3.5" floppy drives

Hardware questions and modifications

3.5" floppy drives

Postby KenG » Thu Jul 28, 2016 5:49 pm

Elsewhere on this site Mike mentions using a 1.44MB drive in a PCjr using 720 diskettes and a device driver. I have a PCjr with a Quadram Drive Two on it. I would like to try this, but would need something to convert the 34 pin card edge connector on the cable to a 34 pin connector for the 1.44MB drive. I am fairly certain that none of them use the card edge connector. Anyone done this or know where I can get such an adapter? True 720K drives are insanely expensive so the savings on the drive could easily cover the cost of an adapter. Also I could get a fairly new drive that is likely to be much more dependable.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
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Re: 3.5" floppy drives

Postby geoffdaddy » Mon Aug 01, 2016 7:24 am

KenG wrote:Elsewhere on this site Mike mentions using a 1.44MB drive in a PCjr using 720 diskettes and a device driver. I have a PCjr with a Quadram Drive Two on it. I would like to try this, but would need something to convert the 34 pin card edge connector on the cable to a 34 pin connector for the 1.44MB drive. I am fairly certain that none of them use the card edge connector. Anyone done this or know where I can get such an adapter? True 720K drives are insanely expensive so the savings on the drive could easily cover the cost of an adapter. Also I could get a fairly new drive that is likely to be much more dependable.



AFAIK, only some very early 3.5" 720K drives used card edge connectors, those tended to be much taller mechanisms than the standard 3.5" form factor drives you typically find... not quite half height IIRC, but close.

Anyways, yeah, I have had some card edge to pin adapters in the past, so they do exist. Alternatively if you can't find one, you can get the 34-pin IDC pin connector you need and crimp it onto the ribbon cable carefully using a crimper or a bench vice if none is available.
PCjr: 10MB RACore 01 hard drive expansion, Hotshot 640kB RAM expander, optical mouse, Xircom PE3, speech sidecar.
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Re: 3.5" floppy drives

Postby Brutman » Mon Aug 01, 2016 10:30 am

I'm having a hard time keeping up on my mail lately, and forum posts are the first to suffer ...

There used to be adapters for this: http://www.floppyemulator.com/wp-conten ... _FDD_2.jpg

Also, cables that had both types of connectors at each position were common too.

I did not have a lot of success with 1.44MB drives. My memory is hazy, but it was related to booting or running diagnostics. It was as though the drive would default to high density mode and fail quickly. Booting from the 5.25" drive and using the 1.44 drive as a 720KB drive from DOS would work though.

Whatever drive you wind up with, be sure to use real 720KB/1MB diskettes (double density) not standard 1.44MB/2MB (high density diskettes).
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Re: 3.5" floppy drives

Postby KenG » Mon Aug 01, 2016 11:20 am

Thanks for the reply. I was able to find an adapter on eBay and have it ordered, along with a drive. Much cheaper and probably more reliable than getting a 720k drive. I plan on putting it in my Quadram Drive Two expansion chassis. I will use driver.sys to specify that it is a 720k drive. I will post my results here once I get everything and have a chance to test it.

I have a couple of other questions.

1) Any chance of getting a jr/IDE soon?

2) Anyone have the drivers for the Quadram/Racore/Rapport Drive Two expansion chassis? I would love to get the clock/calendar working!

I am trying to get a parallel CF reader working so I can download files using my Win 10 laptop and get them into the PCjr. Another member is sending me the drivers I need for that. This forum is great for those who want to mess with an old, unique computer. I was given the PCjr with power, parellel port, and two 128k sidecars. Might sell it off later, but plan to have some fun first.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
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Re: 3.5" floppy drives

Postby KenG » Thu Aug 18, 2016 9:02 am

Another question. Has anyone tried to interface a floppy drive emulator to a PCjr? I have seen articles here they have been used on old MACs and Amigas, so I would think it would be possible. You basically create a bunch of 720K folders on a flash drive and select which one is in use from the front panel of the drive. You then push the contents into a memory buffer that looks like a standard 720K floppy to the computer. Not the same as a hard drive, but might be better than the parallel port devices because you wouldn't have to load any drivers other than maybe driver.sys or drvparam. What do you think? I am working on getting a 3.5" drive working in my Quadram Drive Two. If that is successful, I might then buy one of these and try it.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
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Re: 3.5" floppy drives

Postby KenG » Fri Sep 09, 2016 7:54 pm

I finally scored an affordable 720k drive from eBay and received it today. It took me a while to get it working and even longer to figure out how to use drivparm to tell DOS that it was 720k and not 360. It works like I want it to now. Tomorrow I will install it in my Quadram Drive Two. This really opens up a lot to me as I have an old laptop with a 3.5" drive. Only the PCjr has a 5.25". I used driver.sys to set up the 5.25 as logical drive D and the 3.5 as logical drive E so I can use disk copy. Relearning DOS isn't easy.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
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Re: 3.5" floppy drives

Postby Vorticon » Mon Sep 19, 2016 2:46 pm

Another option of course is using an external 3.5" drive. I have the Backpack parallel port one and it works like a charm. Incidentally I also have the Backpack CD-ROM daisy chained to it and it also works great although it does not get much use... Found both on Ebay 3 or 4 years ago. The downside is that they are not bootable and require a driver, but they are great for software transfers between the Jr and more modern equipment.
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Re: 3.5" floppy drives

Postby PNKlett » Mon Sep 19, 2016 7:54 pm

This site has the whole kit.
http://abcresellers.com/store/product138.html

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Re: 3.5" floppy drives

Postby KenG » Wed Sep 21, 2016 5:47 pm

Good info, I paid at least twice that for a kit on eBay.
Enhanced PCjr with a jr-IDE (1GB DOM) and a parallel port side car with a compact flash reader and backpack 1.44mb floppy attached. Tandy video mod.
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