polishvito wrote on 2023-01-04, 12:45:

I tried recapping one of the drives but same behavior. Cleaned the drive heads as well.

Did you recap both PCBs, or only the main one? The drive has a second PCB that controls the spindle motor. I had a PS/2 Model 30 drive where the cap on the motor PCB failed, causing the drive to run at erratic high speeds. See my thread Let's fix some PS/2 floppy drives! for a diagnostic program you can enter in ROM basic to test the rotational speed of a PS/2 model 30 drive.

Yeah would replace all the caps if it were me. One thing I never understood after owning a 5150+3270 is why IBM decided to change everything going into the ps/2 line (non-standard near everything compared to the previous), think that was their downfall and started the beginning of the clone wars, which were so much better in many ways at that time.... jmho.

mkarcher wrote on 2023-01-04, 23:17:

polishvito wrote on 2023-01-04, 12:45:

I tried recapping one of the drives but same behavior. Cleaned the drive heads as well.

Did you recap both PCBs, or only the main one? The drive has a second PCB that controls the spindle motor. I had a PS/2 Model 30 drive where the cap on the motor PCB failed, causing the drive to run at erratic high speeds. See my thread Let's fix some PS/2 floppy drives! for a diagnostic program you can enter in ROM basic to test the rotational speed of a PS/2 model 30 drive.

Your post and your diagrams are phenominal, thank you.

So, no I didn't recap the second PCB just the main one. So I took the drive apart and recapped. I tried to be as careful as possible but it seemed real easy to lift the pads when taking those fuckers off. I don't know if it has to do with leakage that weakened the board underneath or what. So I replaced the caps with electrolytic ones. There was a damaged trace coming off of C1 to R50 but I put a bodge wire in. Based on your schematic I verified everything from the new capacitors is going where it should be going. Unfortionately the drive still does not work - and from what I can tell the motor isn't even trying to spin up. The light comes on and there is a brief noise from inside, but I don't see the motor even trying to spin. My B: drive that had the similar failings from this machine at least tries to spin the motor, even if it doesn't read anything.

So... yeah I've managed to make it worse. I rechecked every connection off these capacitors with a multimeter and there seems to be continuity where there should be.

Really stuck with this drive at this point. Any thoughts about what to look at next?

Plus none of this explains why using a known good FD with an adapter to standard connectors doesn't work either.

polishvito wrote on 2023-01-06, 18:52:

The light comes on and there is a brief noise from inside, but I don't see the motor even trying to spin. My B: drive that had the similar failings from this machine at least tries to spin the motor, even if it doesn't read anything.

So... yeah I've managed to make it worse. I rechecked every connection off these capacitors with a multimeter and there seems to be continuity where there should be.

Really stuck with this drive at this point. Any thoughts about what to look at next?

Generally: For the motor to turn, the motor controller IC needs to have supply voltage (+12V), /EN (pin 31) grounded, EN (pin 24) high, all three hall inputs Hu/Hv/Hw working and all three drive phases (U/V/W) connected. The hall inputs only work if the hall sensors are supplied. The suppy for the hall sensors is generated from U2E and U2F., which is powered by +5V. If you have a meter, you should be able to probe for the supply voltages, the /MTR_ON signal and the hall sensor supply at R1/R4.

In your case: You might want to start checking for issues you might have caused by the rework, e.g. a short between R2 and C50.

You can adjust the RPM measurement program to use Drive B: instead of Drive A: by replacing &H1C by &H2D in BASIC line 20. You can also just keep the floppy motor enabled by executing lines 10 and 20 to turn on the motor, and then repeatedly executing line 1010. No need to type all the other lines.

polishvito wrote on 2023-01-06, 18:52:

Plus none of this explains why using a known good FD with an adapter to standard connectors doesn't work either.

Indeed. Did you see the note "Cut JP1 for Model 25 or 30 if issues occur" on the adapter? I don't know how the adapter is designed, so I can't tell you whether cutting the jumper solves your current issue, though.

mkarcher wrote on 2023-01-06, 22:54:

Generally: For the motor to turn, the motor controller IC needs to have supply voltage (+12V), /EN (pin 31) grounded, EN (pin 2 […]
Show full quote

polishvito wrote on 2023-01-06, 18:52:

The light comes on and there is a brief noise from inside, but I don't see the motor even trying to spin. My B: drive that had the similar failings from this machine at least tries to spin the motor, even if it doesn't read anything.

So... yeah I've managed to make it worse. I rechecked every connection off these capacitors with a multimeter and there seems to be continuity where there should be.

Really stuck with this drive at this point. Any thoughts about what to look at next?

Generally: For the motor to turn, the motor controller IC needs to have supply voltage (+12V), /EN (pin 31) grounded, EN (pin 24) high, all three hall inputs Hu/Hv/Hw working and all three drive phases (U/V/W) connected. The hall inputs only work if the hall sensors are supplied. The suppy for the hall sensors is generated from U2E and U2F., which is powered by +5V. If you have a meter, you should be able to probe for the supply voltages, the /MTR_ON signal and the hall sensor supply at R1/R4.

In your case: You might want to start checking for issues you might have caused by the rework, e.g. a short between R2 and C50.

You can adjust the RPM measurement program to use Drive B: instead of Drive A: by replacing &H1C by &H2D in BASIC line 20. You can also just keep the floppy motor enabled by executing lines 10 and 20 to turn on the motor, and then repeatedly executing line 1010. No need to type all the other lines.

polishvito wrote on 2023-01-06, 18:52:

Plus none of this explains why using a known good FD with an adapter to standard connectors doesn't work either.

Indeed. Did you see the note "Cut JP1 for Model 25 or 30 if issues occur" on the adapter? I don't know how the adapter is designed, so I can't tell you whether cutting the jumper solves your current issue, though.

Yes I saw the note for cut JP1 for Model 25/30, however I could not find out what that actually does, if it will prevent me from using the adapter in the future with other non model 25/30s, so I was hesitant to cut it.

Still no luck with the drive I repaired. So I did the reasonable thing and said fuck it, and took the second drive apart. This time I recapped just the motor PCB not the controller one. The caps obviously had leaked. Man am I really just this bad at desoldering these surface mount components or is it the board and the corrosion? It seemed very easy to lift the pads and traces up even with being as careful as I possibly could. Granted this is me with a soldering iron and wick, I don't have an actual desoldering station.

However, by some minor miracle, THE DRIVE WORKS!!! I was able to run the reference disk and set the date/time to get rid of the error codes. I tried out some other software and everything WORKS!

This probably doesn't seem like much to many of the more experienced members here, but for a complete novice like me this was my Tom Hanks I HAVE MADE FIRE castaway moment. I'm super pumped that I have one working drive.

I'll keep tinkering with the other one, but I can live without it. Two drives on this machine certainly isn't necessary for me.

polishvito wrote on 2023-01-08, 23:08:

Still no luck with the drive I repaired. So I did the reasonable thing and said fuck it, and took the second drive apart. This time I recapped just the motor PCB not the controller one. The caps obviously had leaked. Man am I really just this bad at desoldering these surface mount components or is it the board and the corrosion? It seemed very easy to lift the pads and traces up even with being as careful as I possibly could. Granted this is me with a soldering iron and wick, I don't have an actual desoldering station.

Old boards, especially with damage from leaking capacitors or Nickel rechargable batteries are easy to damage when you try to rework them.

An issue with desoldering SMD components is that unlike with leaded through-hole components, you can't just desolder one leg, bend it out and desolder the other leg later. Moving an SMD cap with only one pad heated will put a lot of stress on the other pad. You can try to heat both sides one-after-the-other until both are (nearly) molten and try to very carefully move the component while still heating both pads, one after the other. Or, if you can get a cheap second soldering iron (the 20 buck class should be good enough for this), use that one to keep the second pad hot when you use your primary soldering iron to melt the first pad.

Anyway, congratulations to your first fixed drive!

mkarcher wrote on 2023-01-09, 18:49:

Old boards, especially with damage from leaking capacitors or Nickel rechargable batteries are easy to damage when you try to re […]
Show full quote

polishvito wrote on 2023-01-08, 23:08:

Still no luck with the drive I repaired. So I did the reasonable thing and said fuck it, and took the second drive apart. This time I recapped just the motor PCB not the controller one. The caps obviously had leaked. Man am I really just this bad at desoldering these surface mount components or is it the board and the corrosion? It seemed very easy to lift the pads and traces up even with being as careful as I possibly could. Granted this is me with a soldering iron and wick, I don't have an actual desoldering station.

Old boards, especially with damage from leaking capacitors or Nickel rechargable batteries are easy to damage when you try to rework them.

An issue with desoldering SMD components is that unlike with leaded through-hole components, you can't just desolder one leg, bend it out and desolder the other leg later. Moving an SMD cap with only one pad heated will put a lot of stress on the other pad. You can try to heat both sides one-after-the-other until both are (nearly) molten and try to very carefully move the component while still heating both pads, one after the other. Or, if you can get a cheap second soldering iron (the 20 buck class should be good enough for this), use that one to keep the second pad hot when you use your primary soldering iron to melt the first pad.

Anyway, congratulations to your first fixed drive!

Very interesting idea. How are you actually removing the component though, seems like you need three hands - two for the irons and one to pull on the cap?

polishvito wrote on 2023-01-10, 15:06:

Very interesting idea. How are you actually removing the component though, seems like you need three hands - two for the irons and one to pull on the cap?

No third hand. Use the two irons as tweezers to pick up the component. Of course, this also exists as professional tool, called "desoldering tweezers".

mkarcher wrote on 2023-01-10, 18:57:

polishvito wrote on 2023-01-10, 15:06:

Very interesting idea. How are you actually removing the component though, seems like you need three hands - two for the irons and one to pull on the cap?

No third hand. Use the two irons as tweezers to pick up the component. Of course, this also exists as professional tool, called "desoldering tweezers".

After some research I ended up ordering one of these hot air stations: https://www.amazon.com/dp/B08VNYPL7H?psc=1&re … product_details

Seems to have decent reviews, and with the coupon it's going for $40 right now so figured it was worth a try. If all goes well hopeful this will make taking those surface mount components off easier.

polishvito wrote on 2023-01-13, 15:29:

mkarcher wrote on 2023-01-10, 18:57:

No third hand. Use the two irons as tweezers to pick up the component. Of course, this also exists as professional tool, called "desoldering tweezers".

After some research I ended up ordering one of these hot air stations: https://www.amazon.com/dp/B08VNYPL7H?psc=1&re … product_details

Seems to have decent reviews, and with the coupon it's going for $40 right now so figured it was worth a try. If all goes well hopeful this will make taking those surface mount components off easier.

A hot air station is definitely more versatile than SMD desoldering tweezers. For example, you can easily desolder SMD ICs using that hot air station. On the other hand, for the specific use case of desoldering two-connector SMD components like resistors, capacitors, inductors and diodes, the tweezers can apply heat even more localized than a hot air gun. So if you end up removing this kind of components a lot, tweezers might be an interesting addition. For normal SMD rework usage, buying a hot air station is a good idea, and if that specific station is any good (I don't have first-hand experience with hot air yet) it will make working on SMD stuff easier than trying to use a soldering iron.

Even with a hot-air station, for soldering (in contrast to de-soldering) SMD ICs, you might want to practice drag soldering (check youtube for tutorial videos) with a classical iron. Unless you work with paste and stencil, it might work better than using hot air, as drag soldering (if performed well) automatically applies an appropriate amount of solder to the pins.

mkarcher wrote on 2023-01-13, 19:15:

polishvito wrote on 2023-01-13, 15:29:

mkarcher wrote on 2023-01-10, 18:57:

No third hand. Use the two irons as tweezers to pick up the component. Of course, this also exists as professional tool, called "desoldering tweezers".

After some research I ended up ordering one of these hot air stations: https://www.amazon.com/dp/B08VNYPL7H?psc=1&re … product_details

Seems to have decent reviews, and with the coupon it's going for $40 right now so figured it was worth a try. If all goes well hopeful this will make taking those surface mount components off easier.

A hot air station is definitely more versatile than SMD desoldering tweezers. For example, you can easily desolder SMD ICs using that hot air station. On the other hand, for the specific use case of desoldering two-connector SMD components like resistors, capacitors, inductors and diodes, the tweezers can apply heat even more localized than a hot air gun. So if you end up removing this kind of components a lot, tweezers might be an interesting addition. For normal SMD rework usage, buying a hot air station is a good idea, and if that specific station is any good (I don't have first-hand experience with hot air yet) it will make working on SMD stuff easier than trying to use a soldering iron.

Even with a hot-air station, for soldering (in contrast to de-soldering) SMD ICs, you might want to practice drag soldering (check youtube for tutorial videos) with a classical iron. Unless you work with paste and stencil, it might work better than using hot air, as drag soldering (if performed well) automatically applies an appropriate amount of solder to the pins.

Thanks for the tips.

I bought a practice SMD board like this to gain some more experience:

Also have some old cards I can practice on (dial up modems I doubt anyone will miss). After I get some use out of that hot air station I'll give some feedback on it.

Just an update, that hot air station is a game changer. Works great for 40$, plus came with a set of fine tip tweasers which are better than what I was using.

Managed to put together that practice board.

I also got two more 720K model 30 drives off ebay sold in non working condition. Was able to recap one and make it work. Second one had it's own issues bedsides the caps, the edge connector had a part broken off and one of the heads was missing, but I was able to remove the motor board and transplant it into my original nonworking drive. So now I ended up with 3/4 working 720K drives. Not too shabby.

Even with a hot air station, and good tweasers, and a lot of patience, still had a little bit of pad lifting and had to do a bodge wire for once trace - those things are fragile.