Commodore VIC20 troubleshooting and repair with a budget oscilloscope

[@TRONMAGNUM2099]

Nice work on the repair. The pocket scope worked well. You've been showing computers that I don't know too well so that always makes for better viewing.

[@robbyxp1]

Perfect retro computer video. Just good old fixing. Thank you.

[@mikehorner517]

Excellent video. Very easy to follow along and very informative

[@davidkroeker1821]

This so much for this video! I received this exact oscilloscope for Christmas and am restoring a VIC 20 that was found in a dump nearby. It turns out this VIC 20 just totally worked, despite having been thrown out and spending at least some time outdoors. It mostly needed a good clean, a 2 prong power supply, a 5-pin video cable and replacements for 3 missing keys. But, your video has been really helpful in teaching me how to use this scope on my working VIC 20. Thanks especially for showing an example of when you'd use both channels. I hope you'll use this scope again in your videos!

[@TheRetroChannel]

It's a handy little scope for sure. This video probably wasn't the best example of how to use it, but it probably feature quite a bit from now on. Well done with the VIC20 find

[@commodorecave5581]

Interesting video. Nice to see a Vic20 revived. Well done.

[@NickNorton]

My second computer was a VIC-20. (1st being a ZX81) At the time, I craved for something with an 80 column display. But I could not afford anything like that. 24 Bit depth RGB displays were rocket science back then and everything including my basic VIC-20 felt like a portal to what if...

[@MindFlareRetro]

Wow, that was a grimy one. I enjoyed watching your troubleshooting process and picked up several new things to watch for. I guess you can never have too many socketed DIP ICs 😜. I picked up the same thermal imager (Uni-T UTi260B) that you have - a b-day present to myself - I keep seeing yours on your bench and had some serious bench tool fomo. It's a super handy tool.

[@TheRetroChannel]

Oh yeah, super handy tool. Shame it didn't come in handy for this repair, but it will still be used to work out which chips to chuck a heatsink on. Not sure if you also got the macro lens for it, but that's been really handy too, especially for components that are clustered together

[@granpawa]

Great video (as usual). Those tiny scopes can be surprinsingly useful in some cases, especially when working on old (ie slow) computers. A side note about testing logic chip in the TL866 : you can only trust the result 100% when it's detecting a BAD chip. A "good" one can sometimes only work at the low frequency the TL866 tests it.

[@TheRetroChannel]

Good point. I've had cases where the logic tested good on the first couple of tries, and then bad and good again, so I usually hit test about 10 times. It's not perfect and probably another excuse to finally get the retro chip tester pro, surely something will come up soon that will leave me wishing I had one

[@jeremyshull8850]

Awesome video! I have a vic-20 and commodore 64 from my childhood and wanted to restore them. The vic is dead, but with your techniques I spent time troubleshooting and think I have good understanding of what is wrong and have a part on order. I honestly wouldn't have been able to get this far without your video. Then I turned to the commodroe 64 - I blew the sound in high school when I made an audio amp circuit, did something wrong, an amp cap blew up, and the commodore didn't have sound anymore. So being inpsired to figure it out, I looked at the SID chip on the scope like you did on other chips, and it looked good. With that looking good, I figured it was the output transitor. Swapped it out, and it works again!!

[@TheRetroChannel]

Fantastic. Congrats on getting the C64 working, hopefully you'll have the VIC-20 back up and running soon. And thanks for the super thanks, I really appreciate it. Cheers!

[@Walkera22e]

Just found your channel and it was an instant sub.. Nice video.. I repaired five VIC20 boards a while back and 3 of them had a bad Basic ROM so I put my money on the Basic ROM quite early in the video :)

[@senilyDeluxe]

Pulled one out of the e-waste container a few years ago, also black screen. I had the luxury of a working machine and many chips socketed on both, so I could just swap chips around. On mine, just the kernal ROM was bad.

[@TheRetroChannel]

Score!

[@MoreFunMakingIt]

Cracking video Mark! This one will be super handy for me. Got a black screen Vic20 in the next bundle of broken machines. Totally feel your pain at the end there. Its heartbreaking when you forget to record something you just cant do again (or don't want to!)

[@TheRetroChannel]

Thanks mate, good luck with the VIC20s. I've got a couple more to look at, so it will be interesting to see what other ways they can break, both yours and mine. Oh yeah, forgetting to hit record caused some grief as it also meant the VIC20 capture didn't get recorded. So the video capture that you see from the VIC20 at the end was reshot and added in post, good thing I didn't type anything or fire up a game 🤣. It was either reshoot the whole scene and fake my reactions, or fake the capture and keep my reactions and stuff ups genuine

[@naderhumood1199]

V informative, thank you v much.

[@eugenekiselev]

cool! thanks a lot for this video. As usual a lot to learn (I'm struggling with black screen on one of my three plus/4, two of them I fixed easily but got stuck with the last one)

[@tenminutetokyo2643]

Jam in the tiny new TDK box film caps and get rid of those big old chicklet film caps.

[@dragdusan86]

Great video as always! 😊 Thank you for alawys teaching us electronics and troubleshooting as well through you videos👍

[@Nimmbin]

Great video. Thanks for sharing 😁

[@Doug_in_NC]

The BASIC ROM is a well-known failure point on VIC-20s with blank screens, at least if you are experienced with them. The easiest way to check if it’s the cause is to boot up with a game cartridge that boots from switch on. The VIC 20 attempts to boot from a cartridge before going to BASIC, so it will boot to a game with a defective BASIC.

[@ray73864]

I swear, you have more luck than I do with getting retro things that are broken :( So far, out of several things I have bought from eBay Australia (3 x NES, 1 x Vic20, etc...) only 1 NES has been rather dead and needed extensive repair (All things sold as 'for parts or not working'). Really really hoping this C64 that I scored last week that The Salvos in SA was selling on eBay as 'For parts or not working' requires more than just a clean, though the screenshots showed a missing key, so that's something I guess :P The Vic-20 needed a retrobrite and some new clips printed (found them on Thingiverse by The 8-bit Guy's brother).

[@TheRetroChannel]

Arrgh, hate it when they're listed for parts not working and they work, it's false advertising I tell ya. We should be well within our rights to lodge a dispute with eBay. I do wonder how eBay would respond 😄

[@ray73864]

@@TheRetroChannel I get why they do it, they are trying to get around the fact that the item might arrive not working and you could claim 'not as described' on eBay. Sort of a 'get out of jail' free card for the seller. It's just frustrating, these sorts of things don't always come up, and when they do, they end up really expensive. I managed to get the C64 for $210, plus about $40 for postage from South Australia to regional WA, kind of hoping it actually is broken so that I can do more than just recap or clean it.

[@Jimblefy]

Very cool. Thanks :)

[@ingmarm8858]

26:40... um, yeah nah lol. Unless you see all the 138 select and enable lines in their required states at the same time (ie more channels on CRO or on LA) you can not assume that select line will be toggling :-)

[@TheRetroChannel]

Hah, yeah that occured to me later on. Turns out I was barking up the wrong tree anyway

[@davidtwist3659]

Correct unless the cpu is addressing the ROM then the output will be high. It depends the code being run.

[@fu1r4]

20 hex = space

[@andrew1977au]

Farrrrk hahahhah

[@Jkauppa]

not free open fully accessible standards are trash

[@Jkauppa]

including all ISO standards

[@Jkauppa]

no exceptions

[@Jkauppa]

if only the pcb's were direct socket on the pcb, like laser engraved on the copper, no soldering required, just surface mount in the pcb-copper-socket directly

[@Jkauppa]

why do you sound like a dentist lol

[@Jkauppa]

electricians