2021 C64 Repair-a-thon #4: "Yes, I've Had my Tetanus Booster."

Welcome to my 2021 edition C64 repair-a-thon! In this video, I work on and fix machine #5 and a bonus machine #6. (A VIC-20)
Part 1 / Machine #1: • 2021 C64 Repair-a-thon...
Part 2 / Machine #2: • 2021 C64 Repair-a-thon...
Part 3 / Machine #3 and 4: • 2021 C64 Repair-a-thon...
Part 4 / Machine #5 and 6: This part!
0:00 Intro
0:55 Machine #5 - C64
10:52 Machine #6 - VIC-20 Rev D
31:55 Outro
-- Video Links
Support the channel on Patreon:
/ adriansdigitalbasement
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Zimmer's VIC-20 Schematics
www.zimmers.net/anonftp/pub/cb...
My video on damage-free chip removal:
• How to remove chips wi...
Jonard Tools EX-2 Chip Extractor:
amzn.to/2VazxDS
www.jonard.com/Products/EX-2-...
Wiha Chip Lifter:
amzn.to/3a9ftWw
www.wihatools.com/precision-c...
Link to desoldering video
Sven Petersen's Github (for the Diagnostic test harness files)
github.com/svenpetersen1965
C64 diagnostic ROMs (including Dead Test and regular diags)
blog.worldofjani.com/?p=164
8-bit Dancy Party:
csdb.dk/release/?id=200763
- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.16...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.com/products/digi...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress.com/item/33000...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/itm/TS100-65W-MI...
EEVBlog 121GW Multimeter:
www.eevblog.com/product/121gw/
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/itm/USB-Logic-DS...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfreight.com/4-inch-...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/itm/14-16-18-20-...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/itm/1-2-5-10PCS-...
Heat Sinks:
www.aliexpress.com/item/32537...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=r...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorecomputerclub.com/
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[@3vi1J]

"Obviously this machine has been exposed to a lot of moisture". Yes, in Louisiana it's called "the air".

[@SonicBoone56]

Ikr. That's the deep South in general. No need for a sauna, just go outside right after the sun comes out after a rain storm.

[@Varangian_af_Scaniae]

I don't know how horrible is to live in high humidity environment. I have the exact opposite problem. I have had 20-30% humidity in my house this winter season. That is unpleasant. Bought a humidifier, got it up to 50%, was lovely. But our water is full of lime so instead of low humidity my house is now covered in white dust..:P

[@nickwallette6201]

Yeah, after living for a couple decades in cold and low humidity, I love visiting the south. First thing I do when I get there is sit in the car with the AC off and let the humid heat bake into my bones.

[@SonicBoone56]

@@nickwallette6201 heh.......I wonder how it is with the dry air up north? The humidity here is unbearable once May hits.

[@IsaacShoebottom]

@@Varangian_af_Scaniae Have you tried filtering your water first?

[@johnsonlam]

About the VIC20, I see "Assembled in Hong Kong", a bit history things, back in the 80's we have lot of girls (lady) in the factory assembly line making these computers, when running out of parts, their supervisors have to make sure the order can be completed within deadline, therefore the long fuse and other shoddy modifications may be the direct order from the management, "quick, look good and working" is very common Hong Kong style until now.

[@MatthewBarras]

Hey small world. I went to St Mary Parish schools at the time these were around. The only computer classes were in High School. The labs usually had 30 Apple IIs of some sort. Just taught simple Apple Basic. In 1988 the IIs were replaced with IBM 286s. The High School Library had one Commodore for student use. If I remember only the cheerleaders and teachers used it. They had an OKI Data printer that printed black AND red ink on tractor feed paper. The cheerleaders would make banners for school games. Teachers would make hallway flare. It could well be a central office computer also.

[@SonicBoone56]

Gotta wonder if the rest of those old computers are in the trash somewhere. I'm from South MS lol.

[@danilko1]

Could this be that library Commodore?

[@piconano]

The power of galvanic corrosion. When two dis-similar metal are in contact in the presence of humidity, you get what you showed.

[@pb7379-j2k]

I came here to say that. For the few socketed chips in the Vic. It’s good more weren’t socketed!

[@samivorhees]

*runs straight to the cat: "Oh and this kills you too"😂

[@macdaniel6029]

Ha! Finally an RF shield Adrian can´t throw away ^^

[@sonicunleashedfan124]

There was one on the mystic modded color classic

[@stevethepocket]

And of course it's the one that's in such horrible condition that even the hardcore preservationists among us would want to.

[@craftsman123456]

Standard Sparkle bug on the Silver Label. A bug in the original Character rom. A Silver Label will also fail the Control port test even with a working SID. They had different resisters on the motherboard. Nice to see a Vic on the table.

[@IanSlothieRolfe]

Fun story: Back in 2005 I was between IT jobs so I went to work with a friend cleaning and maintenance in a factory that made hose clips. I was told to clear out a load of junk from one corner of the warehouse which seemed to be mostly computer cables, old binders and other office junk. At the bottom of the heap was an old VIC-20. I asked if I could keep it and the answer came back next day saying I was welcome to it. I learned that it had been used in the goods in area connected to the company computer and used to have a cartridge in it that contained the (proprietary) software, a (presumably serial) computer interface and a barcode scanner. It was used for booking in goods coming into the warehouse. It was completely fillthy; when I took it apart it was full of soot from the exhaust of the lorries that reversed up to the loading bays of the warehouse! As I tried cleaning it up I quickly realised that something corrosive in the soot had attacked the components and they started dropping off the board. The soot also had eaten away at the PCB so the poor machine was a write-off. Someone I knew needed a keyboard but the rest got binned sadly. I suppose if I had known what I do now I might have extracted the VIC chip from the board since it might have been protected by the sheilding can, but to be honest in 2005 they weren't particularly rare. I've since found out that commodore sold a lot of VIC-20s to companies that turned them into industrial controllers (I think the 8-bit guy did a video once about it) because they were cheap and the cartridge port allowed custom boards to be plugged in easily, a sort of pre-arduino!

[@samuelattas3864]

wow a pristine first gen. C64! Actually my school had a computer room with ten or twelwe bread bin 64's each with a 1541 disk drive and 1702 monitors, as well as two needle printers in the back of the room. Then we would share a computer among two pupils in computer class. They still had them when I graduated from 9th grade in 1993 :o)

[@HeffeJeffe78]

"Oh look, there's nothing wrong with this machine." .... Adrian grabs hammer...

[@JoaoVitor-cw2vg]

I was expecting something like that

[@cleetusmacfarland9453]

or pushes the earth shattering kaboom button!

[@CezaryAkakios]

Adrian, there is a simple solution to the bad DeoxIT spray can. That design with the large yellow straw is called the "perfect straw" by the manufacturer, but that's one of those 'improved' designs that is actually made worse. People complained so much that DeoxIT sells a 'classic' version of the can, part number *D5S-6-LMH* . This one even has a variable flow design, where you can rotate the nozzle to achieve low, medium, or high flow rate, which is what the -LMH suffix alludes to. This design is your standard "Red straw" type nozzle that is found on most other products. Due to the adjustability, you can set it on the Low flow rate and you do not have to worry about a bunch of extra liquid accumulating anywhere, and there is no bulky plastic shrouding for it to accumulate in even if it did leak. Highly recommended to seek out this part number. I bought mine from Parts Express and it was about the same price as the yellow straw version.

[@adriansdigitalbasement]

OH thank you! I'll definitely be ordering the D5S-6-LMH version next time -- this one is just atrocious and horrible!!! And yes I would really like having low flow -- as most of that time that's all I want.

[@jeromethiel4323]

I swear, retro tech is my ASMR. Love these, as i was poor back in the day, and could not get the hardware i wanted.

[@CamiTheWitch]

The "Short Board" VIC-20 is usually called the "Cost Reduced" or "CR" model :)

[@enzofitzhume7320]

TIP: I spray a little DeoxIT 5 before I remove a crusty old chip from a historical motherboard. It does minimize the crunchy removal sounds. Spray a little D-5 on the chips, wait 5 minutes and your chip should come out much easier.

[@Axess-sv8nq]

Wow! That VIC-20 looks like it was in a garage - or outside shed - for YEARS!

[@nefaurora]

The name of the Music Song on the Vic-20 and also C-64 Radar Rat Race Cartridges is "Three Blind Mice"... An old Children's song.

[@MajorMacca]

That Radar Rat Race game is basically just a clone of the Rally-X arcade game but with cars and flags changed to mice and cheese to avoid a lawsuit... :-) In the arcade game it would be smoke you fired out of the rear of the car to blind the cars chasing you so how this translated into sparkles coming out of the mouse's behind took a major stretch of someone's imagination...

[@esmerylan]

Also it looks like they didn't copy the movement of the enemy cars in Rally-X very well- from what I recall (and it's been a while since I've played Rally-X), they didn't mirror the player's movements the way these rats do and would instead take paths around to cut the player off.

[@iguanac6466]

Rat farts

[@MajorMacca]

@@iguanac6466 Ok, maybe not that much of a stretch of the imagination then... :-)

[@MrDjada80]

he is , what they call a "lightning god" . just too modest to admit it.

[@DaveVW]

So glad to see Vic-20 and ways of probing to test if processor and bus signals working. Congrats on fixing!

[@Zeem4]

Rather than spray paint, it might be worth investigating vinyl dye for recolouring yellowed plastics. I believe that it chemically changes the colour of the plastic rather than sitting on top like paint. I saw some discussion of this on an Acorn computer forum, where someone successfully recoloured a yellowed BBC Master.

[@iamdarkyoshi]

Glad to be a patreon!

[@OQTIZZLE_ORLANDO]

Glad to be a patreon ][ ! LOL

[@SimonZerafa]

"Yes, I've Had my Tetanus Booster!" might be another good T-Shirt slogan! 😁 If there are any artists that want to have a go a T-shirt designs please let me know.

[@adriansdigitalbasement]

I'm changing the title of the video to include that quote!

[@frogz]

@@adriansdigitalbasement you should make a shirt!! i forget if you have merch yet but redbubble lets you toss a design up within 30 seconds in some cases, someone made a comment on facebook and i turned it into a tshirt design within 29 minutes of them posting "this would make a good tshirt design" about a very 80s science diagram

[@pompshuffle562]

@@frogz I guess redbubble doesn't have very good policies, lgr had a bunch of stickers on his store that he designed himself and apparently someone falsely reported them all and they just took everything down without telling him.

[@hernancoronel]

Awesome! Another video from you before ending the weekend! Thanks!

[@floydfix420]

The yellowing of plastics is due to heat and not ultraviolet light as everyone thinks. I have used a Sous vide machine to submerge my peroxide covered and bagged items to "retro bright", no lights needed. Hence, the reason why you find such weird yellowing on some items in areas where the sun couldn't possibly get to. Keep up the great content. Love watching your videos.

[@brobryce64]

I get a lot of inspiration from your videos! Thanks for keeping us fellow hackers growing and learning!

[@sefmonsta]

A new discovery for me: desoldering needles... not solder syringe, but stainles tubes that help remove corroded or stubborn pins. Might be worth checking out for those rusty parts!

[@sebastiankrosinger2101]

I especially love your C64 repairathons. Learned a lot... again. Thank you very much!

[@gregjarvis1232]

I think the rats in the Vic 20 game where chasing after the extremely yellow Vic 20 case🤣

[@Walczyk]

i think an update video involving paddle controllers and what exactly is causing the test to trigger bad would be very interesting, it's mysterious

[@dhpbear2]

VIC-20 Ratrace: A poor man's Pac-Man!

[@pyromiko]

i love this channel. greets from Argentina!

[@GrantMeStrength]

The VIC-20 game is pretty much Rally-X, which I do like ;-)

[@colinstu]

Gratz on 100k!

[@minty_Joe]

So, Adrian, are you gonna call C64 #5 "Johnny"? Ha-ha-ha! Just a Short Circuit joke, there. "No disassemble Number 5! Number 5 is alive!"

[@ownpj]

12:35 CR or Cost Reduced is what it's known as.

[@danilko1]

Vic 20 story: As part of a student exchange program, I was in the Soviet Union before its collapse. In one medium sized town, in what could only be described as a department store, they had a Vic 20, with monitor, disk drive, and printer, marked for sale, at 20,000r!!! The official exchange rate was 1:1 $1 US to 1 Ruble. The unofficial black market exchange rate was $1 to 10r. The year was 1990. I can only guess, this was for show, not for foreigners. The town was far from touristy areas. This was for the people - You can get a computer, if you want one. It was impossible to save for. For perspective, this was 200,000 loafs of bread, worth. Meanwhile, government run, after school programs, for party children, had clone Apple II computers, made in Bulgaria and with Cyrillic font, to learn basic programming. The USSR was kinda of weird that way. They wanted Western technology, even Pepsi, but didn't want to pay anything for it, officially. Then turn around and make it impossible for regular people to access. Also, the only way to get a bottle of Pepsi, was on the river speed boat, which was a form of mass transit.

[@rarbiart]

18:40 i have no idea why you don't apply deoxid first before removing the DILs. breaking oxidized pins in that case is more intentional than accidental.

[@yoopeek]

With the help of your advice, I have repaired my Commodore 64!

[@ferrellsl]

That VIC-20 gives tangible meaning to bit-rot.

[@Rezendes]

So I just watched this and it reminded me how extremely overdue you are for having a Retrobrite Episode! Please please please do a retrobriting episode, I think it will be excellent. You always put so much effort into restoring these older machines to perfect original function but the yellowed plastics are like the machine is crying when instead it could shine and smile.

[@stevethepocket]

It would be a perfect opportunity for someone other than Retro Recipes to try doing it without peroxide. Although he does live in Oregon, so he'll only have a few sunny days out of the year to work with. 😉

[@mikekopka344]

Adrian, This is going to be a bit wordy so sorry ahead of time. First off I thoroughly enjoy these videos, especially when it comes to the Commodores. I have had various of computers growing up starting with the Tandy TRS80. I was big into electronics and programming my own stuff. I did a lot of different projects on my C64 from basic home automation to robotics to voice synthesizers etc. One of the last projects I was working on but it was only in design phase was reviewing schematics and various other electronic projects, working on researching the clustering of the C64s together. I had quite the "museum" of vintage game consoles to vintage computers parts and accessories not to mention my vast electronics workshop with equipment parts and tools. I was deep within my research of clustering the C64s but in the early 90's we had a freak flash microburst where we got nearly 2" of rain within an hour and my basement was completely submerged. I lost everything!!! The stuff I lost, if you only knew, you would have probably cried. Long story short I lost interests in electronics and programming etc. until coming upon your videos which resparked the interest. So I am writing to you today to offer a suggestion for your channel, if you are anything like I was you probably have a stockpile of electronic components wire etc and breadboards. Perhaps you can do a video series on trying to cluster C64s together to make a more powerful robust singular compute power. Unfortunately my vast research notes are long since gone and a faded memory until watching your repair-a-thon series which jogged the old memory. Maybe one day I will start my research over or perhaps not, I have been out of electronics since the 90s and I have forgotten more than most know about electronics. Any rate if you do take this on it will be one interesting video series.

[@GORF_EMPIRE]

I would gladly take that ugly VIC-20 just to have one again. Good job making it work!

[@herdware]

I think they are called VIC-20CR (Cost Reduced).

[@danielson9579]

Great video 🙂👍

[@NilsRetroHobbyRoom]

Shocked at first hearing no „let‘s get right to it“ but furtunately Adrian saved the day 😂

[@memadmax69]

"Yes, I've Had my Tetanus Booster." OOOOooooo, clicks on play as fast he can. ^.^

[@amigacoverdisk]

Nice series, thanks! Some more Commodores given a new lease of life!

[@OQTIZZLE_ORLANDO]

Glad to be a patreon ][ !

[@al.d9592]

Man, luckily this time we weren’t playing the drinking game! Great video, as always. Never gets boring

[@jtveg]

Thanks for sharing. 😉👌🏼

[@Choralone422]

Oh my! I remember playing Radar Rat Race on a VIC-20 way back when! It along with the Fairchild Channel F were the first video games I ever played at home!

[@johns.7609]

That poor VIC. I found myself making inappropriate crystal meth jokes when you pulled out those decrepit MOS chips.

[@rdh2059]

Regarding the deoxit cans, the problem is the nozzle itself. When you flip up the precision tube, it tends to not be a tight connection and backpressure causes the liquid to back up into the cap.

[@Doug_in_NC]

Great to see you doing some repairs on a VIC20! Like you, I had one as my first computer, and I remember it with affection even though it really wasn’t that great compared with a C64.

[@iguanac6466]

I remember envying my friend's C64 with it's amazing SPRITES! heh

[@rodhester2166]

those old games always make me laugh... lol

[@MadManDarkJedi]

Happy ending, nice..

[@pa4tim]

I spray the guts of those cans in a little jar and use a brush, pipet or serince to apply the stuff. Works much better. I had an industrial board last week and I was testing chips with a scope like you , all seemed right but it was not working. I used the HP current tracer and found out one of the groundpins did not carry current. ( I had a working board for comparing) On of the first things I learned from my " mentor" is to look for current ( using a probe or , in analog electronics, measuring the voltage over resistors. ( I now sometimes use a 7,5 digit meter to measure the voltage drop over a trace :-). Current can tell you so much. I always watch the current of the supply with a separate meter in the rare cases I can not use a lab supply.

[@stevesmusic1862]

Adrian. Its the arcade game Rally X. Very good version!

[@paveloleynikov4715]

That LS replacement definetly look like not only missing three legs, but also has crooked casing.

[@WarnerVH]

My home town is in St. Mary Parish and went to school in the parish in the 80's-90's. The location is home to "cities" such as Franklin, Berwick, Morgan City, Patterson etc..... Good video. New to the channel. Definitely giving the channel a look over for more informative videos.

[@daekwankim]

OMG that music. It kills my soul

[@michaelcarey]

I think the corrosion issue would be electrolysis. Any dissimilar metals that are touching (like the IC pins and the IC socket) will suffer galvanic corrosion in the presence of an electrolyte. They might be very close on the galvanic table, but unless they the exact same metal/alloy you will eventually get corrosion.

[@DerekWitt]

Holy rusted ICs, Batman!

[@Dukefazon]

12:45 - judging by the title of the video it makes me anxious just looking at your waving finger around the rusty shield, bracing for impact :D Since only the socketed chips are rusted, maybe it's not the chips' fault but it's a low quality socket that somehow reacts with the legs of the chips.

[@commodorebench2556]

I'm pretty sure I've commented this before, but the for the paddle inputs, the diagnostic is looking for a narrow range of values and sometimes replacing the two 1800pf capacitors can bring this back in range.

[@domramsey]

Love that these poor mistreated machines still work with basic fixes. I'd love to see you do a full cosmetic cosmetic restoration of some of them. It would be sad for that Vic-20 to sit unused on a shelf for another 40 years just because it's a bit battered. 🙂

[@ccronn]

"I just want to play the game to make sure there's no graphical corruption...." Sure, thats exactly what I would say too...

[@gordoncreAtive]

You could restore that reset switch on #5 alongside with the proper circuit that you mentioned.

[@chuckherndon3251]

Seen C64s with that same deep and internal yellowing (browning). On the 64s I see like that, the ones that have turned pretty much orange, I've restored the original color, as close as I can by retrobriting (regular water and peroxide, covering the object) with UV lighting. You've got to pay a lot of attention though, as with these extra colored ones in particular you can overdo it and they'll get white blotches. I check every 30 minutes and have had a lot of good results and a few misses, also a few that just won't brighten fully.

[@nickwallette6201]

Man I loved Radar Rat Race as a kid! :-D

[@kardeef33317]

I had a Vic 20 as a teenager. I had the 8kram expansion, a cassette, 300 baud modem and radar rat race that games music is just 3 blind mice played in a loop.

[@rollingrene]

Nice video ty

[@tmilker]

Not too surprising those legs fell off, that's what happens when you pick up dead bugs. 🤣

[@snarfusmaximus]

I had two VIC-20 machines go through my hands many years ago and I had traded them for other computers that I found more interesting at the time. Every time I see one in a video, I wish I still had one. Now they cost actual real money but back then they were worth peanuts.

[@DavidWonn]

The disclaimer in the title seemed odd at first, but then it made sense at the end of the video.

[@aaronrowepalmer]

I spit my coffee out at the title!

[@disposablebasterd]

My recently restored Vic looked like that as well, it retrobrited really well though It wasn’t deep stained. If it were me I’d paint it some other color than cream. If you’re gonna paint it have fun.

[@nefaurora]

Nooooooooo....We need more C64 Repairathons!!! How about a Vic-20 Repairathon next.....!??!!!!! Keep up the great work Adrian!! :o) Tony K., Melbourne, Florida...

[@SantaClaw]

Yay!

[@scharkalvin]

RETRO BRIGHT !!!!!!

[@InsanePsychoRabbit]

_Clostridium tetani_ does not spontaneously generate from rust. It is a soil bacterium. (Sorry, I am a pedant)

[@spagamoto]

Surprise AVGN reference!

[@peteregan9750]

so do we get a cleaning / retro bright etc. vid :P

[@rarbiart]

11:23 that looks like really tasty cheddar cheese!

[@JVHShack]

"Number Five is alive"

[@TheFurriestOne]

A little evaporust would clean that RF-shield/motherboard-mount right up! (and maybe the sockets too? Better to just replace those, really)

[@kardeef33317]

Even was on a BBS in the mid 80's a little because it cost a ton .

[@richards7909]

Radar Rat Race. Many in hour played on that.

[@marcgforc3]

Never trust the rust ! something rusty and crappy just needs sometime a litte bit of attention and love to work again !

[@laxr5rs]

Key phrase, "that's going to cause a problem." heheh

[@giuseppelavecchia775]

il C64 e in condizioni buone,ma non ho mai visto un VIC20 in quelle condizioni,lo shield sotto la mainboard pieno di ruggine,tre chip marci e il case talmente giallo che sembra verniciato in giallo.il padrone del VIC20 lo ha tenuto nel peggior modo possibile.sono contento che li hai sistemati,sei un ottimo tecnico.ciao

[@olepigeon]

It's a shame that many of the MOS chips were so unreliable. I love that MOS logo. If I owned a C64 or Vic, I'd want all my chips to have that MOS logo. :)

[@danielmantione]

Yes, I'm always replacing them with mixed feeling, because those chips tell a story: That Commodore made their own chips and were capable make stuff themselves if they had supply problems. Replacing them with standard parts removed that history from the machine. In 100 years from now, if there are people around interrested in computer history, they will for sure like those chips in there. But... a machine should always be repaired, so there is no alternative for replacing them with standard chips.

[@dhpbear2]

2:50 - If you *did* repair it previously, how did you overlook that added switch?

[@parrottm76262]

Wow! Just seeing those rusty legs on the ICs was worth the price of admission! No! Not that Rat Race song!

[@awebuser5914]

Great C64 fix-it series and here's a weird one... (don't have any test carts yet) I have an NTSC C64 breadbin that was starting on a black screen. I started swapping known good PLA, etc. and minimizing ROM(s) when testing with a game cartridge. If I pull the character generator ROM, game cartridges load OK (with some, expected, messed-up areas), it also boots to BASIC, but with garbage all over the screen (as expected) But if I replace a known good character generator ROM, it goes back to black screen on power-on and cartridge games no longer boot! Are there any external logic chips (other than the PLA) that might be the culprit? I'm in the process of making a ZIF-socketed motherboard, but it'll take a while for the sockets to arrive!

[@Polydeukes68]

I would never clean or overpaint yellowing that cool (the VIC20). That is history right there! Its sad how often "restoration" of retro computers is nothing like restoration, when people throw out parts, shields etc. the computer is no longer orginal, its a mod which is not worth anything historically.

[@DanielM111]

Mmm, crunchy chips!

[@Fridelain]

I'd solder some legs on those chips (plenty of flux, some light sandpaper action before). Maybe solder them directly to those sockets that come in strips you cut to length.

[@Fridelain]

@Simr Khera I'd do it for the joy of it.

[@theatheisthammer]

@adrian you should use a green shape for good chip orange for working but faulty and red for dead 👍👍👍

[@PixelOverload]

My best guess to explain the degree of that vic20's yellowing; it may have spent much of it's life on a glass counter in direct sunlight that reflected off something below the counter into the vents on the bottom of the machine, reflected back onto the inside of the bottom by the RF shield while protecting the inner top, immersing the bottom half with UV rays from all sides

[@bruwin]

Doesn't explain why the when the plastic was broken it was also yellow inside though. The break on that standoff looked like it was fairly recent, and it was uniformly the same color as the rest of the plastic. So even if it was reflected uv, and the standoff had broken off ages ago, you'd expect some variation in the color.

[@PixelOverload]

@@bruwin photodegredation doesn't simply stop at the surface layer, it's a chemical reaction that slowly permeates the material, in this case from both sides and apparently quite intense. The process would have also released more free oxygen trapped in the bottom of the case accelerating the degredation, and likely also causing the excessive rust