1050 Floppy Drive Rescue

[McFly88DMC]

Greeting all!  I've been working on a 1050 Floppy Drive that I recently picked up. It was listed as "working"...well, we know how that goes.  I was able to mostly revive it, but some puzzling issues remain. It passed several runs of the diagnostic disk, but failed once on the speed test.  It will work fine for a few minutes, then starts spamming "BOOT ERROR" after a while.  The heads have been cleaned.

 

What appears to be an inductor (L6) is really charred in the middle.  Any folks out there encounter anything similar?  I have no idea what value to replace it with...any pointers would be greatly appreciated.  I am currently working on replacing all of the electrolytic caps, the voltage regulators (7812 & 7805) and probably the belt if I can source one from Best.  Oddly it's missing the drive select switch (broken off?), so I'll pick one of those up as well.  

 

The drive itself is a World Storage unit, made in Hong Kong.  The power supply is a "Databyte" #DV-9034A rated for 9VAC @ 3.4Amps. Thanks!!

[xrbrevin]

im not familiar with WST 1050s but if it works ok for a while, it could be temperature related

do you have one of those laser thermometers? if so, zap it around when the problem arises. it might help narrow down the cause 🔫

[TGB1718]

1 hour ago, McFly88DMC said:

What appears to be an inductor (L6) is really charred in the middle.

If it is L6, then it's in series with the 12V power supply via Q6 to the spindle motor so if it's burnt, it may be just working

until it gets hot and then fails until it cools down again, not likely to last much longer, you need to replace it, it's value is 3.3uH.

 

[TZJB]

54 minutes ago, TGB1718 said:

If it is L6, then it's in series with the 12V power supply via Q6 to the spindle motor so if it's burnt, it may be just working

until it gets hot and then fails until it cools down again, not likely to last much longer, you need to replace it, it's value is 3.3uH.

 

I found the diagram. Maybe measure the voltage drop across the inductor to see if it is significant?

 

 

I wouldn't personally advise replacing the regulators with the same device as it won't give you any advantage, as with the capacitors unless they are obviously damaged or leaking. Atari original capacitors were over specified so are still servicable. Your PSU is also over specified for this device so is fine.

 

Rather than replace the drive select switches may I suggest extending them to the front right of the drive panel using small toggle switches for convenience? I use mine every day at the moment, switching between drive numbers at will.

 

 

Edited May 1, 2023 by TZJB

[McFly88DMC]

Thanks for the suggestions folks!

 

xrbrevin - I do not have one at the moment, but it's really something I should pick up.  It would come in handy for a variety of projects.

 

TGB1718 - Thanks for the inductor value, I couldn't find the darn thing anywhere in the service manual.  Is there a certain rating it should have? Watts/Amps etc?  I don't recall ever having had to replace one before.

 

TZJB - Thanks for the schematic, should be a big help tracing down the issue. 

 

Once I finish the caps, vr and inductor replacement I'll check voltages at the test points and see what happens.

 

[_The Doctor__]

Inductor heats up and then fails sounds plausible (its burnt and needs replacing), replacing caps is fine, also make sure to lightly lube all spindles and bearings.

Lastly, make sure all floppies spin easily in their jackets. Locked rotors spike everything.

After all of that is done you can set the RPM's etc.

 

Edited May 1, 2023 by _The Doctor__

[TGB1718]

2 hours ago, McFly88DMC said:

Is there a certain rating it should have? Watts/Amps etc? 

Had a quick look around and the lowest current rating I could find was 900mA, and the next one

was 3A, Q6 is a power transistor (max 4A), but obviously it's not pushing that much.

I've not got my 1050 open at the moment, so don't know if it has the current rating of the motor.

If it does say whet it's current rating is, should be easy to get the correct inductor, Ebay has loads.

 

Some of the I saw inductors have a power rating which is a bit odd as the resistance of inductors are very low

in the miliOhms region, so the DC voltage drop across them is tiny so just by Ohms law W=V Squared/R

or I squared*R so something must have happened in your drive to draw a ton of current to burn it like that.

 

 

 

 

 

 

 

[McFly88DMC]

Sorry for the lack of updates.  I've been busy with work and haven't been able to get back to this disk drive, but hopefully I can find a bit of time this weekend.

 

Doc - I'll make sure to check those things.  I did clean and lube the drive rails (thin film of Molykote EM-30L), as the drive must have been stored in a less than ideal environment.  I found several desiccated "stink bugs" and other funk/grime inside upon initial disassembly.  What's the best way to lube the spindles and bearings? 

 

TGB1718 - Much thanks for the info, I must admit I've not had much experience with inductors.  I checked the drive motor, but alas didn't seen any ratings on it.   

 

I've attached some pics of the WST mechanism for inquiring minds.  I'm a bit of a noob when it come to Atari 8-Bits, as I've only had my 800XL for a few months but have been very impressed with it.  It has the Wiztronics RAM upgrade and Supervideo 2.1 mod, and is really in nice shape for being 40?! years old.  I also have an AVG cart, which is just a brilliant piece of kit.  It's been a more than worthy addition to my menagerie of vintage computers and consoles.    

[TGB1718]

Did a bit of research on 5 1/4" drives similar to these, they require a max of 12V 1.2A for the unit.

Assuming it doesn't draw the max current and the supply will be split between the spindle

motor and the stepper motor, I would assume the spindle motor would be taking no more than

500mA.

 

[McFly88DMC]

TGB1718 - Thanks so much for looking into that!  I greatly appreciate it.

Does this inductor look like it will work for L6? https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B78108S1332K000/652542

 

I finished replacing the capacitors and regulators this morning.  I'm glad I did the caps, since several of the smaller ones had a bit of crust on the legs.  Swapped out the large "Wang's" capacitors for Nichicon PW's, and the smaller ones with Panasonic FM, Nichicon VZ and Nippon Chemicon KMG caps...should be good to go for many years.  Fresh L7812CV and L7805CV regulators as well.  If I have any more free time this weekend, I'll plug the drive mechanism back in and start testing voltages and such.  

 

Thanks again for the help folks!  I will keep you posted!

 

[macsonny]

On 5/2/2023 at 12:49 AM, TZJB said:

I found the diagram. Maybe measure the voltage drop across the inductor to see if it is significant?

 

 

I wouldn't personally advise replacing the regulators with the same device as it won't give you any advantage, as with the capacitors unless they are obviously damaged or leaking. Atari original capacitors were over specified so are still servicable. Your PSU is also over specified for this device so is fine.

 

Rather than replace the drive select switches may I suggest extending them to the front right of the drive panel using small toggle switches for convenience? I use mine every day at the moment, switching between drive numbers at will.

 

 

I really want to move my drive ID select to the front of the case. Can you share with us what you did?

[macsonny]

On 5/13/2023 at 11:53 PM, McFly88DMC said:

TGB1718 - Thanks so much for looking into that!  I greatly appreciate it.

Does this inductor look like it will work for L6? https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B78108S1332K000/652542

 

I finished replacing the capacitors and regulators this morning.  I'm glad I did the caps, since several of the smaller ones had a bit of crust on the legs.  Swapped out the large "Wang's" capacitors for Nichicon PW's, and the smaller ones with Panasonic FM, Nichicon VZ and Nippon Chemicon KMG caps...should be good to go for many years.  Fresh L7812CV and L7805CV regulators as well.  If I have any more free time this weekend, I'll plug the drive mechanism back in and start testing voltages and such.  

 

Thanks again for the help folks!  I will keep you posted!

 

I know this is a bit crazy but I've restored 4 x 1050 drives now (both types) and the most common issue I found with the drives was the felt pad on the drive head mechanism was worn out. Just make sure you spend a bit of time to replace these pads which are needed so the drive head applies just the right amount of pressure to the floppy surface.

 

I think you can buy them but I just made my own. Got a belt hole punch, some good quality felt from a local hobby shop and also some clear (and strong) double sided tape. 5 mins later I have replacement pads which work a treat and actually solved my problem for the drives in many cases.

 

Might not be an issue for you - but keep in the back of your mind.....................................

[TZJB]

13 hours ago, macsonny said:

I really want to move my drive ID select to the front of the case. Can you share with us what you did?

 

Yes, I just soldered 4 wires to the rear switches, 2 for each switch, and replicated the switches on the front panel using mini toggles to the right hand side of the front panel where there is space just for them!

 

 

This one also has a write protect switch on the left hand side and a triple OS switch in the LED hole. The write protect switch indicator is either green for protected or flashing red for unprotected so a power led is redundant.

[blacka013]

Hi TZB,

 

wouldbe very interested to see the 3 OS setup you have in the drive.

 

Regards

[TZJB]

4 minutes ago, blacka013 said:

Hi TZB,

 

wouldbe very interested to see the 3 OS setup you have in the drive.

 

Regards

 

It's a Lazer, Standard, USD using a centre off switch for Standard.

 

The circuitry is a standard Lazer with a 27256 EPROM instead of the 2764. I made the EPROM but did not engineer the upgrade.

 

TRI1050.ROM

[BillC]

It is possible to wire a DP4T(10 contact) slide switch as a replacement for the 2 single pole ID switches.

When wired correctly the IDs would be 1 thru 4 in order, it could also be done with a DP4T rotary switch but they are larger/more expensive.

 

https://www.digikey.com/en/products/detail/c-k/SS-24E06-TG-5-P/2747191

https://www.digikey.com/en/products/detail/cw-industries/G-141S-3011/9610

Edited May 17, 2023 by BillC

[TZJB]

1 minute ago, BillC said:

It is possible to wire a DP4T(10 contact) slide switch as a replacement for the 2 single pole ID switches.

When wired correctly the IDs would be 1 thru 4 in order, it could also be done with a DP4T rotary switch but they are larger/more expensive..

 

Do you have an installation we could see please? A slide switch is much harder to install than two toggle switches.

[BillC]

2 minutes ago, TZJB said:

 

Do you have an installation we could see please? A slide switch is much harder to install than two toggle switches.

No I don't, but the second switch linked in my earlier post has panel mounting screws, both could be glued in position from the inside.

While not as easy to install it does offer linear ID selection on a single switch.

[TZJB]

4 minutes ago, BillC said:

No I don't, but the second switch linked in my earlier post has panel mounting screws, both could be glued in position from the inside.

While not as easy to install it does offer linear ID selection on a single switch.

 

Each to his own. Toggle switches keep it simple, and I am not sure a slide switch on the front panel would work for me as it needs a bit of force and could disturb the drive. It would be less likely to break off though.

 

If anything I think I would prefer your rotary switch suggestion if it would fit, but then Atari never went for it...probably cost as you said.

[BillC]

37 minutes ago, TZJB said:

If anything I think I would prefer your rotary switch suggestion if it would fit, but then Atari never went for it...probably cost as you said.

The body of a rotary switch can be large as well and may be difficult to fit.

[McFly88DMC]

Hey all, I finally found some time to get back to this project.   I powered up the PCB without the drive mechanism attached and fortunately did not release any "magic smoke".  Checking the voltages on the power supply I am getting ~4.96V @ TP13, and ~11.6V @ TP14.  I picked up an infrared thermometer (Klein IR1) at xrbrevin's suggestion and did not notice anything out of the ordinary.  I will connect the drive mechanism and give it a run on my 800XL to see if I've gained any ground so far.  

 

I did reflow the solder joints on the SIO ports, TIP110, the rectifier diodes, and anything else that looked suspect to rule out any intermittent connections.     

 

macsonny - Thanks for the input!  My felt pad looks OK but I will take your advice and pick up/make a few spares just in case.

 

TZJB - That's a really good idea re: the switches if you use these drives frequently.  I have an AVGcart and only a handful of disks, so right now I'm just trying to restore this particular 1050 to stock for the sake of posterity.  If I find another unit on the cheap, I may get a little more adventurous with upgrades & tweaks >:)   

 

[McFly88DMC]

I reconnected the drive mechanism and decided to give it a whirl.  No fireworks/smoke/drama, and everything seems to be working again!  I ran the disk diagnostics several times and it passed each time.  I was able to format a fresh blank disk using an original DOS 2.5 disk, and subsequently duplicated DOS to the blank.  Voltages and temperatures seem to be as expected.  My only concern is the rectifier diodes...is it normal for them to heat up to around 150F (~65C)?  This is my first 1050, so not sure what to expect here.

I didn't notice the burnt L6 inductor heating up, so that's good.  If I don't hear back from anyone in the next day or so, I will just go ahead and order the one from digikey I linked to earlier.  On a side note, are inductors unidirectional?   

 

Thanks again so much for the advice everyone!  It's been an interesting journey for sure.  I've got some parts on order from Best & digikey to (hopefully) finish up this resto. 

[xrbrevin]

nice job! 🙃

those diodes do get hot - hence why they are elevated away from the PCB, by design

ive never measured the degrees of heat tho..

[TZJB]

2 hours ago, McFly88DMC said:

I reconnected the drive mechanism and decided to give it a whirl.  No fireworks/smoke/drama, and everything seems to be working again!  I ran the disk diagnostics several times and it passed each time.  I was able to format a fresh blank disk using an original DOS 2.5 disk, and subsequently duplicated DOS to the blank.  Voltages and temperatures seem to be as expected.  My only concern is the rectifier diodes...is it normal for them to heat up to around 150F (~65C)?  This is my first 1050, so not sure what to expect here.

I didn't notice the burnt L6 inductor heating up, so that's good.  If I don't hear back from anyone in the next day or so, I will just go ahead and order the one from digikey I linked to earlier.  On a side note, are inductors unidirectional?   

 

Thanks again so much for the advice everyone!  It's been an interesting journey for sure.  I've got some parts on order from Best & digikey to (hopefully) finish up this resto. 

 

That is great that it works again. Incidentally, the inductor can't be polarised as it's just a length of wire wound around a ferrite core. As it's still conducting it hasn't burnt out so you won't need a replacement. However, the diodes do warm up a bit, so don't put your fingers on them!

 

The drive select switches are just simple on/off switches to ground. Any switch will do, but without them the drive is set to ID D1:.

 

From SAMS:-

 

[McFly88DMC]

TZJB - Good to know re: the inductor.  I figured it was nonpolar like a resistor, but grateful for the confirmation.  Also, thanks for the schematic for the switches.  It may come in handy for me if I pick up another one of these drives in the future, and is a great reference for others!

 

The drive cleaned up really well too.  I'll have to throw some pictures up of the exterior later if I remember.