[cctalk] Re: 5155 lugable

A further, [probably unneeded] clarification, One slot is different. The othersare all alike, BUT the 5155 had stuff in the way (unlike the similar Compaq) that forced placing boards according to length. Some boards won't work in the different slot. To discourage people from putting other boards in that slot, IBM provided a "FREE!" Asynch (RS232, current loop) board, already installed in that slot, so that the user would not even have to install it. Apparently, due to the immediate third party market of multi-function cards when the PC came out, IBM sold much fewer ot the asynch cards than they had expected, making giving away a "FREE!" card in the different slot economical. The IBM FDC board was hard wired for 5.25" MFM. The changes needed for others were not extremely major (Flagstaff Engineering, at one point had an IBM FDC board, with lots of colored wires, to do 8" SSSD.) There existed numerous after-market FDC boards with capabilities of FM, MFM, and other data transfer rates. The best known of those was the Micro Solutions ("Uniform") "Compaticard". But, there were even generic ones. And, of course, additional software was needed to handle anything other than the PC-DOS/MS-DOS 5.25" MFM with IBM/WD traack and sector structure.. -- Grumpy Ol' Fred cisin(a)xenosoft.com XenoSoft http://www.xenosoft.com On Fri, 29 Aug 2025, Bill Gunshannon via cctalk wrote: > > > On 8/28/2025 3:03 PM, Tony Duell wrote: >> On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon via cctalk >> <cctalk(a)classiccmp.org> wrote: >>> >>> >>> >>> On 8/28/2025 1:07 PM, Tony Duell wrote: >>>> On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon via cctalk >>>> <cctalk(a)classiccmp.org> 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. > >> >> 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 > 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 ) > Slot 4: HD Controller (WDX-GEN) > Slot 5: Video-Serial-Paralel > Slot 6: Empty > Slot 7: Empty > Slot 8: Empty > > Recommended ordering? > >> >> >>> >>>> >>>> Note that if you want to remove or open up the monitor and PSU you >>>> need Bristol Spline tools. >>> >>> Does it make me a true geek if I say that I actually have a set of them? >>> >>>> And tamperprrof Torx for the PSU cover. I >>>> had to take the latter apart, the mains input filter capaciitors were >>>> being antisocial and breaking down. I replaced them before they filled >>>> the worshop with magic smoke >>> >>> PSU seems fine. >>> >>>> >>> >>>> And how does the POST die? What error code, etc. >>> >>> Well, lets confuse things even more. Took th3e card out again and >>> the system tested all 640K and went into BASIC. >> >> Which is what you'd expect with no bootable disk in the system. >> >> >>>> What is the make and model of the hard drive itself? >>> >>> 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. > >> >> 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. > >> >> 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. :-) > >> >> Finally there's the Hardware Maintenance and Service manual for the >> portablePC. This is a 'boardswaper guide' but it tells you what to >> unplug and what to unscrew to get things out. > > > I guess next is to spray all the edge connectors and slots with DeOxit > and out it all back together. > > bill >