Thorry84 @ Thorry84 @feddit.nl

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14

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1,283

Joined

2 yr. ago

Function generators have come down in price so much the past 10 years or so. In the past a good function gen was a very specialized expensive piece of kit. These days you can get a pretty decent unit for not much money at all.

When I first got this monitor powered up, the vertical deflection was totally collapsed. Turned out two transistors were acting weird. They weren't broken exactly, but not acting like they should either. Without a function gen I would not have caught that as quickly as I did.

Wow that's awesome man. Glad you added the 'since childhood' part, I was feeling a bit old.

I've fixed up a lot of CRTs, but this one is kinda special, since it goes so well with the MSX system.

Yeah totally correct. The CRT is only the tube part, the whole thing is the monitor. But when I call it monitor people automatically assume it's like an LCD. So I would have to call it CRT monitor, but that's a lot.

I will post a vid of the thing if people care.

Edit: Posted it https://lemmy.world/post/20980504

Yeah the pot is fine, that was the first suspect. Cleaned it and even thought of replacing it, but it measures just fine.

I've found several versions of the service manual and combined them to get the info I want. Both seem to be parts of a larger manual, which I can't find.

I've been probing and scoping for hours over the past months. But when the CRT is apart that's kinda hard, since it has a lot of high voltage I want to avoid. No worries, I have the tools and the experience to work with these things. Over my professional and hobby lifetime I've fixed over a hundred CRTs and worked on/designed/built hundreds of other electronics.

I took out a couple of transistors (this thing is almost all discrete components, no integrated stuff) in the horizontal deflection path and tested them and they seem fine. I hooked them up to a function gen and a scope and tested them within parameters. That's how I found and replaced two other transistors that were dodgy and bringing the thing back to life to start with (it had fully collapsed vertically).

I checked every component in the horizontal deflection path and they all seem fine. And since the thing works most of the time, I suspect they are fine. It might be mechanical, but I've tapped all around and that does nothing. If the issue shows up, it stays like that for a while and then randomly disappears again. Only for it to randomly come back.

I'm pretty sure it isn't a thermal issue, it's a small CRT which doesn't use a lot of power and doesn't really get hot. The issue also appears and goes away randomly. And with the parts open on my bench it still happens. I've blasted the entire horizontal path with hot air in case of some cracked solder or something like that. But it still happens.

I suspect it's actually one of the other circuits that throws off the horizontal deflection. Probably something shorting or close to somewhere. The weird thing is, it doesn't collapse, it just loses horizontal adjustment. It's as if the pot is bad, but the pot is perfectly fine. I'll have to get out my notebook, print out the schematic and start drawing it out. That usually does the trick to get my brain to figure out what the actual issue is. Somehow even after using computers for so long, I need to revert back to how I learnt it in school back in the days to fully engage my brain. Computers probably are too easy and make me lazy.

Of course and we won't reuse them, that's not hygienic! A new bottle every time is the ticket!

Finding datasheets and service manuals is a nightmare. So many websites claiming to have the right file, only to end up being a scam and not having any files. Having files they have no right to and are publicly available behind a pay wall. Having weird online viewers instead of just giving the file. Padding the file with extra pages of nonsense so they can claim more pages and a larger file size. Having the wrong file mislabeled. Etc. It goes on and on. And then there's the sites that redirect a thousand times and then crash the browser. I hope I didn't just get a virus or something.

All I want is to fix this old CRT from 1981 so I can enjoy it for a few more years, is that too much to ask? And back in those days they actually cared about repairability. Especially the services manuals with scope traces for the test points save so much time troubleshooting.

Archive.org is a good place luckily. If it isn't down because shit heads can't behave on the internet. As a species we really like to get in our own way all of the time.

And no I still haven't fixed up that CRT. It is working now after replacing two weirdly behaving transistors, a new power cord and a new power button (old one worked but didn't stay on unless you held it on). Replaced a few caps but most tested fine, good quality caps. Even the once I replaced were working, but marginal on the ESR. Cosmetics are also good, but there is still an intermittent fault with it losing horizontal size adjustment. It goes from fine and perfectly working to a little too narrow without any adjustment. 90% of the time it's fine, 10% of the time it's faulty and it switches random. I've been going mad tracing where the issue is, but I will fix it one day.

On the one side we have a perfectly serviceable candidate, maybe not the best ever, but pretty damned good. On the other side we have a diaper wearing grandpa, with severe cognitive issues who is not running for president but instead to be king/dictator. This second candidate is rude, shits on everything, is a racist piece of shit and a felon to boot. He is running only for the grift and will fuck over anybody and everybody (except for his own daughter who he just wants to fuck).

AND SOMEHOW AMERICANS BE LIKE HOW CAN I EVER DECIDE 50/50

This simply cannot be reality

Sounds like a skill issue, fuck them kids

For me being impressed with SpaceX is kinda like loving a piece of art even though the creator turned out to be an asshole. Or liking Star Trek, even though Berman was shady af to put it mildly.

What SpaceX does is very impressive from a technical point of view. Even if the rocket never amounts to anything except this one successful test, it's still amazing they pulled it off. It tickles my engineer brain. And I think it's worth to honor all the people that made it happen, despite them having to work for Musk. Combine this with what could be in the future and you can hopefully see why people hail this test flight.

Now I still have serious doubts about Starship in the moon program. The on orbit refueling seems very sketchy and unproven at this point. Sure they will get two rockets into orbit, mate them up and transfer some fuel, that's a given at this point. But how much fuel are we talking? And how fast does the turnaround need to be to prevent losing a lot of it? How many ships and how many launches? Will this completely offset the cheaper launch costs due to reusability? It's a huge unknown and will push back the moon program to well into the 2030s.

After fans dug into the lore they found out through a series of item descriptions and beta data the Naked Homer Simpson character was in fact gay. When Hidetaka Miyazaki was confronted by interviewers if he could confirm Naked Homer Simpson was in fact gay, he just smiled and said the fans could find out by looking at the boss fight closely. It turned out if you removed a piece of level geometry a rainbow heart could be seen with the initials H and S below. Thus confirming for once and for all Naked Homer Simpson was in fact gay.

Or at least that's what I remember from the 3 hour VaatiVidya video about it.

As so often with anything related to maths, pi pops out at the most unexpected places.

It can't hurt to give it more cooling capacity. But it probably doesn't matter much. It will run a a bit warmer with the sticker, but still be well within what the hardware can handle. Since it normally isn't a performance critical component, it won't run too hot and cooling it more gives no benefit.

All the same, I kinda hate it when they put a big heatsink on something and then cover it up with stickers. But the size of the heatsink is usually part of the marketing and not an actual design requirement.

The Netherlands blames Russia for shooting down commercial flight MH17. (Rightly so) Almost 300 people died, mostly Dutch. So the Dutch giving their F16 planes including training etc. to Ukraine to shoot down Russian planes seems fitting.

Can someone do the math on this? What kind of force would you need on the blade to cut through 15 fat rich person necks? How heavy would it need to be? And what speed, like how high would the drop need to be? Would it be strong enough to just hold at two ends, or would the flex cause issues with it not dropping straight?

At this point it would probably be better to have some kind of pneumatic cylinder that chops off a single head, but does it really really fast. That way you can just drop down the rich asshole, lop off their head, pull the body away and plop down the next one. How much throughput could we get with that?

Not magnetic, but it can get statically charged and be attracted to stuff and even stick on the non stick side. However this is usually just a pain in the butt and not an intended feature.

They don't actually understand any of those things. They just think white skin, blue eyes and blond hair equals Uber mensch and thus the divine right to rule the world. And just like the Nazis, the fact that most of them don't actually conform to the qualifications they dream up is beyond them. That's why you see those pictures of Trump as a muscular Jesus, they are very detached from reality.

The electron shells are just a model, that's not how it really works. Look at this image for a more realistic model of how an atom works:

https://en.wikipedia.org/wiki/Atomic_orbital#/media/File:Hydrogen_Density_Plots.png

Based