360Kb DSDD Floppy Drive Wanted

[Stone]

Or should we start talking about bad electrolytic condensors? :wink:

I'm game.

I've got a dead socket 7 motherboard with two 6.3v 2200uf caps with swollen tops. Is it worth, IYHO, stealing two of the same (w/flat tops) from another, really dead board or should I try to locate two new ones somewhere. I have no idea where to get these so I was thinking of cannibalizing something in worse shape.

 

[bettablue]

Bettablue, I'm assuming that you are aware that you need to tell a 5150 how many floppys you have, i.e., 1, 2, 3 or 4... via one of the little blue switch blocks on the motherboard. It's really a dumb, little bastard and you have to tell it nearly everything.

Yeah. I have the 5150 configured properly. In fact I just ran a diskcopy and tried to run chkdsk. That failed in drive "B", but in drive "A" it read OK. That tells me that my drive B is still out of alignment somewhere. It won't reliably read several disks that it creates, but those same disks will read just fine on my A drive.

I'm going to swap out my "B" drive with my spare Tandon. The drives that came in my 5150 were both pretty dirty and in need of work. So they were cleaned and alligned and when they arrived, were immediately installed back into the 5150. So, I'll see what happens when the Tandon is installed. Then my "B" drive will be sent out to be checked and realigned if necessary. I doubt very seriously that it's out by much, and since it was only a while ago, and I keep the drive openings covered when not in use, I also doubt that there will be any need for a cleaning.

It also appears that I need to check some of my parallel port configurations in my 5150 too. But I'll look through the tech ref manual for those settings.

 

[bettablue]

O, I swapped out the secondary drive. Aside from my backup being a little noisier, it seems to be working just fine. Disks I write from the "A" drive work perfectly and disks I write from my Compaq are also working fine. Then my DOS diskettes all work fine in all of the drives I have installed, so the whole time, the problem has been with my "B" drive.

Again, I'm sorry to have dragged all of you through my mess. But at least now I know what I need to do.

 

[tezza]

Amen.

As to Tez's comment that it's the OS and not the controller that determines whether you can use double-sided disks, there's no way that a single-sided controller can write on the second side of a DS drive (unless you flip it over or manually switch sides ;-))

True. But in the context of the conversation I wasn't meaning all floppy disk controllers. I meant that the floppy disk controller that was normally sold with the TRS-80 Model 1 expansion unit (and my System 80 expansion unit) supported double-sided (and 80 track) operations assuming that you also had the OS, drives and disks to support it.

Tez

 

[Chuck(G)]

I'm game.

I've got a dead socket 7 motherboard with two 6.3v 2200uf caps with swollen tops. Is it worth, IYHO, stealing two of the same (w/flat tops) from another, really dead board or should I try to locate two new ones somewhere. I have no idea where to get these so I was thinking of cannibalizing something in worse shape.

Don't bother stealing old caps--it's like replacing light bulbs with old ones. It may work for awhile, but you're going to be back soon.

Check eBay for sellers. Re-capping seems to be a popular pastime nowadasy. Chinese sellers have lots of cheap offerings. Just search on "2200* capacitor". Go with the Panasonics, Nichicons or Rubycons or Nippon Chemi-con; unless they're forgeries, those brands are pretty reliable.

 

[Druid6900]

True. But in the context of the conversation I wasn't meaning all floppy disk controllers. I meant that the floppy disk controller that was normally sold with the TRS-80 Model 1 expansion unit (and my System 80 expansion unit) supported double-sided (and 80 track) operations assuming that you also had the OS, drives and disks to support it.

Tez

OK, the way this worked is like this.

The original cable for the Model I drives were "keyed" for drive position by removing different pins on the connector for each drive position. TRSDOS never asserted the side signal because all the drives were supposed to be SS/SD. However, if you used a fully pinned connector, other Model I operating systems could assert the side select signal and would see the first DS/SD drive as drives 0 and 1 and a second DS/DD drive as drives 2 and 3.

TRSDOS would still only see 2 SS/SD drives though.

 

[MikeS]

OK, the way this worked is like this....

Thanks for clearing that up; so even the original controller had provisions for switching the heads even though it wasn't originally implemented, and even when it was it was sort of like a manual switch instead of a 'true' DS implementation. Interesting.

 

[tezza]

OK, the way this worked is like this.

The original cable for the Model I drives were "keyed" for drive position by removing different pins on the connector for each drive position. TRSDOS never asserted the side signal because all the drives were supposed to be SS/SD. However, if you used a fully pinned connector, other Model I operating systems could assert the side select signal and would see the first DS/SD drive as drives 0 and 1 and a second DS/DD drive as drives 2 and 3.

Hmm. Are you sure this is as far as it could go in the Model 1 though? In my Model 1 clone, an advanced Model 1 DOS (e.g. Newdos 80 ver 2) could not only use DS drives with a fully pinned connector, but both sides were treated as the one disk (as you would want them to be). My original setup had a 40track single sided drive as drive 0 and an 80 track double sided drive as drive 1.

Are you sure a Model 1 couldn't do this also? From memory both the IE on the Model 1 and the IE on my System 80 used the same controller (Western Digital FD 1771)? Of course it could be that my clone had some extra circuitry to beef up the disk interface but I didn't think this was (is) the case.

Tez

 

[Chuck(G)]

Here's a follow-up on the mysterious "single sided" CDC (77744401) drive. On a quick inspection (rule: always look at what you have to do before picking up the screwdriver!) I noted a pin-and-weight affair connected to the head carriage. On closer inspection, it turned out to be covered with solidified grease that glued the weight firmly to the base and a pin (which slides through the weight) firmly glued immobile in the weight. As a result, one end had become detached from its post on the head carriage:

The grease was worse than cold tar and had actually reacted with the metal of the weight and frame to make a black goo and did not yield to mineral spirits, alcohol or perc. MEK did the trick and the whole affair left soaking overnight eventually freed the pin from the weight. I cleaned everything up and applied some white lithium grease, which appears to work just fine. The ends of the pin were secured with a drop each of lacquer.

The drive appears to be 100% and reads my disks, but I haven't done an alignment check yet. If it's close, I'll just leave it alone.

 

[bettablue]

This was something I had mentioned in one of my previous postsbut in that case, that weight had fallen out of the drive. I still held onto it though. However, the funny part about all this is that my primary floppy drive has been working perfectly without it. Still after reading this and other posts, I'll be reinstalling it after cleaning the drive of the old grease. Then I'[ll follow this advice on cleaning and sealing the weight in place.

The drive in question here is probably one I sent to Chuch to see why it would not read larger disk images on 350 Kb diskettes. In other words, once the read operation reached a certain point, even though there was still sufficient space on the diskette, the drive would fail to read.

Once I get the drive back from Chuck, I'll have the other one ready to re-install as well.

Here's a follow-up on the mysterious "single sided" CDC (77744401) drive. On a quick inspection (rule: always look at what you have to do before picking up the screwdriver!) I noted a pin-and-weight affair connected to the head carriage. On closer inspection, it turned out to be covered with solidified grease that glued the weight firmly to the base and a pin (which slides through the weight) firmly glued immobile in the weight. As a result, one end had become detached from its post on the head carriage:

The grease was worse than cold tar and had actually reacted with the metal of the weight and frame to make a black goo and did not yield to mineral spirits, alcohol or perc. MEK did the trick and the whole affair left soaking overnight eventually freed the pin from the weight. I cleaned everything up and applied some white lithium grease, which appears to work just fine. The ends of the pin were secured with a drop each of lacquer.

The drive appears to be 100% and reads my disks, but I haven't done an alignment check yet. If it's close, I'll just leave it alone.

 

[Chuck(G)]

I think this thing serves to damp a vibration problem in the mechanism or possibly a stepper issue (if you step fast enough on most steppers, the directionality is lost and the direction can reverse without some sort of momentum). The heavy grease (and I may replace the lithium with a heavier bearing grease) would certainly confirm this. That's why I want to keep the drive for a few more days to hammer on it to see if I can see any problems with the setup.

It's odd--I have other CDC/MPI floppy drives that don't have this little "feature".

 

[bettablue]

I appreciate the effort. When you're done, please include any additional instructions to follow with my other drive, and what you would consider a routine maintenance scedule.

I'll be waiting.

I think this thing serves to damp a vibration problem in the mechanism or possibly a stepper issue (if you step fast enough on most steppers, the directionality is lost and the direction can reverse without some sort of momentum). The heavy grease (and I may replace the lithium with a heavier bearing grease) would certainly confirm this. That's why I want to keep the drive for a few more days to hammer on it to see if I can see any problems with the setup.

It's odd--I have other CDC/MPI floppy drives that don't have this little "feature".

 

[bettablue]

You know Chuck? Once the drive get's back to me, I'm definitely going to look at my other two. I know one has this weight, while I'm not too sure about the other. But all three are identical.

Funny thing though is that I believe you're right in another aspect too. In the 5150 I rebuilt for my friend here in Las Vegas, he again has the same exact drive, and the weight is not there. The holes are there, and it is pretty clear that there was something there at one point, but the weight isn't there any longer. His drive also has issues with large disk read operations on 360Kb diskettes. However, the 180Kb disks, everything seems fine. So his drive is doing exactly what mine was.

Oh well. I know it may be a bit to ask, but I think it's impotant here for consistancy sake. When you are finished lubing the weight track, can you somehow put some of the same grease you used into a small container? That way, when I get into replacing the one drive and cleaning the other, I'll have both of my drives lubed itentically. Don't forget to let me know how much I owe.

Thanks again Chuck.

I think this thing serves to damp a vibration problem in the mechanism or possibly a stepper issue (if you step fast enough on most steppers, the directionality is lost and the direction can reverse without some sort of momentum). The heavy grease (and I may replace the lithium with a heavier bearing grease) would certainly confirm this. That's why I want to keep the drive for a few more days to hammer on it to see if I can see any problems with the setup.

It's odd--I have other CDC/MPI floppy drives that don't have this little "feature".