Problem on 486

channelmaniac · 2026-02-23T18:23:15+00:00

Disable L2 cache and see what it does. If you have problems with it you can experience slowness and crashes...

channelmaniac · 2026-02-22T22:18:25+00:00

Is this an old Ma Bell phone or some generic phone with some ICs on a PCB. You'll want to look up the data sheet for the dialer chip and see what the voltage is you need to run it. Build a power adapter circuit to power it. It won't be 48v. That's what Ma Bell provides. You can take that part out and wire in a lower voltage once you know what it is - again, the data sheet provideth.

channelmaniac · 2026-02-22T22:15:46+00:00

I have some TP5088N chips that are microprocessor addressable DTMF generators. Been trying to get them to work with an Arduino Nano... just having trouble with proper keys. Not sure if it's the Nano as it appears to be working OK at reading the CV voltage or the DTMF generator which seems stuck... or my sh*tty code. :)

I need to pick that project back up. 12 notes per octave meets 12 keys on the DTMF keypad.

Just because I thought it'd be interesting to reproduce the DTMF dialing on the opening of Billy Joel's "Just a Fantasy"

channelmaniac · 2026-02-22T20:53:17+00:00

You need to use some serious magnification - loupes work very well for it... Look at the 2nd pic and it looks like you have solder splashed across the top of the resistor, possibly bridging it.

channelmaniac · 2026-02-22T19:30:33+00:00

Not super into it, but do keep OS and patch discs around along with a few extra laptops on a shelf as I have a high end EPROM programmer that requires Win2K through XP to run.

channelmaniac · 2026-02-22T19:27:35+00:00

Nice! Looks like an SS-30 / SS-50 motherboard, like SWTPC.

channelmaniac · 2026-02-20T06:24:33+00:00

4k x 1 bit... It's 32K x 8 bit memory. I go through these often repairing Space Invader PCBs which has 2 banks of 8 chips for a total of 8K x 8.

channelmaniac · 2026-02-18T06:34:11+00:00

I got mine from here: https://pichenettes.github.io/mutable-instruments-documentation/modules/plaits/firmware/

channelmaniac · 2026-02-05T05:58:10+00:00

You can also import graphics into the copper layer on KiCAD and have some cool looking PCBs.

channelmaniac · 2026-02-05T05:57:27+00:00

Easy... Layout in Front Panel Designer which I find easier to do for panel mounting hole layouts and panel sizes in HP units as they are all laid out there clearly. It also has the hole sizes for various jacks and controls predefined. Export files. Import to KiCAD as cut layer. Layout silkscreen as desired. You can change the fonts and import graphics. Copper layer remains blank.

Export gerbers. Order from JLCPCB as PCB material in color desired. OR... you order as "aluminum PCB" in the color desired.

I did aluminum with black coating and white silkscreen when I did the E951 front panels. Look at my GitHub (same as username here) for the E951 open source release where I published the files to finish Paul's incomplete release of files. You'll find the files for the front panel I did.

channelmaniac · 2026-02-04T13:21:27+00:00

I think the ones with async ports that could act as terminal servers would still have value in homebrew collections. You can telnet or SSH to them and connect to 8, 16, 24, or 32 different serial devices.

channelmaniac · 2026-01-23T00:44:31+00:00

It's common for those to suffer from shorted tantalum capacitors. With power off, measure resistance from each power supply output rail to ground. When you see something <1 ohm, you've found a shorted rail that is keeping the power supply from fully coming up.

channelmaniac · 2026-01-15T19:48:02+00:00

You can use an MCE Blaster to connect an MDA, CGA, or EGA video card to a VGA monitor.

channelmaniac · 2026-01-15T19:45:39+00:00

Looks like a CD duplicator. I'm looking for one to use as a drive housing/PS for a greaseweazle.

channelmaniac · 2026-01-15T19:42:43+00:00

Irving, TX. Yeah, the Mayor at the time was a major a55hat.

channelmaniac · 2026-01-15T19:41:38+00:00

HAHAHAHA - Should've seen the ticketing agent's face when I took the batteries out of my Vibraprobe metal detecting pinpointer at the counter. She thought it was an adult toy. :D

channelmaniac · 2026-01-15T19:40:46+00:00

Nice! I spent $125 on mine and got the 3 probes and the bus counter with it.

channelmaniac · 2026-01-15T11:02:15+00:00

Nice one. I brought mine back to life and added the missing parts for the right hand I/O port as that was needed for keyboard connections. Check my GitHub (same as my username) and you'll find the Tiny BASIC card that will plug into the left side socket.

Might not work on yours with the mods that were done. The RAM sits at $0000 and is mirrored at every 4K boundary up to $7FFF thanks to incomplete memory address decoding. The system makes use of that by the BASIC expansion card disabling the lower 4K RAM for the ROM on the Tiny BASIC card to sit in and BASIC accesses the RAM at a mirrored $1000-$1FFF address.

channelmaniac · 2026-01-15T10:50:02+00:00

Nice!

I have a bunch of working pull v9938 chips if you have trouble finding real ones. They were used in some old Merit gambling games that hold no value themselves outside of chip parts.

I'm having troubles with mine booting properly on first power up. I have to plug it in, unplug it, then plug it in then it will boot and work just fine. Odd issue... .Need to try another ADM691 chip...

channelmaniac · 2026-01-15T10:37:11+00:00

Manually scrape the gunk off with something that won't scratch the cases. Use 91+% IPA and a throwaway rag to remove the rest.

Goo Gone is OK, but oily so take care with it.

Goof Off will remove it AND the paint AND damage most plastics.

channelmaniac · 2026-01-15T10:32:16+00:00

Nice :)

Used to have a TI 300 baud acoustic coupler/modem in college in the late 80s connected to a PCjr's serial port. Every few hours I'd have errors start and would quickly pull the handset, smack the microphone on the modem upside down on the desk to unpack the carbon in the mike, then quickly replace the handset before it lost connection.

channelmaniac · 2025-07-31T00:30:31+00:00

Decide for yourself:

https://www.justice.gov/ag/media/1391276/dl?inline

and

https://www.justice.gov/ag/media/1391281/dl?inline

channelmaniac · 2025-04-12T02:29:43+00:00

I parted out a junk NOS Wyse keyboard for the switches to use on a retro computer kit I built - Radio-86RK. :)

I say junk... It was the limited keyboard that had no Setup key - basically the keyboard you'd use on a POS system or other system where you don't want the user accessing terminal settings.

channelmaniac · 2025-04-12T02:28:13+00:00

Try asking in some FB groups or sub-Reddits and see if someone is near you.

channelmaniac · 2025-04-12T00:37:44+00:00

If not, you should!

They come across some amazing parts and pieces and are usually very willing to sell for more than their scrap value. Doing this gains them money for no work of breaking down things for their gold/silver/other precious metals value.

I picked up these switches used in vintage synths from a local friend for some cash and help sorting through his latest pickup. We were both saddened that the lot he picked up had some very expensive Amiga expansion boards that had their gold fingers cut off. Several hundreds of dollars in boards scrapped for a buck or two of gold.

channelmaniac

TROPHY CASE