#osi challenger 4p

[commodorez]

FOUND ANOTHER FUCKING SOLDER BRIDGE

See those areas marked in red? Those were holding back my OSI 540B replica video board from generating video. This board is of a design where solder mask was not always a given so it's very easy to bridge traces. I found one last spring (left), and I found another one this morning thru tracing the weirdness of the video signal, until I noticed that a pair of 74LS174's weren't passing any signals.

Turns out they were locked up, because master reset was pulled low by another solder bridge (right). See that middle line marked Q3? That should be similar to D3, but it wasn't.

I wasn't sure I had fixed it, until I started tweaking analog video levels again, and suddenly I had something visible on the screen! A few keystrokes later and... BASIC!

FUCK YEAH, BASIC!

And so I decided to run my usual SIN COS test:

The video signal is a bit low voltage, so it appears kinda dark. I need to tweak alot of the analog parts of the circuit, possibly modify a few things to get it playing nice. I also need to run test programs for the color video modes, the whole point of doing this replica build. Here's an original 540B built for monochrome video:

And here's one built for color video:

I built this thing in summer of 2020, it's nice to see it finally video-ing.

FUCK YEAH, I needed that win. I really did.

#osi #ohio scientific #osi challenger 4p #challenger 4p #osi c4p #analog video #composite video

[commodorez]

OSI Challenger 4P iboards

#osi #ohio scientific #osi c4p #challenger 4p

[commodorez]

Ohio Scientific Challenger 4P

#osi c4p #ohio scientific #challenger 4p #basic #amber monochrome

[commodorez]

OSI C4P on an RCA monochrome monitor

#osi #osi c4p #ohio scientific #challenger 4p #rca

[commodorez]

New extended surface for my workbench.

#workbench #osi challenger 4p #heathkit h89 #altair 680 replica #hakko 472d #weller wesd51

[commodorez]

Ohio Scientific Challenger 4P

A keyboard, a 502 CPU board featuring a Synertek manufactured 6502, a 540A graphics board, a linear power supply in need of a capacitor replacement, and some sketchy wiring all crammed into a beautiful wood and metal case.

1978? 8K of RAM? One of the finest and fastest BASIC versions available at the time? Oh yes, this will be fun.

#osi challenger 4p #Ohio Scientific #osi 502 #osi 540 #challenger 4p #6502 #osi basic #this machine is related to the cactus in some ways

[commodorez]

Ohio Scientific Challenger 4P

#ohio scientific #challenger 4p #osi c4p #osi

[commodorez]

Look at 'em go!

#cactus #6502 homebrew #osi c4p #ohio scientific #h89 #6502 #blinkenlights #challenger 4p

[commodorez]

Ohio Scientific Instruments Challenger 4P rewire

#osi #c4p #challenger 4p #ohio scientific #osi c4p #6502

[commodorez]

The Cactus at VCF East XIV

From left to right: OSI Challenger 4P Toshiba Libretto 70CT Cactus ADM-3A terminal (loaned by TangentDelta) November ‘77 of Byte Magazine featuring the Kompuutar Mini OSI-300 kit CGRS Microtech 6502 front panel (loaned by Bill Degnan) OSI-300 (loaned by Bill Sudbrink). 

Not pictured, but absolutely vital to the success of this year’s exhibit, @aperture-in-the-multiverse

#cactus #VCF East XIV #Vintage Computer Festival East XIV #VCF East #VCFEXIV #CommodoreZ goes to VCFEXIV #6502 homebrew #retrotech #osi 300 #cgrs microtech #adm3a #ohio scientific #toshiba libretto #libretto 70ct #osi c4p #challenger 4p #please do not water the cactus

[commodorez]

Turns out that if you remove enough of the crap RAM and press the shift lock, you can get it to boot into BASIC. 

#osi challenger #osi c4p #challenger 4p #6502 #ohio scientific

[commodorez]

#challenger 4p #osi c4p #ohio scientific #6502 #mos 6502

[commodorez]

8K and BASIC?  Yeah, I can work with that.

#Ohio scientific #osi c4p #challenger 4p #6502 #BASIC

[commodorez]

Overhauling the keyboard of my Ohio Scientific Challenger 4P.  That wasn’t as tough as I anticipated it to be.

#6502 #ohio scientific #osi c4p #challenger 4p

[commodorez]

Coming up next on OSI Challenger 4P issues, “Why the hell is this machine not resetting?”

Turns out I can’t trust all of my fancy new RAM. 

#6502 #osi c4p #challenger 4p #ohio scientific