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wrljet
May 19th, 2010, 01:49 PM
I have the floppy controller from a 5150 I'm restoring, with the wide bracket.
P/N 1809113. It uses an Intel 8272 controller chip instead of the uPD765 found on my XT controllers,
along with some custom IBM "cans" that look like what they used in the 370 mainframes.

Does anybody have the schematic for this earlier board?
All I have is PC Tech Ref 2.02 and it shows the later board.

Pic below shows the PC board (top) vs. the XT board (bottom).

A larger version of the image is at:
http://www.wrljet.com/rennpics/PCXT-Diskette-Adapters.jpg

Thanks, Bill

http://www.wrljet.com/rennpics/PCXT-Diskette-Adapters-800.jpg

per
May 19th, 2010, 03:05 PM
Since large parts of the PCB's are identical, I assume that the custom IBM chips are just the 5 TTL chips on the lower left (XT from the version) combined into some custom chips. As for scematics, I don't really think there are any huge differences except for that.

mikey99
May 19th, 2010, 03:06 PM
Wow, I never realized there were any differences in the diskette adapters, will need to dig through
my parts boxes and see which ones I have :-)

Chuck(G)
May 19th, 2010, 03:31 PM
If no one else has it, I have the schematics for the old one. The primary difference is in the data separator--the old uses some IBM hybrid circuits to form a PLL data separator; the new one uses some flip-flops and a MC4044 phase detector and a MC4024 VCO to accomplish the same. IMOHO, the old separator is by far the better one and the new one mostly a cost-reduction measure (it could be that IBM lacked the production capability for the hybrid devices in quantity). Later versions of the controller used a WD9216 data separator.

I replaced the 8272 on mine with a NEC uPD765AC. If you've got an 8272A, you're okay--they're basically the same. But the non-"A" 8272 has a very long (1 msec.) "blind spot" after index that can create problems with disks made on non-IBM systems.

Why do you need the schematic? You're not going fix the hybrid parts--there's almost no documentation on them. Mostly boxes with numbered pins.

wrljet
May 21st, 2010, 02:43 PM
I'm looking for the schematic because I'm trying to get a remote floppy running off the 37-pin connector
and things aren't what I'm expecting.

And I'd like to know what's on P3.

Bill

Chuck(G)
May 21st, 2010, 03:08 PM
The DC37 has exactly the same pinout as the Rev. 2 one. Namely: 1-5: NC 6: Index 7: Motor enable C 8: Select D 9: Select C 10: Motor enable D 11: Direction 12: Step 13: Head select 14:Write gate 15: Track 0 16: Write protect 17: Read data 18: Write data 19: NC 20-37: Ground

Or, if you take a normal drive ribbon cable and crimp it into a DC37 IDC connector with position 34 of the ribbon cable in the pin 19 position of the DC37, you'll have it.

As far as P3, the 16MHz XCO is divided by 2 by section 1 of U2, 74LS109 JK FF. Pin 3 of P3 is connected to pin 5, PRESET* of the FF; pin 4 is connected to pin 1, CLEAR*. Both 3 and 4 are pulled high by 2 sections of RP2 (2K each). The idea is that you can drive pins 3 and 4 of P3 with an external clock and its complement for testing.

wrljet
May 22nd, 2010, 06:58 AM
Thank you, Chuck, for the information. I now have the 4869 external drive jumpered to work on the 5150.

Do you recommend replacing that 8272 non-A?

Bill

Chuck(G)
May 22nd, 2010, 08:07 AM
You should have mentioned that you were working with a 4869--I've got a bunch of them here and have done the pair swap at the drive connector many times--so much so, that I have a method for using packing tape and working only by pair color to do it and re-use the original connector.

I do recommend replacing the original 8272 with either an "A" part or one of the NEC 765AC parts (or any one of the equivalents from other vendors). The 8272 was a bit buggy in addition to having some timing issues and the original diskette adapter was the only one to use it. And I'd recommend just installing a 40-pin socket, so that if you ever wanted to go back to the original, it would be very easy.

wrljet
May 22nd, 2010, 08:14 AM
Chuck,

I didn't change the cable. I soldered a wire to the motor enable pin on the resistor pack, and wire wrapped that to the select jumper, and changed the select jumper from 1, to 0. One reason I wanted the schematic was to make sure nothing bad was going to happen.

It's working well.

Pic:
http://www.wrljet.com/rennpics/4869-mod.jpg

Bill

Chuck(G)
May 22nd, 2010, 08:41 AM
I wanted something that would work with any drive; even a 3.5-5.25 dual drive, so reworking the connector was most expedient for me. If I jumpered the drive, then I'd have to remember that the next time I swapped a drive in the box.

k2x4b524[
May 22nd, 2010, 12:54 PM
finding this thread, i am going to ask, i have one of those 4869s and it refuses to work, i replaced the ALPS drive with a mitsumi one as the ALPS failed, but the mitsumi refuses to work on my 5160's or my 5150. I'd like to be able to slap a 720kb in this sucker and be able to use it with my 5150. Is this even possible? or do i need to do that little jumper trick?

Chuck(G)
May 22nd, 2010, 01:00 PM
finding this thread, i am going to ask, i have one of those 4869s and it refuses to work, i replaced the ALPS drive with a mitsumi one as the ALPS failed, but the mitsumi refuses to work on my 5160's or my 5150. I'd like to be able to slap a 720kb in this sucker and be able to use it with my 5150. Is this even possible? or do i need to do that little jumper trick?

You can either jumper your drive or swap a couple of conductors at the connector. I like to pry off the connector, pull off the wires that need swapping, then re-assemble the connector (it helps if you have an IDC crimper). It looks exactly like the original; the difference is that the wires now correspond to the 5150 ordering. You could also cut and splice the leads going to the connector. ISTR that it's only a couple of wires that need swapping to work for both drive/motor selects.

If you'd prefer, I can post the Diskettte Adapter/A pinout and you can compare it with the 5150 pinout shown above.

k2x4b524[
May 22nd, 2010, 01:46 PM
by jumpering the drive, you mean setting the drive select? Pardon my stupidness, but i had assumed that the external box did this for you, or does the drive jumper HAVE to be like DS1,2,3,4 or which ever?

wrljet
May 22nd, 2010, 02:13 PM
by jumpering the drive, you mean setting the drive select? Pardon my stupidness, but i had assumed that the external box did this for you, or does the drive jumper HAVE to be like DS1,2,3,4 or which ever?

The ALPS DFC222B05A drive in mine is not capable of being jumpered to work with the options provided natively. I had to add a wire for the MOTOR signal in addition to strapping DS0. (as shown in the pic I linked)

Chuck(G)
May 22nd, 2010, 03:05 PM
Okay, here's the DAA connector pinout:

1: NC 2: High Density 3-5: NC 6: Index 7: Reserved 8: Select C 9: Reserved 10: Motor enable C 11: Direction 12: Step 13: Head select 14:Write gate 15: Track 0 16: Write protect 17: Read data 18: Write data 19: Diskette changed 24: Drive C installed 20-23, 25-37: Ground

The important thing to notice is that the select on a 4869 is reversed--the drive C select and motor enable are where the drive D ones normally would be. It takes a little playing around--nothing major.

IBMMuseum
May 22nd, 2010, 06:44 PM
You should have mentioned that you were working with a 4869--I've got a bunch of them here and have done the pair swap at the drive connector many times--so much so, that I have a method for using packing tape and working only by pair color to do it and re-use the original connector.

I do recommend replacing the original 8272 with either an "A" part or one of the NEC 765AC parts (or any one of the equivalents from other vendors). The 8272 was a bit buggy in addition to having some timing issues and the original diskette adapter was the only one to use it. And I'd recommend just installing a 40-pin socket, so that if you ever wanted to go back to the original, it would be very easy.

Your recommendation to check the 4869 cabling is a good one, because the PS/2 adapters these units were designed to work with did truncate certain drive-select lines. A microchannel adapter with a FDC even had a somewhat-standard 34-pin connection that was only designed to run one internal drive. Without the stuff immediately at hand, I donīt remember what the drive has to be set.

EDIT: Whoops, just saw you addressed this...

k2x4b524[
May 22nd, 2010, 06:53 PM
as much as i know, this one befuddles me, which options are being set on the drive? And how does one set this up? *Non-techie explanation required*

Chuck(G)
May 22nd, 2010, 07:00 PM
If there's enough interest, I'll do a photo-essay on modifying the 4869 to work as a standard external drive.

k2x4b524[
May 22nd, 2010, 08:22 PM
You've got my interest in that one, my interest is at the FRONT of the line :)

IBMMuseum
May 22nd, 2010, 08:50 PM
If there's enough interest, I'll do a photo-essay on modifying the 4869 to work as a standard external drive.

FWIW, there is also the 720Kb version that would transfer over too...

wrljet
May 23rd, 2010, 04:53 AM
If you'd prefer, I can post the Diskettte Adapter/A pinout and you can compare it with the 5150 pinout shown above.

What is the Diskettte Adapter/A ?

Chuck(G)
May 23rd, 2010, 08:00 AM
What is the Diskettte Adapter/A ?

The Diskette Adapter/A (http://ps-2.kev009.com:8081/ohlandl/floppy/5_25-Floppy.html) was a PS/2 add-in card with one interal 2x17 internal connector and one DC37 external connector whose purpose was to provide support for 5.25" drives (both 360K and 1.2M) without making the user sacrifice either of his 3.5" internal drives. In other words, it was a secondary floppy controller for the PS/2 and most often bundled with the 4869.

The full-blown adapter(FRU 15F7996 and FRU 15F7996 ) were failrly uncommon; many users opted for the less-expensive pass-through (from the existing floppy controller) card (FRU 72X6758 ) and sacrificed the use of one 3.5" drive.

k2x4b524[
May 24th, 2010, 04:08 PM
Bump-Bumpity-Bump-Bump-Bump

Chuck(G)
May 24th, 2010, 04:21 PM
Bump-Bumpity-Bump-Bump-Bump

It might be more useful to say what you need.

k2x4b524[
May 25th, 2010, 07:44 PM
well ya true, but some times a good old fashioned, friendly thread bump doesn't hurt either.
I'm curious about how to convert the 4869 to work with the PC and the XT and would like a tutorial if at all possible

wrljet
May 25th, 2010, 07:45 PM
well ya true, but some times a good old fashioned, friendly thread bump doesn't hurt either.
I'm curious about how to convert the 4869 to work with the PC and the XT and would like a tutorial if at all possible

What the heck is a "thread bump"?

k2x4b524[
May 26th, 2010, 05:41 AM
In forums, if a thread has died for a while and no one has responded to it, or if it has fallen below the first page when you open the forum section, one used to go *Bump*. A simple message with the word Bump in it.

NsMn
May 26th, 2010, 05:48 AM
I'm curious about how to convert the 4869 to work with the PC and the XT and would like a tutorial if at all possible
The 4869 is MADE for these machines, if I'm not mistaken. All you need is the appropriate ISA card.

wrljet
May 26th, 2010, 05:54 AM
The 4869 is MADE for these machines, if I'm not mistaken. All you need is the appropriate ISA card.

The 4869 seems to be made for a PS/2. If you read the thread from the beginning you'll see how I did it,
and how Chuck prefers to do it.

Bill

IBMMuseum
May 26th, 2010, 06:29 AM
The 4869 seems to be made for a PS/2...

And to be clear, the 4869-001 is with a 360Kb drive, designed to connect to the PS/2 Model 30 and the microchannel systems using the pass-through adapter. The 4869-002 was a 1.2Mb version, and to be paired with the microchannel Diskette Adapter/A. I think the discussion so far has covered connectiong up a 4869-001 to a PC/XT.

Erik
May 26th, 2010, 06:41 AM
In forums, if a thread has died for a while and no one has responded to it, or if it has fallen below the first page when you open the forum section, one used to go *Bump*. A simple message with the word Bump in it.

Those are not a good idea here. If the content of a thread is worthy of attention and/or response it will get it. A bump, like all other content-free posts, will only get the ire of the moderating staff...

This has been a public service announcement.

k2x4b524[
May 26th, 2010, 03:03 PM
For clarification, i'd like to put a Chinon FZ-357, or an epson SMD-340 into the 4869, both are highly configurable, and i've got the card-edge adapter, but am still confused as how to make it work.

My 4869 is the -002 model
Not sure if i wanna mess with it, i'm still not sure of what i'm doing.

And Erik, sorry bout the bumping, but it's good to know your still around :)

Chuck(G)
May 26th, 2010, 04:22 PM
I'll get to it, but not before the weekend, sorry--got other things higher on the list.

IBMMuseum
May 26th, 2010, 07:32 PM
...My 4869 is the -002 model...

The case and cable are identical between the models, the only thing changed is the drive itself...

k2x4b524[
May 27th, 2010, 02:32 PM
Ahh, gotcha

ChuckG i look forward to reading it :)

Chuck(G)
May 31st, 2010, 11:09 PM
See my blog post (http://www.vintage-computer.com/vcforum/entry.php?87-Modifying-an-IBM-4869-external-floppy-box-to-work-with-a-5150)