0032 Why does this C64 keep blowing fuses? 

Get a Ray Carlesn PSU and call it a day.

x86 is overrated anyway

Huh, that's very interesting, too bad that you had power supply issues, I would just get a new power supply, as they are more efficient anyways, and should never have a problem with overheating, as the old powersupplies were just horrible with that- good thing it only affected the PAL chip and nothing else. Otherwise a voltage spike likes to kill ram chips especially, or other chips that aren't removable.

'shouldnt' be possible for the 9v ac to go severe overvolts as its ac direct from a transformer winding , or was it a 220v mains psu being run on 240? that'd make it high?

@@andygozzo72 Yes it is possible because whenever you turn on a load, it makes a peak voltage, sometimes twice the normal voltage. Multiply by, 1.414 and you'll get the peak voltage of 9v. Voltage regulator converts to dc.

I like to see what a "mega mail call" would be like! 😁👍

This is golden

One might argue that it's because it's about one item or two, which normally is, but then the previous one had 6-7, so not always that either!

It has my RF modulator replacement, woo

rf modulators shouldnt take much current, few tens of ma at the most, certainly with the UM1233 and UM1286

Right

I use a nail.

FWIW I used to work on telegraph systems with +/- 80v signalling current. It was not uncommon to short either to ground or to the opposite polarity. If it was a fused supply we would have been constantly changing fuses. Instead we used a ballast lamp whose resistance would increase with current. It also glowed to show a fault, much like your suggestion.

yep, its a very good idea when troubleshooting

Shango066 does this a lot when working on TVs

I kept hearing this Middle Eastern accent for some reason...

Install _us,_ comrade.

Install it in our air

Dang good idea!

Brass rod.😁

A DIP switch in a VIC 20? 🤔

@@christianlarsen1070 In the selectable RAM expansion board and not the mobo.

@@christianlarsen1070 In the 8K RAM Pack rather than the VIC itself - presumably to configure where it appeared in the memory map. I assume with some kind of expansion bus it’d be possible to have more than one. First computer, MK14 with 256 bytes RAM… 2nd, VIC=20 with 5K RAM + 8K RAM Pack… current machine have gigabytes - unthinkable back then!

Came here to say the same thing. Had a friend who kept blowing the fuse on a VIC-20, and it turned out to be this exact problem.

Yes, indeed. The smoothing capacitors will initially draw a hefty current as they are fully discharged, and the current will drop once they are charged up and the only thing drawing any current is the circuit; and this initial surge can be enough to blow a fast-blow fuse rated for the current drawn in normal operation. For the best protection you really need a slow-blow (T) fuse upstream of the rectifier (to protect the power supply in case one of the diodes fails short-circuit) and a second, fast-blow (F or FF) fuse downstream of the smoothing capacitor. But on a complex board, you can run into the same problem again with the combined charging current of all the little decoupling capacitors; so you either have to split up the power rails and use separate fast fuses for different sections of the board, or just rely on the fact that in the event of a fault, just by conservation of energy, all that current will necessarily be flowing through the slow fuse and it will eventually blow. The question of whether or not the slow-blow fuse provides sufficient protection on its own is then a matter of whether or not the (non-faulty) rest of the circuitry can withstand the upset on the power rails caused by the fault for longer than the fuse takes to blow, without permanent damage. I've worked in a job where we more or less used to have to do exactly that; we were making safety-critical controls for gas appliances, and they had to be constructed in such a way that no matter what fault occurred, there was no way to create a dangerous condition, even if a second fault were also present. You could rule out certain combinations that would be impossible (such as one set of contacts in a double-pole relay changing over completely but not the other; although you _do_ have to consider the normally-closed contacts opening but the normally-open contacts never making, because that definitely happens in real life if a relay is faulty or some power supply problem prevents the coil magnetising fully), but the type-approval rests on your proof, and you can get into a whole lot of trouble if something goes boom after you swore it wouldn't.

I'm glad I'm not the only one that likes to line them all up nice and straight when I work on a board. The A500 motherboard has some great ones to line up in the back.

The problem is, those leads really cannot take being bent more than MAYBE once or twice. So there's a half-decent change they'll just break off when you go to straighten them back up! Unless it looks really bad or it might be causing an issue I try to move them as little as possible. Or just remove them and put new ones in.

Or make music with it, that's always fun

Not sure if it has anything to do with smuggling, but the 2.5mm pin spacing is true.

@@Colaholiker OH, the Soviets did buy up advanced chips in the "west" during the 80s and I'm fairly certain that some of those chips had export restrictions on them, so moving them to the USSR was de facto smuggling. I have no idea at what scale they illegally imported chips but from what I understand computers were rare in the Soviet Union.

@@OscarSommerbo But if the West had export restrictions, which I can imagine, why should the USSR, who wanted the forbidden fruit, want to use a different pin spacing? It's not like western countries wanted to steal Soviet technology. 😅 I think it was just too "American" to use 1/10 inch, but staying in the general scale was practical, so they went metric.

@@Colaholiker The way I heard it, again I have no idea of the truth of the story. In the 80s it was fairly common to convert one inch to 25 mm as it was "close enough". I think I learned the "real" length when I was 13 or 14. So the Soviets designing computer components used the inaccurate 25mm for inch, by mistake or out habit, rendering a lot of hardware unable to fit western chips. So the reason was most likely a common mistake.

It was Metric vs Inch standard.

Pi3 is still very capable even with just 1GB of RAM. That is probably why purchasing a used one costs near as much as a low RAM pi4.

My bet is on bad power supply. There are a few reports of that same behavior around and I had the very same happen to me, tested on 2 systems with multiple fuses, with a brand new Keelog supply. Poof! Every time.

He assumed the bend was due to the shipping and could therefore not have caused the shorting. Seems like a reasonable assumption.

@@espressomatic interesting, I'd have thought that when it comes to AC voltage can only be zero if the coil breaks - not higher. Do we know what voltage that faulty PSU was outputting?

It's just double layer board, so if there's short of the trace, there'll be actual visible crack on the surface

@@danny8376 yeah That's what I was afraid of, was that he'd bend it in place and then Crack a trace open

I think the 8023 could also print as #6 and #7.

Well, if you buy a starter kit you can find RPI4s all over the place... at least in Denmark. ;-)

The RPI3 still makes a decent Retropie machine.

@@bsvenss2 I haven't been able to buy any RPIs at msrp in Canada for over a year... Scalpers are selling RPI4 for $300+

@@bsvenss2 Availability is not the issue, pricetag is the issue.

@@MrHurricaneFloyd An old small business PC is cheaper at the moment and far more capable. Rpi4 is going for over $200 here in Canada in listings, then higher when you make an offer.

shouldnt be possible for the 9v to give trouble as its straight off a 50/60 hz transformer, 5v is a different matter, you could wire a 5watt 5v6 zener across the 5v line in the computer to clamp any overvoltage

a filament bulb is a good current limiter

yep, bulbs are good current limiters, i use them all the time, you can make simple 'constant' current nimh chargers with them , i once rigged up quick n dirty trickle charger using a 25w pygmy bulb, with BY127 in series off the mains, it was only me that'd be going anywhere near it and i knew what i was doing..

Newer chips have a tighter tolerance for how much power they should draw.

@@jeffsadowski I don't think that matters too much for diagnosis, if it's even really the case. First, current draw varies most with activity, so dependent on what is going on (is something trying to boot). Also if there's really a wider tolerance on older chips, it's still small compared to the difference in current drawn depending on activity. In this case, the current might have differed because the reference board didn't have a modulator or had some low power chips installed where the original used higher power versions.

Could also have been a fast blow fuse. The big capacitors on the C64 mainboard cause a lot of inrush current. Especially if you use an 1A fuse, it should be a slow blow fuse.

More likely to have been 150mA. At least the digits look similar. It happens.

I made sure the fuse was the correct A. It wasn't the first time it blown it however I have no Idea if they were fast or slow blow ones. I also can't really check as they have been trashed moths ago (the package was sent out February).

@@danielmantione oh, yes! I wasn’t thinking much about initial capacitor charge as an issue. That makes total sense

@@krissy_h7854 fair enough! Thanks for replying here so I wouldn’t have to be checking back on the video! I totally understand how it is to not be sure of the details after this time, haha. Perhaps it was gremlins :)

It’s transistor

yep 2SD880 transistor, i think, metal tab is at a 'live' dc voltage

@@MrHurricaneFloyd Definitely got dropped or something got dropped onto it, but you need to pack your parcel to anticipate this. A couple of layers of bubble wrap to seperate a heavy 803 printer from a motherboard is not good enough. Cushioning completely around the printer in the form of packing peanuts, maybe double-box the motherboard. As a guide, pack your items so that they will survive a 2m drop or a 20kg item being dropped on top.

better to have bad packaging than to get thrown out!

@@austfox2170 I have used thin plywood to box items for shipment. I was getting free 4' by 8' sheets from a truck repair company that had a few 1/4" holes drilled in them. Replacement roll up doors were shipped on them, to prevent shipping damage and they were under 1'4" thick so it was lighter than multiple layers of cardboard.

yep, you can use acetone to 'melt weld' certain plastics ..

While this is true, IPA may however damage surface coating on LCD screens. Some of the anti-glare stuff can suffer, but that is really down to the individual coating they used. In my experience, it is normally not a problem, but I wouldn't bet on it.

@@Colaholiker delaminating MacBook coatings…

IPA 'may' affect some plastics making it crack/craze, i've had it happen

It's the 5V DC that goes out of whack. Especially if you use a newer VIC20 PSU on a C64, the 5V regulator can't take the extra load very long, but will burn out and then it can give anything between 6V and 12V which will cook especially the RAM chips quite fast. The 9V AC output can read a bit high or low depending your outlet voltage, but it is usually fine as it will be rectified and regulated for the parts that are picky. You CAN use a C64 PSU on a newer VIC 20 no problem as long as you have checked the 5V is in whack. Old VIC20 has just an 9V AC input and had all internal rectification and regulation, and required a roughly 30VA or higher transformer .

not a lot, though

I pointed my thermal camera at my screen and saw right away where your problem was ;)

Or in with a Pi for emulation inside the case. That's cool, I didn't know

Keyrah is unobtanium. Someone show me a link to buy one PLEASE!!!

I also learned how to test bridge rectifiers and voltage rrgulators. Thanks Adrian.

Yeah, on the early C64 boards, the 9V is used to create the +12 for the SID/VIC II but also a second 5v rail also used for those chips Supposedly a cleaner rail...So 9v is rectified, turned into higher voltage DC then run through a 7812 regulator for the 12v and a 7805 for the 5v. And yeah, it's funny when I'm running full screen to see a mouse cursor floating over the C64 image. (Or errors!)

@@adriansdigitalbasement2 Doesn't the CIA chips use the 60/50hz AC signal for timing?

Congratulations You are first

@@DaveMcAnulty yes they do.

The 9V AC is used for multiple purposes: One is that it is present on the user port for RS-232. RS-232 user port cables can use the 9V AC to generate the +12V and -12V for the RS-232 line drivers. The second application is the CIA clock, which counts AC phases. And indeed it is rectified to produce the internal 12V, 5V CAN and 6V tape power tails.

They are open source. The original EasyFlash uses 74 Logic ICs, an SRAM IC and 2 Flash Memory ICs all Through Hole stuff. The EasyFlash 3 uses mainly SMD components but also uses a CPLD and is much more powerful and feature rich.

@@RacerX- I thought the hardware was open but the software proprietary.

If you shorted a fuse, it wouldn't blow.

Indeed. They’re DIN connectors.

It is a Divoom Tivoo or similar, they come in different shapes and sizes

@@Ed64 Ah man, I should have known. I've got one of their little speaker things that look similar. Now I need to find all the Amiga Workbench graphics for mine.

After seeing the video this is my guess as well. Unfortunately I can't test it as I no longer have it.

shouldnt be possible for a 9v ac transformer to overvolt more than usual tolerances, unless made wrong, too high, to start with, or a 220v type used on 240v mains,

If it's transformer based, it might even have an additional winding for 110V operation

@@gigigigiontis8 Oh, that's a good point too! Yeah you might just need to change which transformer taps are in use.