Pair of SIEMENS FDD 100-5 Floppy Drives

[Steven Feinsmith]

Hi everyone,

I recently acquired Heathkit H17 with a pair of Siemens FD100-5 drives from eBay. The seller stated it was a problem with non-power.

I received the H17 and checked the problem. Everything was intact and in clean condition. I disconnected power plugs from the floppy drives before I tested for power failure. I inspected the electrolytic capacitors, diodes, resistors, voltage regulators, and others, including PCB, to see if something was burned or loose due to bad soldering joints. Everything looks good, including the 1A slow blow fuse. I started to trace down what caused the power failure with my trustful Fluke model 289  multimeter. Bingo, the culprit was a faulty power switch. I bypassed the power switch, which is up and running generally with excellent voltage output. Also, I discovered the green wire for the ground was not attached to the chassis, which shows that the original builder forgot about it. I decided and pulled both floppy drives out from the chassis. I overhauled the chassis, including reformatting the capacitors, rebuilt them together, and ran tests in perfect condition.

Both Siemens FD100-5 floppy drives were dried completely. It's good that both drive belts are in excellent condition and look like new. The spindle hub shaft and R/W head movement were dried and not smooth, but the whole is still clean with very little dust. I decided to wait to power the drives for now until they need to have proper lubrication.

I recalled someone discussing the Siemens FD100-5 recently, but I accidentally deleted the messages and decided to ask you. I do not want to use WD-40 but seek silicon lube or lithium grease for both the head solenoid screw and spindle shaft. I like to disassemble the spindle shaft by removing the large spindle pulley. I removed the hex screw and washer, but the pulley and shaft seem unable to separate. I do not want to heat the shaft because some plastic may harm it. I wish to be more skilled in repairing the floppy drive. I further studied the floppy drive mechanism and showed it was not used much because it was not a sign of wear. I presume the whole chassis and floppy were only used a little by the previous owner.

I studied the OEM manual for the FD100-5 and discovered two bearings (I presume they are made of metal.) I realized I could easily remove the upper and lower ball bearings by removing C clips and then disassembling them for cleaning and lube before reassembling them. Should I use silicone lube or lithium lube for the bearings? As I mentioned above, do not use WD-40 because it is not an actual lubricant but a penetrating oil. It will destroy the bearings quickly.

I would like your advice before I can work on both drives to ensure they are smooth without resistance. I do not want to ruin both the drive belts because they are no longer replaceable. Also, my biggest fear was the lack of a head alignment diskette by Dysan. I am trying to figure out this situation. I have an MSO oscilloscope and frequency counter on my bench that can be used to test the drives.

Thank you,

Steven

[Mark Garlanger]

Hey Steven,

  You can still read/search for older messages on the list here: https://groups.google.com/g/sebhc even if you've deleted your copy of the email. Currently the FD100-5 thread, I think you are looking for, is just the third one on the list.

Mark

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[Glenn Roberts]

I will write up my notes on what I did.  Get back to you soon…

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On Oct 17, 2023, at 1:05 AM, Mark Garlanger <garl...@gmail.com> wrote:



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[glenn.f...@gmail.com]

This is from memory but here are the steps I took to clean each drive. Next time I do one I’ll take more pictures. These instructions are for the FDD 100-5 Siemens drive. The older Wangcos are quite similar and most of these steps would apply there too.

 

1. Remove the circuit board from the top of the unit via the four Phillips head screws.  You may find that one screw is longer. That one is designed to help hold the wire in place that goes to the read/write head. Carefully remove the connectors for the read/write head and the bottom edge of the board.
2. Remove the belt by rotating the pulley and gently nudging the belt off it. Set it aside so you don’t get oil or grease on it.
3. Working from the top of the unit, remove the E-clip retaining clip that holds in the pressure hub (white circular thing that presses down on the floppy disk). You should be able to remove that straight out the front opening of the drive. Remove the second E-clip that holds down the bearing. You should see a very small thin washer under the clip. Remove the washer and then pull out the black piece holding the bearing. Press the bearing out of the black part.
4. At the back of the drive remove the two 3/16” hex head screws securing the top bail portion of the drive hold down (the metal structure that closes on the disk). If your unit uses a connector for the LED you can clip the two cable ties, remove the connector (red is positive) and remove the whole bail mechanism. On older units the LED connection is soldered so just leave it in place but hanging loose.
5. Working from the bottom of the unit use an allen key to remove the screw retaining the flywheel from the hub. You should be able to just pull the flywheel off. If it gives you a hard time hold the top of the spindle and gently rotate the flywheel to release it.
6. You will now see the bearing on the bottom. Pull on the top part of the hub, the thing that looks like this:

 

7. Use that to push the ball bearing assembly out the bottom. Below the bearing you will find a 3-washer assembly: a very thin washer, a “wavy” washer, and another thin washer. Pull these out and set them aside

8. Pull the hub out the top including the top bearing. Slide that bearing off the hub. You should find another small very thin washer between the bearing and the top of the hub. Set that aside.
9. At this point you should have the three bearings. The two from the metal hub plus the one from the top pressure hub.

Soak these in kerosene, mineral spirits or your favorite degunker. Work the bearing races by hand or with a pencil inserted in the center until they move smoothly and clean. Use an air can to blow out the dirty oil.

10. Use a pinpoint oiler to insert some drops of oil and get the races running clean and smooth. Again, work by hand or with a pencil

11. This concludes the cleanup of the hub part. Next look at the stepper and worm gear. See if you can rotate the worm gear by hand. When it’s properly lubricated you should be able to slide the head mechanism back and forth and have it turn the worm gear, but you may not be able to do that at first.  You can insert oil where the worm gear goes into the motor and on the bearing at the other end. I used a light coating of white lithium grease (go sparingly) and just work the mechanism back and forth. Later when you run the disk drive tests the stepping function will help work this lubrication in. This is a tricky part because it’s hard to get your fingers in there to work the worm gear. You could possibly take this apart, but I tried to avoid that.
12. Next you need to lubricate the drive motor. The top part is easy as you can see the top of the motor spindle. Just put some drops of oil there. On the bottom there’s the brass pulley. With the unit on its side put some drops of oil in between the pulley and the motor – get them to go down so that they get to the motor shaft itself. Rotate the pulley/motor shaft by hand to work the oil in. later you’ll clean this up a but so you don’t get oil on the belt.
13. Now you need to reassemble things. Put the small thin washer on the hub spindle, then slide the bearing on and insert it back in place from the top of the drive. Next insert the spacer sleeve on the spindle:

And then the thin washer, wavy washer, thin washer and finally the second bearing. Reattach the flywheel using the allen screw. Spin the flywheel. The wheel should spin freely and rotate many times before it slows.

14. Reattach the bail on the top of the drive. Reattach the leads to the LED (red is ‘+’) and secure them at the two locations where they were originally secured using small cable ties. Be sure not to trap the black piece that holds the pressure pad for the read/write head. Hold that up and out of the way while securing the bail.
15. Reassemble the top pressure hub by inserting the bearing into the black part (the flange will allow it to only go one way), then place the large spring, and the black part onto the shaft inserted up through the white nylon pressure hub. Place the thin washer on top and secure things with the E-clip. Place the smaller spring on top of that and insert through the front of the drive placing this assembly into the drive. Close the drive cover and then install the second E-clip to secure the pressure hub in place. With the drive cover closed, spin the flywheel to ensure that things rotate smoothly.  It should spin freely for several turns before slowing down.
16. Now is a good time to clean the head. Hold the spring-loaded pressure pad arm up and out of the way and use alcohol and a swab to clean the head. Inspect the pad to make sure it is in place and functional.
17. Working from the bottom, use a cotton swab with alcohol to clean any dirt or oil from the brass pulley and the flywheel. Gently reinstall the belt by putting it over the brass pulley and rotating the fly wheel to get the belt on track.
18. Reinstall the circuit board on top of the drive using the four screws. The longer screw goes where the read/write head cable is to help hold it in place. On the Siemens drives the connectors are tinned so its best to squirt some deoxit contact cleaner on the pins and work the connectors back and forth to clean the contacts.

 

I think that’s it. Following these steps I would install the appropriate jumper header and put the drive in a bootable system and run INIT to try and create a disk. Only the last drive in the chain should have the terminator resistor installed.  If INIT succeeds then run TEST17 and test the stepping rate (it should step down to about 16 ms or better). Then do a media check.  If all that works you can run the full general drive checkout.  If you have problems  you may need to use the XRSIZR program that Terry posted here to dig deeper…

 

• Glenn

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[Joseph Travis]

I have two comments to add:

1.  Don't over lubricate!

2.  Before testing R/W operation, insert a hard sector disk and at the H: prompt, enter G(o) 7372 <RETURN> to execute the drive speed routine.  The value shown is in octal.  Adjust the potentiometer on the motor controller board so the number displayed is 177-200.

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[Glenn Roberts]

Right. On the h8 use either TEST17 or XRSIZR to set the speed. Rotate the trimpot back and forth a little bit a few times first to clean the wiper, then set the speed. XRSIZR lets you set this quite precisely.

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On Oct 17, 2023, at 9:12 AM, Joseph Travis <jtravi...@gmail.com> wrote:



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[Steven Feinsmith]

I appreciate the information you provided me. It will be a sure way to help me restore the Siemens FD100-5. I have a total of five same models of drives. One each was from my Heathkit H88 and H89. One was from Heathkit H77 and two from the H17 enclosure. I discouraged two had worn out belts and needed to have the replacement. For many months, I have been trying to find an exact match. There were no available anywhere.

I look forward to seeing more pictures from you.

Thank you very much,

Steven

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