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Macintosh Portable 34 pin to 50 pin SCSI cable

martona

Active member
Thanks!

Yes, I saw the crosstalk mention above, but... but.. the photo... :)

To be perfectly honest I was concerned about not finding the right wire when I get to the 34-pin connector if I twist odd & even pairs together. That's why I cut the gordian knot, so to speak.

Of course I could have just used a sharpie before twisting the pairs. But such a "complicated" solution did not occur to me when I started, and It's too late now, I only need to do the DP wires and add the Molex connector.

I do have material for another cable, so I might make a proper one if this one works. (If it doesn't, I'll HAVE to make another one.)

 

martona

Active member
Well, the cable is finished. It's not pretty, but it's mine. :)

Now I'm off to hook it up. Hopefully there will be no smoke.

xg9ix.jpg.d577d0714ebf9a988d6c12dcd61b4ba0.jpg


 

Trash80toHP_Mini

NIGHT STALKER
Easy trick.:

01) leave an extra couple of inches of ribbon sticking out the off end side of the 50 pin IDConnector

02) split all the wires on that side, lopping off the signal lines

03) the remaining lines will all be connected to the ground side of the cable, strip the ends

04) bundle them together and attach the alligator clip lead of a $.99 Continuity tester to the bundle

05) leave about an extra inch of length on the business end of the ribbon cable

06) mark across the entire width of the cable at the IDC point with a sharpie.

07) split all your pairs from the beginning to end

08) split that one inch extra on each twisted pair

09) apply continuity tester to see which of the pair doesn't light up

10) nip off the side that does light up about 1.5" short of the sharpie line with your dikes

11) strip the ground line waste off the signal line back to the nip

12) punch your signal lines down on the IDC connector's forks right at the sharpie line (for equal length signal correctness)

Did I mention using a Vise to do the final punchdown of the IDC tops?

 

martona

Active member
Thanks Trash80, that's actually pretty cool!

I may have to do another cable in which case I'll follow the above steps.

There was no smoke, but despite the below photos, it's not a complete success either.

jCOxX.jpg.9ba3e4200857b893578139c923467e38.jpg


zPcbe.jpg.23b89145d616ac0ea4ac90bb7919872f.jpg


I had to make one modification to the diagram: TERMPWR should be disconnected. All 5V pins from the 34-connector side go to the molex red wire. The TERMPWR line on the 50-pin side is cut. This way I got the Portable to recognize the disks. (In my photo above TERMPWR is still connected to a 5V pin, I had to change this to breathe life into the system but forgot to snap a new pic.) FWIW mcdermd's photo has TERMPWR disconnected too.

But I still have one problem. There may be something wrong with the cable I made, or the harddisks, or possibly the diagram, but here's the behavior I'm seeing:

- With the original 34-pin HD installed, the Portable powers on and boots fine.

- With the AztecMonster, the Portable powers on and after some deliberation it flashes the dreaded disk with a questionmark. At this point if I press the reset button on the machine it boots fine. (As per the photo above.) This isn't some one-off instability issue; out of 20 cold starts all of them went the same way. Have to wait for the flashing questionmark, then press reset to get it to recognize the HD.

- I tried it with a regular 50-pin Apple/IBM SCSI HD (it came from my Color Classic) and I get the same behavior: power on -> questionmark -> reset -> boot, so this isn't the AztecMonster's problem.

Any thoughts? Just for kicks I disconnected the RST wire temporarily, and that resulted in a no-boot scenario; the reset button stopped having an effect. Reconnecting RST reverted to the behavior described above.

I'm at a loss.

 

martona

Active member
Well, this is interesting.

I made another cable so I don't have to keep pressing Reset to boot my computer.

This guy posted wiring instructions too:

http://web.archive.org/web/20080705022723/http://www.antinode.org/mac/port_scsi.html

They're very much in line with Trash80's diagram, except he reached the same conclusion I did: TPWR should be disconnected.

Anyway, I followed the advice above re. twisting the ground wires, etc. Double and triple-checked every connection. The new cable turned out stunning. I hooked it up, and.... flashing questionmark.

Press Reset: smiling Mac, boot, no problem.

I found a workaround though: Setting the HD's ID to ANYTHING above 0 cures the problem. I currently have it on 1, and it cold-boots just fine. Leaving it at zero requires me to press Reset.

Totally unscientific speculation: Is it at all possible that the Portable starts probing the SCSI bus way too early, and the HD is not yet read when the probe is at zero? But a few milliseconds later, the HD can be found at ID 1? Did anyone here have issues running a Portable internal HD on ID 0?

In any case, thanks everyone for your help with the cable!

-Marton

 

Trash80toHP_Mini

NIGHT STALKER
Thanks for confirming that I was mostly right, I'm no expert. Maybe I can find something in the Portable Docs about that termination power quirk.

Got a pic of the new cable to share?

 

martona

Active member
Sorry, no pic, other than this:

CULbI.jpg.1695403e598874c98f872919429adcf4.jpg


I'd have to take off the keyboard cover to unplug the other end for a photo, and the computer is old & brittle plastic and I'd rather keep the wear and tear to a minimum.

I'll need to circle back and finish the molex cable to ribbon cable connections properly; I didn't have heatshrink tubing on hand so they're just covered with electrician's tape for the moment. When I do that I'll snap a pic of the whole thing and upload it here.

Any thoughts on not booting with SCSI ID 0?

 

Trash80toHP_Mini

NIGHT STALKER
Any boot'll do you. Not a clue why it works out that way, but it works, so it works for me!

Nice job, looks like you split and twisted each pair as well. get some tiny zip ties to replace the tape when you get the shrink wrap and you'll have it lookin' like a pro did it! [;)] ]'>

 

martona

Active member
Unfortunately it will never look too professional; I don't know if you noticed the silicon sealant around the AztecMonster. I needed something to hold it in place (the HD mounting screws did not fit) so i basically glued it in place. It's very sturdy and provides a secure (and what's just as important, undoable) hold but it doesn't look awesome. On the plus side, the machine is completely silent.

I will probably need to downgrade the OS to 7.1 though; 7.5.5 runs unbearably slowly, even with 7 megs of RAM.

 

haplain

Well-known member
I was wondering if anyone were would be interested in construing a few of these cables for me? Either PM me or post here. I'm looking for 2-10 depending on where pricing falls. Thanks

 

uniserver

Well-known member
here is my first attempt, i decided to use a 100mb scsi internal zip drive

it spins up but does not boot. i need to make another one i think, the cable needs to be made longer!!!!

the visual schematic confuses the heck outta me. why is the rear external connector in the diagram?

less is more.

IMG_1975.jpg

Trash one of these days, can you make a updated graphic computerized make the necessary changes?

Then maybe ask for donations? I would donate, if its easy to follow and allows me to be successful, sure!

I know you are great at that sketch up... or what ever app that is you use....

 

uniserver

Well-known member
yes,

The wife and I are going to sit down and come up with a method of production.

Now that we have one working, and know exactly what to do to make it work.

This first one is going to hap. he's in desperate need.

 

Trash80toHP_Mini

NIGHT STALKER
1) Get two pieces of wood the appropriate lengths . . .

. . . with enough extra to clamp it to the work surface if you can still get the connector on the clamp end into your vise.

2) Epoxy headers and a MOLEX receptacle in the perfect positions on one board.

3) Make a slitting diagram on the second piece of wood with enough room to staple or clamp the ends of your ribbon cable at the ends.

4) Make slots in a piece of cardboard to mark the cable appropriately, with holes to register it over pins in the slitting board

Then do your wire slitting at one workstation . . .

. . . mount your IDCF connectors on the headers on the other workstation . . .

. . . do your cable fabrication/temporary punchdown & soldering . . .

. . . remove the fab jig . . .

. . . do your final punchdown on the vise . . .

Bonus points for setting up the boards/jigs at comfortable angles on a larger assembly jig the width of your table with the vise bolted to one side that hangs off the end of the table for bolt clearance. If you don't want to/can't clamp the production station board to the table, just make it enough larger to use 1x2 stock to make a rim/frame to fit around the table and pile a couple of cinder blocks on top during production . . .

Dunno . . . just off the top of my head . . .

 

uniserver

Well-known member
revision #4

IMG_2022_thumb.jpg

Also, with this 72gb u320 2.5" drive project i have been working on.

Managed to pull the 700mb Quantum out of my PM 6100 and install the new kind.

anyways looking at the original 40mb Conner HD it says +12 250ma / +5 275ma

Well this 700mb drive from the PM 6100 says +12 210ma / +5 200ma

So I would assume this newer more energy friendly drive would be a good choice.

IMG_2023_thumb.jpg

takes the wife 20 min to color code

takes me about 1:20 to solder all the wires on

Also this thread I installed a SCSI Internal ZIP 100mb, seems to work out good.

viewtopic.php?f=10&t=21236

 

Trash80toHP_Mini

NIGHT STALKER
I didn't realize you were cutting and splicing every wire until I saw the color coding piccie. Why did you decide to splice the connections rather than rearranging the uncut wires on the IDC34F side?

 

uniserver

Well-known member
because hap is going to sell these on ebay, and I need the IDC's to be solid, those idc are mechanically designed to be crimped to a cable not cut wires.

I don't want some big monkey fingers ripping out the wires after the first day.

 
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