Dead Commodore 64 with multiple faults repair - Shorted 9V, faulty video, strange keyboard input

An old and dirty Commodore 64 that was dead. No video, and a short on the motherboard.
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It turned out to have at least four different faults, and it took some time.
Can it be fixed ?
Part 1 of 2.
Part 2: • Dead Commodore 64 with...
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[@patkelley8293]

It's like you have one repair video to cover everything that can go wrong. I've learned a lot!

[@Arcticretro]

Thanks!

[@force4200]

Always so nice to watch have a nice weekend:)

[@Arcticretro]

Thank you! You too!

[@roelandriemens]

You might also check the zener diode near Q1, when Q1 was shorted between collector and base, it could be blown also.

[@Arcticretro]

Thanks. I tested it-it was good

[@itrema]

excellent work ! 20:55 i also faced to a screw that shorted a transistor. I isolated the metal plate of transistor from dissipator ( = ground ) and machine came back to life. I never understood why

[@Arcticretro]

Thanks :)

[@claudioquintanilla1471]

I would say 90% of those failures are false contact, rapidly you should suspect for IC socket base, just replaced it with round pin gold contact, putting a wire as a bridge wasn't too elegant, besides that light green socket already has bad contact issues... so soon or later more problems will come... another advice when you need extract a DIP IC first use a solder pump extractor (as you did) and then apply heat air gun noose over the entire body IC not only pins... because you will burn PCB as you did...

[@stevejakobsen2765]

If you are dealing with alot of shorts on theese boards you might find a milliohm meter usefull. You simply meassure resistance to ground. The closer you are to the culprit the lower the resistance..

[@Arcticretro]

Thanks for the tips!

[@congestiontv]

The case of this old breadbin looks as brown as my every day use one. Luckily mine is working just fine.

[@minombredepila1580]

It may be a short. Please notice that the two clocks in the tester screen do not match. Guess something is shorting one (or more) CIA pin(s)

[@HAGSLAB]

Nice troubleshooting, looking forward to next video! :)

[@Arcticretro]

Thanks 👍 Coming tomorrow :)

[@viperwizard491]

400C soldering is not healthy and will tarnish tip and burn components. Thin TAB 7805 is for low power dissipation. EEVBlog forum

[@Arcticretro]

Yes I know. I forgot to turn it down after another solder job

[@Doug_in_NC]

Wow, a 1540 drive! Those are pretty unusual, especially with the original ROM that isn’t compatible with the C64. As it’s next to a C64, I’m guessing it’s an upgraded one, right?

[@Arcticretro]

You will see it in tomorrows video :)

[@tommyvanpelt2408]

This is a far more valuable video than opposed to others where they go straight to the problems without any logical reasoning as to how to get there. Thank you! Also, greetings from Florida!

[@Arcticretro]

Thanks a lot. I've been to Miami. Great state !

[@Doug_in_NC]

I will second that. I much prefer repair videos with all of the wrong turns and mis-diagnoses than ones with just the correct solution. They are both more entertaining and more helpful.

[@eddielegs344]

Had to laugh again about you especially when you came with that Leister Fohn hahahA Worked 24 years with soon device was plastic welder. They are of good quality if you treat them well. What my colleagues sometimes did not do then they break down is a fragile heat spring in it. It is important that before you turn it off you put it on cold (turned) first let cold air go through and then after 5 minutes. Then turn it off. ! Looks like it's an old one to you. But with this method they last a long time. The spring is more expensive than the device. Also be careful with bumping or falling when it is hot and even more when it is cold. I had one in private once but it was confiscated during a drugs raid at a friend of mine's house and so were my belongings, including the Leister hairdryer. I had nothing to do with the drugs by the way. Hey but what a tough c64 this one would go crazy. What a disaster. But you're not giving up. Nooo, because there will be another part. 😅 🎉

[@Arcticretro]

We'll see :)

[@robf228]

So many problems with this C64!

[@Arcticretro]

More to come :)

[@salvocristaldi1689]

Waiting the second part to know the mistery ^_^

[@Arcticretro]

Working on it now.

[@stefanweilhartner4415]

maybe it helps if you add a bit of flux when desoldering?

[@Arcticretro]

Yes, I usually do that

[@wimwiddershins]

I was thinking, a short in the joystick ports?

[@Arcticretro]

Thanks, but it was not that:)

[@coryengel]

As you noted, moving Joystick 1 sends characters to the screen. Paddle controller signals are processed by the SID chip. Since the SID is performing poorly and characters are being sent to the screen, this could be at least partially a SID problem.

[@Arcticretro]

Thanks for the tips!

[@TotallyAqua]

Nice Storytelling. Keen to see if you can fix the board in part 2.

[@Arcticretro]

Next friday :)