On Fri, Aug 29, 2025 at 2:26 PM Bill Gunshannon via cctalk <[email protected]> wrote: > > > > On 8/28/2025 3:03 PM, Tony Duell wrote: > > On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon via cctalk > > <[email protected]> wrote: > >> > >> > >> > >> On 8/28/2025 1:07 PM, Tony Duell wrote: > >>> On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon via cctalk > >>> <[email protected]> wrote: > >>>> > >>>> > >>>> I finally got the missing keyboard and now it is time to try > >>>> and revive it. > >>> > >>> I restored one some months back. Mine is 100% IBM boards and options.... > >>> > >>> The portablePC has a normal XT motherboard in it. The standard video > >>> board is the CGA one, with the composite output (on the 4 pin > >>> connector originally designed for an RF modulator) feeding the > >>> internal amber moniitor. This is actually a Zenith unit. > >> > >> That explains the weird little cable stretching over some of the boards > >> and getting in the way. :-) > > > > It's normally yellow and black twisted pair. > > Interesting. Not coax.
Not in the origiinal IBM version. > > > > > As standard, the CGA card goes in slot 1, closest to the PSU. Floppy > > controller in slot 3. This leaves slot 2 as an empty full-length slot > > and slots 4-7 as half-length ones. Slot 8 is not really useable. Being > > an XT motherboard, the card there has to assert the buffer enable pin > > on reads. The only IBM card that will do that is the async serial one. > > And it's about 1/4" too long to fit, it fouls the power connectors on > > the drives. > > More interesting info. I was not aware of there being any priorities > on the IBM PC bus. I thought all the slots were the same. At least Apart from slot 8 in an IBM PC/XT motherboard (which this is), all slots are the same. The ordering I gave is simply how the machine was shipped from IBM, it makes sense as it gives the neatest run of video and floppy cables. FWIW, my 5155 has the following cards : 1 CGA video 2 Data Acquisition/Control 3 Floppy controller 4 and 5 Async serial (modified so you can use either RS232 or current loop without opening the case) 6 and 7 Parallel printer (modified to have bidirectional data lines) I've also done the motherboard mod to have 640k RAM there > in the past when I last worked with PC's at the hardware level (a > really long time ago when they were new) I never saw any needed > ordering of the cards. > > Here's mine, satrtng from the PSU: > Slot 1: That CIL thing (now that I have booted without it I think > it was an interface to some weird lab device, > They had similar interfaces in their Apple ]['s > as well.) > Slot 2: Memory > Slot 3: Floppy ( a long card ) That may be the original IBM card > Slot 4: HD Controller (WDX-GEN) > Slot 5: Video-Serial-Paralel Cerrtainly not IBM! > Slot 6: Empty > Slot 7: Empty > Slot 8: Empty > > Recommended ordering? Whatever fits in the case and lets the cables run neatly. > > >> No idea yet as it is buried in the system below the floppy. But I > >> plan on pulling it out as soon as I figure out the mounting scheme > >> for the disks. > > OK. I took it all apart. Miniscribe disk. With it out I hooked it > up to an ext5ra PSU I had and toggled the power on and off a bunch > of times. It finally spun up and the blinky LED is not longer blinky. It may work for the moment. I'd grab any interesting data off it ASAP though. > > > > > I seem to remember you need a 5.5mm or 7/32" spanner and nutdriver to > > do that. You take off the earthing bracket on the right hand side of > > the drives towards the rear, then loose the other 3 screws on each > > drive and slide them out backwards. > > Ended out having to take the screws all the way out so I could > wiggle them a lot. Very snug fit, especially the fascia. If the floppy drive is the orginal Qumetrak then there are little plastic spacers on the screws to fit into the recesses on the drive chassis casting. One of mine was missing so I milled a replacement from plastic block > > > > > There are some useful manuals on bitsavers. The Technical Reference > > for the PC/XT and portablePC gives the motherboard schematic and BIOS > > source. The Options and Adapters volume 1 gives the schemaitcs for the > > drives and monitor. And volume 2 gives the CGA and floppy controller > > schematics (and lots of others). > > Pfft. Who needs manuals when you have google and youTube. :-) Well I do. To the extent that I bought all the Techrefs from IBM many years ago and have a shelf of them upstairs. I've also downloaded the bitsavers ones of course. Along with manuals for literally hundreds of other machines. Maybe you can find a failed component on your own but I am stupid enough to need the schematics. I have never been able to learn how to do anything from a video, for me it's the most ridiculous way to present such information. And there's so much misinformation on the web (in all fields) that I prefer to start from the original manuals rather than somebody's version of whatever -tony
