I would check the flyback diodes too, just to be sure, wouldn't want those coils to get fried. You can also elevate the resistors from the board with littile rounded kinks in them to get the heat away. You used to be able to buy resistors with that in them already. That carbon scoring should be removed too as it can become conductive. Easy to desolder because it's lead solder. Some chipquick or similar can make desoldering the stubborn stuff much easier and safer on the circuitboards. In the future you might want to buy caps rated for 105C that are around any heat creating components to make them more reliable.
Very nice repair well done! 6.8v sounds like the filament voltage maybe? Not sure if those resistors are supposed to be so toasty but in any case you can install them a bit more elevated (longer legs) to try to help with dissipation. Also I was told the charred section on the mobo can be conductive so it’s recommended to grind it off and patch it with epoxy or similar. Nice monitor!
@@Epictronics1 I have seen power supplies where holes were left for components. Not spark gaps but for resistors to 'float' in the holes. As toasty as this looks, maybe dremel a window where the charred material is, given the resistors would fit the space between the solder spots. :)
You may want to use four or more resistors, instead of just the two toasty ones. Ultimately you need 0.6 Ohms (two 1.2 Ohms in parallel, as original), so you can use four 2.4 Ohm resistors in parallel. Or use even more resistors. The point is to reduce the power each of them is dissipating, and to increase the surface for heat dissipation. Oh and you might want to check the voltage across the resistors, to see the Power they actually dissipate, so you can make an informed choice.
100%. I don't mind its size. I can drop my iron in it without even looking. Those Pine stands are braindead. Not even an inset in the clip? What good is that supposed to do anyone? That's damage and injury waiting to happen.
Just so you know, you can find packs of those black clips, and other clips you might find in vintage computers, for automotive. We use similar clips all the time inside the interiors of cars.
That was quite a lot of marginal parts! I'm glad that you managed to finally resurrect the CRT! I used to have an EGA CRT for my Commodore PC-20-III. EGA is cool and all (especially the 5154!), but in the early 90's they looked more like the poor man's VGA. How unthankful we were back when... I got an SE/30 that has been the same as your CRT, a new fault emerge after each that I fix something. The final problem was unexcepted, a solder joint that re-cracked after just a few hours of use. I think that I've worked out all the kinks on this machine - for now. I'd better sell it before something breaks on it.
Yeah, we could have got these 5154 for free at one point. Now it's one of my rarest collectibles lol. I'd say you're lucky, my SE/30 looks like Johns mid-week battery-bombed mac lol
Video starts at 12 minute mark :) As usual, the capacitors didn't prevent it from working, but resistors did. One once said, bad capacitors would make the device perform poorly, but bad (open) resistors would make it not work at all ;)
Those dark marks around the leaky orange Matsushita capacitors are not from heat. The fibers of the PCB substrate soaked up the electrolyte, and that caused discoloration. That's an unfortunate property of these cheap phenolic-impregnated paper PCBs.
Wobbly screen might have something to do with h/v sync sections so I would look there first. Another possibility is if there are any pots inside for adjusting things they could be dirty. Or it might be some more bad/open resistors somewhere.
FYI, if you have matching values, you can replace Tantalums with Ceramics... thereby removing the risks involved in the highly entertaining failure mode of Tantalums.
Any idea if this is true in audio applications? I have a classic synth called and ARP Omni that is full of low quality tantalums. If I could replace them with ceramics I'd be much happier than if I replaced them with more tantalums. I replaced the electrolytics with polymer caps in the non-high voltage circuits already, in the hope of not having to deal with corrosion from leaking electrolyte in future.
@@chriswareham : I'm really not sure, but from what I remember Tantalums are used for their stability (they keep their capacitance) and because they can pack a lot in a small package. Ceramics on the other hand have a higher self resance requency and lower ESR and are safer and non-polar. On the minus side, I believe they can introduce noise, as they have piezoelectric properties (though moern MLCCs less so).
There seemed to be a lot of some white stuff on some of those boards. I don't know what it is, but it might be a good idea to clean it off, to eliminate the chance of currents leaking around the board. And yeah, those resistors looked bad right away, and should be replaced with some new higher wattage parts. A bit of air around them might be a good thing too.
Hi, back in the day after changing a few CGA cards to eliminate snow, i ended up purchasing a used EGA monitor and trident card. That combo lasted me 5 to 7 years untill the inevitable upgrade to VGA - Wolf3d You should be able to easily find commander keen EGA screen shots and EGA Trek - not to many colours are used but the crisp legible screen and graphics will be a guide Unfortunately there is not to many EGA graphics / images ( i keep thinking of the cat / baboon / King Tut images for Amiga 500 that people are familiar with )
Did I not tell you some videos ago that those golden ROe caps are crappy 😂😂😂 I know many people who don't believe it and all of them learn it the hard way. The should not be on any board. The brand is ROE (for roedensteiner, a W Germany company, now defunct and bought up by another company). Some are also marked "ero" and I guess "frako" is the same or very similar bad caps. Also from Germany.
I've seen that brand of orange electrolytics in German A2000 power supplies, they can have a short failure mode, and cook off, especially on the main power rails 🙂 That may be the reason those two resistors burned?
I've just been using the KU tip on my Christmas tree/writing implement -based soldering iron for everything. The only time I've had issues was for SMD components that were very close to other components, since the tip is quite wide. For the stand I'm just using the one from my old Hakko FX-888D, which doesn't work great (although better than those cheap plastic stands), so I'd be very interested if you find a good solution.
The picture's back, but it seems very wrong to me still that components are getting to temperatures hot enough to darken and char the board. Something's still not right
The brown color should definitely be yellow on a real IBM EGA card so your AST clone ega card must be set to use a IBM 5153 (cga) monitor instead for yellow.
That would also explain the instabilities with the real card. CGA runs at 15kHz but native EGA is around 22kHz. I'd suspect there are two horizontal hold controls on the monitor.
In your last PCjr vid you mentioned you had an idea to try out for higher stable cpu clock speeds and had ordered parts. Is a video on that still pending or did the idea not work out?
Yes, I finally got the part and actually started recording that video this week! Unfortunately, the PCjr is dead :/ I need to do some research and make a repair too
I have never seen any small stand better than these ones what you are looking for is a normal size stand. Or design one yourself, you can see with old tony
