EEVblog

Dave breaths life into the old Compaq Portable from 1984.
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[@adriansdigitalbasement]

Awesome! Yeah the 18khz/50hz signal you were seeing was the MDA scan-rate. The internal monitor on these is multi-scan and can run at either 15.6khz/60hz or the MDA rate of 18khz/50hz. Incidentally even though that scan converter says it can handle "CGA" it really means the 15.6khz scan rate... it's expecting an analog level input and no tthe TTL 5V signal that is coming from that card.

[@assadasdasdasdasable]

3:07

[@sneugler]

A completed repair on the EEVBlog? Impossible!

[@KinChungE]

16:43

[@Petertronic]

That GBS scan converter board is typically used in old arcade machines when changing them from CRT to flat screen. Used them a few times, with mixed results. It's cheap, but the more expensive ones give a much cleaner output!

[@Oldgamingfart]

Perhaps it needs to be in the case for all the grounds to tie-up? A 'chassis ground', so-to-speak..

[@stanburton6224]

I worked with the guy who designed this machine. Back in the day.

[@nazteeb]

My second work computer! Fantastic machine! :)

[@memadmax69]

From what I can remember, negative voltages are for the tape and/or disk drives?

[@tndabone]

The internal monitor is a different scan rate than the external 15K. The dip switches on the motherboard pick which kind of video card, not what video modes come out of the card.

[@frankowalker4662]

The composite issue looks like the same grounding problem I had a few months ago.

[@flymypg]

Nice launch and belly-flop, but I was expecting more explosions at the end.

[@rfmerrill]

Some older DRAM chips need +12 and -5 to work.

[@davidg4288]

You are a brave man to work on a Compaq portable. I remember working on those Compaqs back when they were still used and they were a nightmare compared to any desktop of the same era, as you have noticed. My "repairs" consisted of buying a replacement board and plugging it in, I never heard of anyone doing board level repair on those.

[@emmettturner9452]

I've had one of those GBS-8200 CGA2VGA converters back I'm 2016 for use with arcade boards. Since then, the video game community has turned it into a VERY competent scaler using custom firmware with some small tweaks/mods and an ESP8266 board to control it all via WiFi. The project is on GITHUB as "GBS-Control." I find it particularly useful since it properly handles 240p and consumer RGB (0.7v peak to peak, 75-ohm impedence) when it is very difficult to do anything with 240p RGB in NTSC land. :)

[@dianeattaway8733]

TO-3, now that's a device I haven't seen in a long time

[@leroycasterline1122]

Ah, the Compaq Portable - that was one fine (if heavy) machine. Portable computing and a nice workout in one package.

[@frankgrudge8823]

Love the repair vids Dave!

[@johnsonlam]

Nice to see it's working.

[@mdbssn]

IC hook clips are great for these kind of power header connections when compared to alligator clips! Definitely my preference, usually easier to keep away from other pins and more secure.