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External 720kb floppy drive on IBM 5160 XT

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Divarin

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Cleveland, OH
Hi all. I have an IBM 5160 XT. I recently picked up an IBM external floppy drive (720kb, 3 1/2") which connects to the floppy drive controller card via the pin connector on the card:
2eafbc372bee28940.jpg
I was unable to access it and I'm wondering if there's some setting I need to change, maybe add a jumper to the controller card?
I read through the manual for this computer and it did mention that dip switches 7 & 8 control the number of floppy drives but specifically the 5 1/4" floppy drives. I tried changing the dip switch settings to two drives anyway (switch 7 off, 8 on) but this did not let me access the drive. It did prevent dos from switching my existing 5 1/4" 360k internal floppy drive from A: to B: (as it does when you have one drive and you enter "B:") but there was no signs of activity on the external drive.

Also, I would like to open this up to clean the heads and lubricate the rails but don't see any screws? I assume there's some kind of clips that need to be ... un-clipped? But if anyone has any experience with these drives before I go smashing it and causing all kinds of cosmetic damage to the casing can you please enlighten me?
 
Chuck(G) said:
Where is your power supply for the drive? The 5160 floppy controller doesn't supply power.
Click to expand...

Hmm okay that would be a problem. The drive doesn't have any other connections on it besides the one cable so I assumed the power would go through that.
 
Probably. There were brackets with a 34 pin header and 4-pin Molex inside and a DC37F on the outside. The idea is that you'd daisy-chain the internal floppy connector to it, which would then supply power. Some third-part FDC cards, such as the Sysgen Omnibridge and the Micro Solutions Compaticard were equipped with jumpers to supply power.

I think that this may be a PS/2 device, however--and you're missing the bracket that provides power and floppy support.

That doesn't mean that you can't use it on your XT, so long as you figure out a way to get power to it.
 
Chuck(G) said:
Probably. There were brackets with a 34 pin header and 4-pin Molex inside and a DC37F on the outside. The idea is that you'd daisy-chain the internal floppy connector to it, which would then supply power. Some third-part FDC cards, such as the Sysgen Omnibridge and the Micro Solutions Compaticard were equipped with jumpers to supply power.

I think that this may be a PS/2 device, however--and you're missing the bracket that provides power and floppy support.

That doesn't mean that you can't use it on your XT, so long as you figure out a way to get power to it.
Click to expand...

Yeah looks like I'll have to open it up and see how to do that.
 
I recently went through this. On the DC-37 power pins are as follows:

1: +12V
2: 12V return
3: 5V return
4: +5V
 
If you want to make your 4865 "IBM original" you can add a pigtail to the DC shell using a 4-pin AMP Mate-N-Lok connector.
https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/172338-1/744764

That was the only difference between the XT and AT versions of this floppy drive. I did it by depinning the 4 power pins from the D-sub, stripping a bit of insulation, soldering on 4 conductors, heat shrinking them, and re-inserting the pins back into the DC-37. Then run your 4 wires out the back of the shell and crimp on the contacts for the mate-n-lok. The pinout is available here:
http://www.vcfed.org/forum/showthread.php?21470-Guide-4865-external-720k-drive-on-a-5160&p=147871#post147871
 
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