On Fri, Aug 29, 2025 at 3:51 PM Bill Gunshannon via cctalk <[email protected]> wrote: [Video cable] > >>> It's normally yellow and black twisted pair. > >> > >> Interesting. Not coax. > > > > Not in the origiinal IBM version. > > Just a comment that I found it interesting. Surprised there > isn't a lot of noise on the screen.
In the original it's quite short. And of course it's a low-impedance connection, terminated with 75 ohms at the monitor end. The main 'noise' on the screen is due to the chroma subcarrier which does appear on solid regions. > > 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 > > It's TEAC 55. Only one of those spacers was there. Another part of your machine that's been swapped out at some point. > > >> > >>> > >>> 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 > > Sorry, I was just trying to be humorous. I have piles of paper manuals > for most of my computers. Unfortunately I've seen the results of people following ill-informed instructions on the web, particularly with audio amplifiers, etc. The results sometimes end up on my bench and I have a lot more work to do than if I simply had to find the original fault. > As for failed components, I have never and > would never waste time trying that on a PC class machine. I do, particularly on a machine that's not just another random clone, for example a genuine IBM one. It's as historic as any other classic computer. And I am much more likely to have the right IC in stock than the right replacement board. > Now, on a > PDP or VAX.... Still have an oscilloscope. Just one 'scope? -tony
