In no particular order.
Yesterday I was able to restore enough of this early 486 #motherboard to get it booting.
Someone removed the BIOS chip (I used a dump off a similar mobo), a few logic ICs and the oscillator (I put a 40Mhz one in there, even though I suspect this results in an overclock).
Still no idea of what kind of #cpu is installed, an #486SX probably... The heatsink is glued. #retrocomputing
Couldn't leave the #Amiga closed up for long... Even if not documented anywhere I could find, you CAN get a rev.3 main board to use the trapdoor slot as chipmem (thus going to 1mb). It's slightly harder than a rev.5 as there are no jumpers, but basically the same procedure:
- cut the EXRAM trace going to the trapdoor
- replace the 8371 agnus with an 8372
- make sure agnus pin 41 is not tied to GND
- pin 59 of agnus must connect to A19 and not A23
I added a jumper to every cut
The Franken #amiga 500 rev.3 I found at the fleamarket is not in a bad shape: all the diagnostics I threw at it passed. I took the time to replace a few crusty sockets, add my #eprom adapter and cut a few traces/add jumper wires to ease future expansions. Pity the rev.3 is not as easy as other models to expand to 1mb of chipmem.
The keyboard is not in good shape though, most of the keys don't register all the presses, if at all. Will have to clean it.
Testing the #Philips green #phosphor #monitor I found. Surprisingly not only it works, but it has no burnin...
Great in text mode, not so much in color mode, still, not bad at all.
I might have to try the DIN connector on the back, as it mixes the colours directly inside the monitor, which I suspect is going to be better than feeding it NTSC composite, that is probably just confusing the circuitry. #retrocomputing #fleamarket
Preliminary dump of the voice data from a McDonnell-Douglas H05A0035-10 Central Aural Warning System. I believe first flown on the DC-9.
Voice data was stored on three 256Kx8 EPROMs. I traced out a schematic of the voice board and dumped them in-circuit, so there was no need to try and desolder the chips from the heavily conformal coated multilayer board.
For precision's sake, the games shown above do not put more than 16 colors on screen at the same time, but they do allow to use the full 64 color EGA palette to set the 16 colors used onscreen. Thus, graphics is no longer tied to the original CGA palette.
It is not well known that you can get 320x200 at 64 colors with #EGA by using a compatible monitor or an TTL-to-RGB adapter (and a compatible game). Here I am using my EGA-to-RGBs adapter based on an EEPROM with a standard TV (SCART connection): https://github.com/hkzlab/EGA-2-RGBS
I'm working on an improved version using a GAL16V8, but this is already pretty good.
Built & tested rev 1.2 of my #ES1868F sound card. I added an header for the AUX input and also SMD ferrites on input and output ports, as recommended by the #ES1869 datasheet (BTW, I have a design for that one too in queue).
As usual, you can find everything here: https://github.com/hkzlab/ES1868_ISA8
My usual luck: I decided to buy an #extron converter to try various computer swith my TV.
Arrives, works for 15 minutes and then dies.
Inside I see various caps leaking in the PSU section. Replaced. The PSU outputs its voltages just fine, but still no outward sign of life. And no service manual available... And half of the main ICs on there have their top abraded.
Fuck me for having bought this...
Life has caught up with me in one of the worst ways possible, so I couldn't dedicate as much time as I wanted in testing my #ES688F / #OPL3 #ISA #soundcard .
I'll get around to it someday, but it's pointless to delay the release.
I dedicate this to my cat Pezza who is very ill, and who has accompanied me since the beginning of the lockdown and my adventure into a new phase of my life.
In no particular order.
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