Issue with two different PCjrs - looking for troublesh help

[bloguidice]

Hi, all. I just recently tried to get back into the PCjr and acquired two different units. Both seem to exhibit similar problems, but I'm not really sure what the exact issues are.

On the 128K model with the parallel port sidecar (by the way, how do you remove a sidecar?), I get an error H with everything plugged in and I can't use the keyboard. If I remove the power to the disk drive from the power supply connection, the fan starts to whir again and I can use the keyboard. I can boot to cassette BASIC and cartridge BASIC.

On the 640K model with no sidecar, the drive light goes on after the bios memory test is done, but does not load a disk. I have no error message once it goes to cassette BASIC (just one beep), but I can't use the keyboard. With the disk drive power cable removed, I get Error H and can use the keyboard. I can also boot to cassette BASIC and cartridge BASIC.

I tried every combination of swapping parts and power supplies I could think of, as well as two different bootable disks. Is it likely that both systems have bad drives and/or disk controllers, or is it a power issue of some type I'd have to address with a power sidecar or something?

I posted two quick photos of the machines here: https://billloguidice.tumblr.com/post/6 ... 9109628928

Any help or suggestions is much appreciated. Thank you.

[Brutman]

Removing a side car: Sidecars are attached with four screws. You have to remove the plastic panel at the end of the machine to see the screws. The panel is held on by friction and the plastic is old so be gentle to ensure you don't break the standoffs that provide the friction.

Do you have a Guide to Operations manual? You really should have one.

Error H is a diskette controller or drive problem. Check to ensure the drive controller is secure in it's socket. Error H really should not affect keyboard operation so something else is going wrong - look for shorts caused by stray metal, swollen capacitors, etc.

On the 640K machine - are you testing with a known good diskette? If so, clean the drive heads and rails. If the machine fails to boot from a floppy it will go to BASIc, and that can be caused by read errors on the diskette.

[bloguidice]

Removing a side car: Sidecars are attached with four screws. You have to remove the plastic panel at the end of the machine to see the screws. The panel is held on by friction and the plastic is old so be gentle to ensure you don't break the standoffs that provide the friction.

Do you have a Guide to Operations manual? You really should have one.

Error H is a diskette controller or drive problem. Check to ensure the drive controller is secure in it's socket. Error H really should not affect keyboard operation so something else is going wrong - look for shorts caused by stray metal, swollen capacitors, etc.

On the 640K machine - are you testing with a known good diskette? If so, clean the drive heads and rails. If the machine fails to boot from a floppy it will go to BASIc, and that can be caused by read errors on the diskette.

Yes, I do have the Guide, but didn't note the removal of a sidecar. Thank you.

I'm assuming both machines have similar issues because I swapped disk controllers and disk drives between the two. I can only assume that both disk drives are bad and maybe one of the disk controllers.

What I find REALLY strange though is that when I connect power to the disk drive, the fan stops spinning. When I remove power to the disk drive but leave the fan power plugged in, the fan spins.

I assume my only course of action is to get a new disk drive and controller, as well as the sidecar power attachment. I'm not sure what else to troubleshoot at this point. Both machines seem to work fine otherwise.

On a side note if you don't mind, would you happen to know how the one PCjr has 640KB? I don't notice any extra modifications and assumed like with the 512K sidecar expansion (which I already have along with the necessary disk), it would need some type of driver to work.

[Brutman]

If you keep connecting a disk drive to the machine and the fan stops spinning, then put that disk drive aside - that sounds like a short somewhere, and who knows what kind of damage that will cause if it is left connected. Also, check the power cable - it should be keyed but I smoked a very nice hard drive years ago when I didn't realize the connectors were not keyed properly and things "just fit."

The controller is probably fine - those things are dumb as rocks. ;-0

If you have a machine that counts to 640KB and it has no sidecars, then look under the diskette drive tray. There is a probably a daughterboard under there that provides the extra memory. It will be connected through the CPU socket, interposing between the CPU and the motherboard. The BIOS will count the extra memory at boot time; you will need a device driver to get DOS to recognize the extra memory. (Check the main site .. all of this is documented.)

[bloguidice]

Thanks. It's just really strange that the same fan stops moving is exhibited when either drive is connected on either machine. It's two different disk drives and two different controller cards from two different computers.

Last question if you don't mind and then I'll stop bugging you. I recall when I had a PCjr in the past that I was able to connect it to my Commodore 1084S monitor and pretty much anything else via composite connection without issue. Now, when I try to use the composite out on either machine to the 1084S (including modern monitors and even things like the XRGB-mini and similar adapters), I get a badly distorted picture that's mostly black. When I use a PCjr to CGA adapter cable I get perfect output on my 1084S with both machines. Could that also point to some type of fault? Again, it's very odd that it's happening with two different machines from two different sellers.

[Brutman]

I'm not bugged at all. I'm supposed to be digging holes and building a retaining wall.

The composite output has always been rock solid for me and if your TTL output is working there is not a lot of extra circuitry to get to composite.

I hate to even bring this up, but you are plugging it into the 'V' port, right? There is another RCA jack connection on the machine for Audio over by the power switch and if you plugged in there you would have this problem.

[bloguidice]

I'm not bugged at all. I'm supposed to be digging holes and building a retaining wall.

The composite output has always been rock solid for me and if your TTL output is working there is not a lot of extra circuitry to get to composite.

I hate to even bring this up, but you are plugging it into the 'V' port, right? There is another RCA jack connection on the machine for Audio over by the power switch and if you plugged in there you would have this problem.

Definitely the V. I don't think I'd get a scrambled picture if I was using the wrong port. Thanks again.

[DoctorOctal]

It’s just really strange that the same fan stops moving is exhibited when either drive is connected on either machine. It’s two different disk drives and two different controller cards from two different computers.

If the (12V) fan goes off when you plug in a drive’s power cable, that’s a sure sign that the drive has a shorted 12V power rail—almost certainly by one or more of the tantalum capacitors sitting on that rail. It’s a frequent problem with these drives and is a straightforward fix if you’re comfortable with soldering.

Both of your drives are by Qume, and I’ve found that these often need mechanical help as well. The clean-the-heads-and-rails routine is the least of it. If you get a drive that isn’t already known to be in working condition, it may not be able to spin a disk at the right speed or at all. (To fix that you’d need to lube the collet bearings, maybe the drive motor shaft, and maybe the spindle. You might need to adjust the drive belt tension or replace the belt. Then you’d check and tweak the motor speed as needed.) In contrast, the much-less-common Alps drives usually work without a fuss.

As Mike said, the controllers are probably fine. They do have problems sometimes but are a lot less likely to fail than the drives.

Looking at the PCjr schematics, I see that a shorted 12V rail will shut down your keyboard cable, joysticks, and composite video because they’re all powered from the 12V by way of an additional 5V regulator on the motherboard. See how your composite video looks when you have the diskette drive unplugged.

Seconding what Mike said: 640 KB RAM with no sidecar means you have a third-party upgrade (such as a Jr Hotshot) plugged into the CPU socket under the disk drive.

[bloguidice]

Yes, it turns out that with the power to the disk drive removed, the composite video works. So it's odd, but I guess both systems have shorted drives somehow.

After removing the disk drive, the 640KB one does indeed have a JRHOTSHOT II in place. Does anyone happen to know if the PC Enterprise Memory Memory Software, jrConfig, which I got with the 512KB sidecar, will also work with the JRHOTSHOT II?

I did order a brand new disk drive (sealed), so should be able to get a fully working system. I also ordered a power sidecar, but I'm thinking that's not really necessary now. Anyway, if I get the 640KB system working, I may either sell the 128KB system or try and get a disk drive for that as well. We'll see.

Thanks again for all the help! I feel like I'm making real progress here.

[Gremlin5]

Both of your drives are by Qume, and I’ve found that these often need mechanical help as well. The clean-the-heads-and-rails routine is the least of it. If you get a drive that isn’t already known to be in working condition, it may not be able to spin a disk at the right speed or at all. (To fix that you’d need to lube the collet bearings, maybe the drive motor shaft, and maybe the spindle. You might need to adjust the drive belt tension or replace the belt. Then you’d check and tweak the motor speed as needed.) In contrast, the much-less-common Alps drives usually work without a fuss.

Odd I have acquired about 7 Qume142 drives and they have all worked perfectly. Maybe I shouldn't be saying anything or next time I try them they will all go up in a puff of smoke....