Tandon TM100-2 360K diskette drive Spindle Motor Shorted

[simmiv]

I've been restoring an Australian made IBM 5150 PC and recording my progress on youtube. In the second episode I discovered that one of the tow TM100-2 360K diskette drive has a shorted spindle motor. See here:

Just wondering if anyone knows where one can obtain a similar DC motor that is 12v and has the rotary encoder as well. I've measured the dimensions of it and following are a few photos of it.
It appears to be a 2,000 RPM motor based on the pulley dimensions and distance between them. I'm including a scope grab of a working drive for the encoder as well.. It appears to generate a sinus waveform with a frequency of 268Hz.



Just wondering what my optins are, i.e. getting a similar motor, rewind it or park it as a spare parts drive?

Rgds,
Simmi

 

[djg]

Just wondering what my optins are, i.e. getting a similar motor, rewind it or park it as a spare parts drive?

Done some work on motors but haven't had to deal with a shorted one. Now that you have the motor apart I would try to see exactly where the short is. That will give an idea on the effort needed to fix the motor. Did the short change with motor rotation?

 

[simmiv]

Done some work on motors but haven't had to deal with a shorted one. Now that you have the motor apart I would try to see exactly where the short is. That will give an idea on the effort needed to fix the motor. Did the short change with motor rotation?

Hi, yes I took it all apart and then measured across each commuter and they all measured short, or I should say about 8 ohms. Didn't matter which one to which one.. When looking at it, it doesn't look like it has any meltdown in the windings.. I haven't put it under a microscope yet, but I might do that to see if there are any signs of heat or shorts that I can't see with my eyes..

 

[Chuck(G)]

I did a spot check on my hellbox full of small brushed low-voltage DC motors and they tended to come in between 30-100 ohms. I then grabbed two known working TM100s off the shelf and check the motors (red and blue leads). Both came in between 55-60 ohms. Now, these were both TM-100-4Ms, but that probably has no bearing on the problem.

Did you check between the rotor laminations and the individual windings? Seeing all shorted is a bit unusual, unless there's been a breakdown in insulation.

 

[mark0x01]

Definitely check the commutator first. I have seen carbon buildup in the gap between the contacts cause issues.
Check with a meter and clean with something like a pcb cleaning wire brush.

 

[simmiv]

Thanks, I've checked the commutator and I can't see any dirt or shorts in there.. I've scrutinized the motor under a microscope and I can't spot anywhere where it might have overheated. It looks perfectly normal to me.. Measuring between the commutators gives around 4-5 ohms, which should be far higher.. It does have a grey, very hard blob on it, which I'm assuming was for rotational balance. Just attaching a few phtos.. I think I have tracked down a replacement, so I'm hoping to three of them, just in case..

 

[simmiv]

Just an update for those wanting to get a new spindle motor.. I have find a source for this motor in New Zealand. Alan from Casamodularsystems i.e. here.. has been very helpful and I managed to order and receive 3 spindle motors for the Tandon TM100 series.. Alan tells me he has more, plus has some more spareparts for older 8' drives. The only issue I had, which is worth knowing is the fact that you need to spend at least NZ $100 in order to be able to order and have it shipped overseas, which is understandable given the effort required to prepare, pack and send items interantionally. The site does have a range of other electronic items, so that wasn't an issue for me.. I hope this helps others in the same predicament.. Now I just need to fix up the drive!!