular floppy in the drive: it would start spinning, but then get physically stuck a bunch. I tried to disassemble the drive and remove the hub so that I could lubricate its' shaft, but I couldn't get the hub off the shaft. Instead, I sprayed WD-40 silicon lubricant underneath the spindle pully (the part attached to the bottom of the hub and its' shaft) in the direction of the hub's shaft. This seemed to fix the intermittent sticking problems, but the PCjr still couldn't read the floppy as bootable. When I reformatted the disk on my Windows 95 machine, it reported no bad sectors.
  3. Floppy Three - This was a newer IBM-branded DD floppy (yellow label with black text). The PCjr recognized the floppy as bootable and went into the game. The first time I played with it, I got past the splash screen, and to the first game screen. I walked over the bridge to the second game screen, opened the door, went down the hallway (third game screen), made a left turn (fourth game screen), and entered the throne room (fifth game screen). I talked to the king and got his monologue. Thinking that everything was fixed, I put the PCjr back together and invited my roomate down to play the game. She got as far as the third game screen, but when she left the screen to make the left turn, the computer started to read the disk and the fourth game screen would never load. We tried this after a number of restarts and got the same result each time. When I reformatted the disk on my Windows 95 machine, it reported no bad sectors.
 

ibmapc

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Of coarse I can't be sure, because I wasn't there when the drive was lubed, but it sounds like you might need to be a little more thorough with the cleaning and lubing of the carriage rails. I once pulled a drive from a PCjr that must have been in a smokers house. The rails were very sticky and required multiple cleanings with alcohol to get it working reliably. I believe the only way to get adequate access is to remove the pc board from the drive and repeatedly apply alcohol and wipe, moving the carriage back and forth until it moves without sticking anywhere in its travel. Then, apply a small amount of silicone lube and move it back and forth again. Of coarse, don't force anything. You don't want to change the alignment or damage the heads.
 
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jafir

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Can you run IMD and check the RPM and alignment? I had a full height MPI drive in a 5150 that did a pretty good job of reading the first few tracks be when you’d step too far forward it wouldn’t always make it where it was supposed to go. I think thorough cleaning, lube, and some exercising got that one working a little bit better. I think some of those drives get sticky spots on the bearings in the motor. I’m not sure if the PCjr drives are similar.
 

Chuck(G)

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I grabbed a 142 off the shelf and had a look. Do check the drive RPM, as this is a brushed-motor belt-driven drive. The belt could be slipping or the motor speed have drifted (there's a blue trimmer pot on the back edge of the PCB to adjust speed). If you have to clean the rails, you'll have to remove the PCB to get at one of them. It's not a hard job, but pay attention to the nylon bolt holding the TO-220 transistor near the rear of the PCB. Do not remove the bolt; rather unscrew the bracket from the bottom of the drive. Do not lubricate the rails after cleaning. If they really need some lubrication, I suppose a light coating with the pure silicone spray wouldn't hurt. Grease, oil, etc. will only attract and pick up dirt which will migrate into the sliding surfaces.

The 142 isn't a bad drive, just not my favorite when compared to, say, the direct-drive Teac FD55 drives.
 

SomeGuy

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"reformatted the disk on my Windows 95 machine" keep in mind that disks formatted using a 1.2mb drive are NOT reliably readable in a 360k floppy drive. One has to use either a genuine 360k drive or first degauss the disk.

I obtained a couple of Qumetraks like that and they did not want to behave reliably until I exercised them a lot.

Don't try to test problems like this with random games or applications - just too roundabout and they won't tell you what is going on. That also won't usually step the head over all possible tracks.

What I would do is make a boot disk with Norton Utilities 4.5 Disk Test (DT.EXE) and put that in a batch file to repeatedly loop testing the disk surface over and over. Let it run for a couple of hours. Of course, if it stops with read errors, then there is some problem that needs to be addressed.

The belts do slip easily. Any disk that may take more force to spin - such as cleaning disks or disks that are warped - may not want to spin properly. As suggested, gently clean the belts.
 

djfitzgerald

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Thanks for all the help, folks! I have still been having intermittent problems reading disks. For example, sometimes the DOS 2.1 boot disk I made was giving me "bad config.sys" errors, and sometimes not. I put DI on that disk and made a batch file that ran DI A: \N \B in an infinite loop. I ran it for about three hours last night, it reporting no errors. I'm running it again now. I had previously lubricated the rails with WD-40 silicone spray and am hoping that exercising the drive like this for some time will just "make the problems go away" (I can always dream, can't I?). If this doesn't do it, I'll go back and check the RPM and the belt.
 

DDS

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"I had previously lubricated the rails with WD-40 silicone spray..."

Be careful with silicone spray. It tends to migrate to places you don't want it to be. For things like drive rails etc a thin coat of a silicone grease would be better.
 

Chuck(G)

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The problem is that "silicone lubricant" often has oil in it as well as the silicone, so read the contents on that can carefully. And use pure silicone sparingly--you don't need much.
 

ibmapc

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Do check the RPM as mentioned previously. I recall the drive that I worked on that was all gummed up had trouble maintainig the correct RPM. I tried to adjust with the POT on the pcb but it would not spin at a consitant speed until I managed to lube the spindle motor and spindle bearing. I can't recall the method used to lube it. Maybe someone here can offer advice as needed. As mentioned before, you don't want excessive lube going places it doesn't belong.
 

djfitzgerald

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Do check the RPM as mentioned previously. I recall the drive that I worked on that was all gummed up had trouble maintainig the correct RPM. I tried to adjust with the POT on the pcb but it would not spin at a consitant speed until I managed to lube the spindle motor and spindle bearing. I can't recall the method used to lube it. Maybe someone here can offer advice as needed. As mentioned before, you don't want excessive lube going places it doesn't belong.
How were you able to lube the spindle bearing? I couldn't figure out how to disassemble it, or if doing so was even possible.
 

djfitzgerald

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The problem is that "silicone lubricant" often has oil in it as well as the silicone, so read the contents on that can carefully. And use pure silicone sparingly--you don't need much.
Well crap. What would you recommend using to clean it off the rails so that I can relube it with the proper stuff?
 

ibmapc

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Well crap. What would you recommend using to clean it off the rails so that I can relube it with the proper stuff?
I would not worry to much about the lube you now have on the rails. Just check it once in a while to see if the carriage is moving freely by hand. If it gets sticky, use some Isopropyl Alcohol to clean them. I don't remember how or even if I succesfully lubed the spindle on mine. It could be that after enough exercising, it freed up some. Others here might have an Idea, but all I can say is that if the spindle and spindle motor don't turn freely, it won't maintain proper RPM.
 
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