Retro-Repair Adventures, Part 2

Shawn Delahunty's picture

Retro-Repair Adventures:

  • Part One
  • Part Two (You're here already. Quit clicking.)
  • Part Three
  • Part Four - (coming somewhat less soon)

Diagnosing the Obvious... Problem #1 - Faulty Power Switch

The initial problem I encountered with my VIC-20 flummoxed me---I found myself unable to even turn the dumb thing ON. The main power rocker-switch on my VIC was unhhelpfully frozen in the O-F-F position. Initially, I suspected that a piece of internal plastic had cracked with age, jamming the switch. But as I fiddled with it, I had one of those odd moments of photographic memory recall---I could clearly remember having to fight with the switch in my later teen-aged years. I also recalled that it grew much easier to flick the switch once the VIC had been on for a while and heated itself nicely.

Cranky old switchCranky old switch So I tried forcing the thing. Nothing, except for a sore thumb.

Ok, fine. Time to up the voltage--I started prying on the switch with the handle of a screwdriver. Nothing. All right, maybe just a little MORE force...

** CRUNCH! **

I cringed at that horrible sound, but the switch did move freely now. I plugged in the VIC, flipped the switch to ON, the red power LED flicked to life, and the TV... well it displayed something which almost, but not quite, resembled an image.


Diagnosing the Obvious... Problem #2: Heinous Video Output

I took a close look at the screen:

Looks like crap, must be crap.: Kinda melty, kinda smeary, kinda hard to read.Looks like crap, must be crap.: Kinda melty, kinda smeary, kinda hard to read.

"GAAAH! My Eyes!
Bloody stupid RF modulator.... (*grumble*grumble*)... Rassin' frassin' argle-bargle schklemfurken..."

This was TERRIBLE. What was causing such a horrible video signal? Had my VIC just somehow gone totally faulty with age?

Sadly, no. Nothing was broken. It looked like that ON PURPOSE. (As it turns out, there was another visual problem, not related to the video circuitry inside the RF modulator. But we'll get to that further below.)

Yuck. I'd honestly forgotten just how HORRIFIC the image quality of my VIC-20 could be... one of those rose-colored nostalgia things I suppose. Either that, or perhaps laser-corrected 20/20+ eyesight and 13+ years of crisp LCD screens have made me a wee bit pickier.

Now it's entirely possible that, as a kid, I simply didn't realize just how BAD the thing looked. Abysmal eyesight plagued me back then. My super-hero name would've been, "Captain Coke-Bottles", or "Telescopic Goggles Guy", or more accurately, "Dear-GOD-don't-glance-at-the-Sun-or-you'll-melt-your-brain Dude".

NASA could've saved a bundle on the Hubble Telescope optics repair mission by just sending up a roll of duct-tape and my old eyeglasses. Squandering my youth, endlessly staring at the distorted display on my tiny 13-inch black and white TV probably didn't help things much either...

No matter what the case though, this poor video output quality wasn't something peculiar to the VIC-20. The C-64, Atari 2600, Atari 400, and most other systems, all suffered the same problem. Virtually all computers and game-consoles of the 8-bit (and early 16-bit) era, output their video signal in what is known as 'composite-video'. Since specialized monitors with composite-input capability were an impossibly laughable luxury for most families, and since most TV's of that period didn't have any such thing, computer and game-systems came with an 'RF-modulator' box: The Source (of the crap): Anyone want an RF modulator?The Source (of the crap): Anyone want an RF modulator?

This box contained circuitry to convert the computer's native composite-video signal into 'something' which you could pump into your TV's antenna feed. Net Result? It "kinda, sorta, mostly worked." But you got a lot of "Visual Artifacts" as a result of all this double-reverse-Secret-Squirrel signal-conversion nonsense. 75% of the time it looked TERRIBLE; just absolutely heinous, washed-out, off-color muck. About 20% of the time, you got a decent picture, and would carefully avoid bumping cables or connections. The remaining 5% of the time it was utterly unviewable, so you'd start wiggling cables and whacking the side of the TV to get it to settle down.

(What I describe here was typical on machines using the NTSC video standard. Europe's PAL and SECAM standards ostensibly provided better signal quality, at the cost of reduced frame-sync/framerates. I find this dubious, and suspect they sucked equally. But I can't personally verify that, as I never saw those output formats.)

Interesting Historical Note:
A peculiar psychological side-effect of this dodgy signal-transfer method is NOSTALGIA, belive it or not. There is a distinctive "visual style", which now indelibly defines that period of computing and gaming. I would go so far as to call it a "Trademark of the Era" so to speak, just as much as the big blocky pixels, 8-bit music, and raspy 1-bit PCM sound-effects were.

For those who's eyes were spared the pain of such output, here's a short list of the various visual nastiness you could expect. It reads like the "Enemies / Point-Scoring Table" from the attract screens of old-style arcade games:

  • The Fuzzies
  • The Smears
  • The Fades
  • The Sparklies
  • The Wavies
  • The Ghosts
  • The Rollers
  • The Wigglies
  • The Zig-Zags

What do these mean exactly? A picture is worth a thousand words...

What you wanted to see...

The best you could realistically hope for...

I have a Dream(cast)...I have a Dream(cast)... The best case scenario, normally.The best case scenario, normally.

Aaaand, the crap you actually dealt with...

-- --
And, it just gets uglier...And, it just gets uglier... --
-- More ick.More ick.
-- RF scrambulationRF scrambulation
More crap?  Really?More crap? Really? Yes, really.Yes, really.

Each one of these symptoms/problems is a direct result of jamming what what was meant to be:

  • precise
  • digital
  • static/fixed-position
  • mostly-text output with
  • crisp-pixels

through a set of circuits in your TV, which were specifically designed for the exact opposite purpose! Namely, decoding and amplifying:

  • imprecise
  • analog
  • rapidly-moving
  • non-text images
  • and hiding the fact that individual pixels comprise the image!

Fortunately, there is a way to get good video output from the VIC-20. Start your propeller-beanies and get those soldering irons hot! Engineering to the rescue!

"Nurse, pass me the scalpel... and that DeWalt!"

Ok, time to open up my VIC-20 and go in for a close-look at how to fix this thing.

(...awkward pause...)

Er, before proceeding, I have to stop and confess something here; something a little bit embarassing and more than a little bit ridiculous. As I started taking out screws from the bottom of my VIC, I found myself feeling nervous and freaked out. After pulling out the last screw, I inexplicably hesitated, not wanting to open the plastic case. I think I was even hyperventilating a little bit.

Why?

Well, initially, I wasn't even sure myself. I've opened up and repaired literally thousands of pieces of equipment over the last 20+ years. I've performed troubleshooting and repair on complex military radar units, high-voltage power racks, HF radio transceivers, modern PC's, and so on. It wasn't a question of, "Could I fix this?" So why the heck was I freaking out?

Finally I realized I was nervous because this was MY VIC-20 we're talking about here, not some random, anonymous, grubby-old VIC that I picked up at a garage sale or off EBay for fifteen bucks. This was MINE, MY OWN, MY PRECIOUS. Yeah, yeah, I know... But it still felt weird, like I was going to "get in trouble" for tearing it open or something. I guess the nostalgia-factor is a more powerful psychological factor than I've suspected---it actually reverted me to age 13 again.

Deep breath... and slowly OPEN.

Fixing the Obvious... Problem #1 - Faulty Power Switch

Ok, this problem was easy to remedy. First, I opened the case, exposing the innards:

I can see the GUTS!I can see the GUTS!

Then I looked to see how the power-switch was installed:

The Troublemaker...The Troublemaker...

A trip to Frys Electronics secured an appropriately rated replacement. (The power brick outputs 9 volts AC to the VIC-20. The new slide-switch can handle 135 volts.) About 5 minutes with a soldering iron, another 10 minutes carefully drilling some small mounting holes, and VOILA!

Soldering in the leads.Soldering in the leads. Looks like it belongs thereLooks like it belongs there

Fixing the Obvious... Problem #2 - Heinous Video Output

Now to overcome the video nastiness; I wasn't about to tolerate such crap output. This is where the amazing quality of the documentation that came with the VIC-20 becomes apparent. Flipping to the appropriate page in the basic User's Guide:

5-pin DIN Connector (like MIDI)5-pin DIN Connector (like MIDI) From this, it was clear that I needed to buy a "Male 5-pin DIN" connector, and tie that into an set of RCA-plugs for a modern monitor/TV. So, while at Frys, I also bought a 5-pin DIN connector along with the new power switch. Then it was simply a matter of hacking up an old set of RCA-cables I had stashed in a box, warming up my soldering iron, and matching the physical wires to the diagram for the VIC.

You can get these off EBay for about $10-$12 if you're not handy with a soldering iron. But honestly, the connector cost only $1 and most people have lots of extra RCA-cables laying around.

The finished cable: Video + AudioThe finished cable: Video + Audio

All Systems GO!.... (Not.)

With everything soldered and cleaned, I closed up my VIC-20, plugged in my spiffy new audio/video cable, and fired up the machine. A quick blink of the TV screen and there it sat, shimmering in all it's luscious 8-bit glory, pulsing it's squat little cursor, silently, patiently, seductively...

It was... GORGEOUS. I sat for a long time, taking in the moment, just thrilling to flashback after flashback that the machine was bringing to me. Peace and contentment were mine... For about 5 seconds. Then:

"HEY! What the @&%$ is going on with THAT?!?!?

*sigh*

Watch the video for more gory details:

YouTube video of my VIC-20 powering on... with another problem.

Until Next Time

Thank you for reading everyone. I know this was a long post, but I hope you found it interesting. We'll get to the diagnosis and fix of this pesky problem in the next installment. Until then, keep your "To Hit" dice warmed up and your Staff of Healing close by.

Comments

Pressurizer (not verified)
An awesome read, thanks! I'm

An awesome read, thanks!
I'm a little confused about your DIY video/audio cable. I only see red and a white cinch audio plugs on one side. Or is one of those rigged for video? Interesting stuff, I wish I had more of a knack for electronics.

Shawn Delahunty
Shawn Delahunty's picture
Offline
Joined: 08/01/2011
Clarification

You guessed correctly---The VIC-20 default audio output is MONO. Hence I used one "channel/plug" for the VIDEO feed. In the alternative, you could get a 3-plug RCA cable, and tie the left+right lines together. You'll get the same sounds out of both channels, but at least it would be balanced.

Thanks for reading!

n/a
Mark Vergeer
Mark Vergeer's picture
Offline
Joined: 01/16/2006
hilarious, cool

Wonderful read!

n/a

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