Fixing a rescued amber CRT
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- čas přidán 8. 09. 2024
- For today's video, let's take a look at this adorable little amber gem of a monitor that was saved from being turned into scrap metal. Turned out it had a fault causing interference in the image, so, let me find the fault and fix the monitor!
-- Info
USI International
Model No. EV-9031A
USI Pi4
1 Park Lane, Brisbane, CA 94005
Taiwan Kolin Co. LTD.
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Sanyo Taiwan and Kolin seem to be neighbors or share the same building, both formed in 1963 so can't be a co-incidence
Very likely the same company, just that Sanyo was not adverse to doing contract manufacture for anybody who placed an order, simply using the same designs and parts, but with a different label and perhaps different colour plastic used in the moulds. To Sanyo no difference, just a job on the line, and they likely still made the same profit, as the other to them was just another distributor making a mark up.
@@SeanBZA yup, Sanyo OEMed LOTS of stuff to other companies.
That's a very neat little monitor. I love the little CCTV box style monitors from that time period. I'm not hugely fond of amber. I'd rather have white or green. But it's still cool!
I agree. I personally like amber displays for dumb terminals, word processors, etc.
Most of the high end terminals I used in my university days supported "Inverse" mode. This led to the term "Trogging" which referred to whenever you were pulling an especially long coding session, and your eyes were getting tired, you'd flip the inverse button and put on your sunglasses. It was usually enough to get you another few hours of coding time.
Sounds sick!
The B+ designation comes from the days of the original radios, which were tube sets powered from batteries. The A battery was for the cathode, which was also the filament as separate heaters had not yet been invented. The B battery powered the anode, and the C battery was for the grid bias. The capacitor tester didn't pick up the leakage because there can be a threshold voltage where the leakage starts and the tester uses a voltage that is below the threshold, while the set uses a voltage that is usually just above it. That's why adjusting your input voltage down made the interference go away.
Spoil sport, I was going to mention the origins of B+. LOL. (Although not in quite such detail. Nice one.)
What's your theory on why tapping it changed the leakage voltage?
@@djmips If the capacitor is dried out, due to the heat comming off the heatsink, then the leads inside could have enough room to vibrate at a high frequency. (like a tuning fork). Tapping it might stop or start the resonance.
Yep, that's where B+ came from.
en.wikipedia.org/wiki/Battery_(vacuum_tube)
In Solid State Circuits, it's often changed to V+ as there is no A or C source.
Yes, many caps are voltage sensitive, especially ceramics, but I'm willing to bet that Adrins bad cap there is drying out and the plates are starting to separate from the paper, thus making it "microphonic" or shock sensitive.
@@djmips Tapping a component will change the way it behaves as you are sending a vibration through the component. A noisy resistor can go silent again if you tap it. A capacitor will change if you tap it due to the vibration moving the layers inside, particularly if the cap has dried out a bit
It's CRT month!
Hey Ben, I just picked up a 4 or 5 inch flat Paperwhite CRT inside a video telephone which has 0 hours on it. Works fantastic. Would actually be great for your real PIP boy project. Similar to the projection style of early Sony watchman TV's. You want it? Give a PO box or whatever and I can ship it to you.
Well there's a name I unfortunately have not seen in a while (my fault) Off to binge your videos..
3rd person huh ben its a conspiracy
@Ben Heck Hacks Was just watching your video where your video for the Pacman clone led where you were referring to it being mini CRT month 🤓🤣
Can we make Octuber a month to celebrate CRTs?
CPT stands for Chunghwa Picture Tubes Ltd. Taiwanese company. They have a website (with the same logo as on the tube) and seem to be still in business making tablets and the likes.
Chunghwa also makes LCD panels too, I’ve worked on a few TVs and laptops that use their panels. It’s alright stuff
i got so many tvs and monitors with their tubes, never knew that
Funny how it's Taiwanese but the name "Chunghwa" (中華) literally means China.
@@signbear999 Taiwan is the Republic of China though?
They filled for bankruptcy in November 2022
That "older" connector is called a PL-259.Often used for antenna and older scopes.
The PL259 is the male plug that would go into that jack. The female on the back of the monitor is an SO239.
I came here to also say heavily used in amateur radio (that’s how I know it at least): en.wikipedia.org/wiki/UHF_connector
@@pb7379-j2k fun discovery last week when I found the CB-ish radios I'd ordered had "UHF" and the antennas are BNC.
@@RoamingAdhocrat it happens! There are adapters luckily
@@pb7379-j2k yep, the adaptors are here now, but it meant I couldn't test the radios with the antennas before I'd gone ahead with installing the radios
So looking forward to my next visit, and replacing a cigarette socket power plug with a piggyback fuseholder. No more tangle of wires across the cab!
Great fix... great amber monitor! When amber monitors arrived on the scene, those with green monitors were jealous... amber just looked so much nicer.
B+ dates back to the days of valve (tube) radios. They typically had two batteries (often called accumulators) - A and B... A would be low voltage but high current to power the heaters, and B would be the high voltage but low current for the tubes themselves. B+ just kind of stuck. It's common to see it used in audio amplifiers, B+ and B- to refer to the power rails used.
Love when you rescue these vintage items. That's a really cool little monitor. I spent several years programming on amber CRTs back in school in the 80's, so these really bring back the memories.
beautiful little monitor, very glad it was saved
From the antique radio forum:
"DC restoration affects the TV's ability to maintain correct black levels in scenes with high contrast. Better-quality black and white TVs like the DuMont RA-103 have a separate DC restoration circuit, but cheaper sets do not. In a TV without DC restoration, if you set the brightness and contrast for good black levels in bright scenes with high contrast, the overall picture may be too dark in darker scenes with high contrast."
Yes, it was what happened on the TV set in the previous video.
Soak the de-soldering braid with flux. Brings it right back around. Thanks for the video!
That also helps keep it from oxidizing in the package, and solder doesn't stick to copper oxides.
amber is hands-down the best monochrome color!
8:29 CPT is Chunghwa Picture Tubes Ltd., related to Tatung. They were still around producing LCDs and OLED screens for computer monitors and TVs til 2019, though only called Chunghwa. They occasionally still had this old CPT logo in their LCD datasheets as late as 2010. Unfortunately they had to lay off thousands of workers in 2018 and filed for bankruptcy in late 2019 :(
Nice job detecting that issue. That cap was a strange fault. You ended up with a great picture. Those amber crt's look like they'd be much easier on your eyes, long term, than the bright green ones.
Probably as he mentioned a bad joint which he surprisingly didn’t just reflow... especially since bumping it restored it. Shame he just recapped it. Following that recap crowed!
Those top mounted heat vents were great for keeping your burrito warm!
The housing and tube on the Sanyo is probably identical and made in Taiwan. Where Sanyo most like used there own driver board and requested slight changes to the back panel to accommodate their board. Made in Japan just means the final assembly happened in Japan. I worked at a company that product was 95 percent assembled in Japan but the casino request certain parts then our plate would say made in USA.
The conceal power switch is cool. At a place I used to work the security would occasionally call us to fix a dead display, which turned out to have it's power button bumped.
That's such a cute little monitor, and a satisfying debug! Would be easy enough to add a removable AC cable as well.
Another CRT saved, awesome!
The design of this is rather reminiscent of the larger (13-14" I think) Microvitec Cub monitors used with BBC Micros in schools (and had a dreadfully loud flyback whine!!!), a very industrial-looking metal-boxed "cube" monitor akin to this one, but the Cub lacked a front control panel as I believe it was all kept on the back, aside from the CRT itself, the only thing on the front was a red neon indicator lamp, not even a power switch... :)
it had the advantage that there were no controls on the front panel for bored kids to fiddle with :)
I thought it was a CUB at first. :)
i dont remember CUBs being that noisy????
"B+" is a holdover from the early days of radio, when radio sets were battery powered. the "A" battery powered the tube filaments, the "B" battery was the plate supply (basically the main power supply for the radio), and the "C" battery was used for providing grid bias. so, in the days of vacuum tubes, "B+" was synonymous with the main supply rail. the practice is still in limited use today, but has been mostly supplanted in the solid state era with "+Vcc".
The screw style input jack is an SO239 coaxial connector used extensively by radio communication equipment, much less for video today.
And the plug is a PL259
@@zero0ryn Yes, SO for SOcket and PL for PLug.
I did that sharpie thing with my belts when I was enlisted, I miss CRTs
That right B+ and B- that means battery which is indication for the anode supply of the tube.
A+ and A- were the filament (heater) supply. C+ and C- were the grid bias.
CUB monitors were used in all schools here in the UK, with Acorn BBC Micros. I have two and they are brilliant, just like this little guy you fixed.
Nice video thanks.
they made a green monochrome version of this with green lettering on the front -- I have one, but have always wanted the amber one so good find! These are very stylish looking monitors imo! Mine is slightly different with no 12V DC input or impedance selector.
I haven't read any of the other comments, so apologies if you've already read something similar. The bow on the edge of the picture is caused by what is known as pincushion. The scan rate needs to be slower at the top and bottom than it is in the middle of the picture, due to the fact that the picture tube is wider in the middle. On monochrome sets this is sometimes done with magnets on the scan yoke or sometimes it's done with a pincushion correction circuit. Look for a pot marked p/c or something like that around the line stage.
I would guess that the heat from that heat sink next to your bad capacitor caused the internal weld point for one of the two pins to break/crack partially. It's a good example of how much difference a top quality connection/part can make, even when frequencies are relatively low. (Well under 20MHz.) Also a good example of why NOT to place capacitors next to heat sinks!
Thanks for this video.
the regulator transistor likely doesnt 'shunt' current/voltage down but passes the supply voltage through it controlled by another transistor, the big resistor is likely shunted across it to give it some voltage on its output so it will start up, some regulator circuits need this
My thought was the resistor is so the transistor doesn't need to work as hard. Resistors are cheaper than transistors and they (usually) don't need heatsinks.
@@eDoc2020 partially that as well, but mainly that some regulator circuits need some voltage on their outputs before they can drive the pass transistor, they use the regulated output to feed the voltage reference stabilizer, so making it more stable, with no output, no reference, so no output!! Thorn here in the UK used that circuit design for at least one portable tv, the parallel resistor run quite hot in normal use and if the pass transistor went open circuit, the resistor would burn up quite quickly
My whole C64 experience as a kid was on an amber screen. Except for once, when my mum let me connect it to the tv. I was blown away.
The amber was used in security for preventing night blindness by light and keep a high enough contrast. The idea was the same as the red light on boats etc at night. It didn’t help much but, it helped sorta. It was better then the green. Easier to look at in the dark. And when needed respond and go in the dark and still be able to see with a dim flashlight.
The guards should have worn pirate eyepatches. Preserving night vision is almost certainly why pirates would use them when they had two good eyes.
You're supposed to use a chopstick to tap the board.
Yeah, B+ comes from the early vacuum tube radio days (and originally they did use large batteries). Found online: B+ (and B-) represented the high voltage circuit, A+ (and A-) were lower voltages for the tube filaments C+ (and C-) was the (also low) voltage used as the grid bias on the tube(s).
Those amber CRTs are beautiful. I had the opportunity to work with a few a bit in the 80s. Great find you have there!
Most of the lion kingdom's childhood was in amber. We briefly had a color TV, but in those days there wasn't an internet full of CRT repair vijeos, so once the flyback transformer died, it was chucked.
Reminds me of the CUB monitors which were most often paired with the BBC Micro, very square case.
Great video, TIP: careful small puffs of freeze spray will show up many problems with components even more than tapping. Tapping is free, freeze spray is not is the down side.
Cheap canned air can be used as freeze spray, just turn the can upside down.
@@paulstaf Watch out for the splash, since this will typically eject cold fluid at higher velocity than the real freeze spray will, because more gas is coming with it. I have a fingernail with a flat spot in it because I got hit with flying liquid "canned air" twenty years ago. It does work though.
What a nice monitor. It kind of reminds me of the Microvitec CUB monitors that were seen a lot with the BBC Micro. Those had a metal back as well. Those were black and white though.
most CUBs, if not all, were colour, certainly all the ones i've seen were, 'possible' they did a monochrome model, i dont know
A second ADB channel? Dang! Yes please!!
This reminds me of two tape recorders I got as part of an EBay order lately. One was an Emerson made in Taiwan, and the other is a Realistic made in Japan. Both looked very similar to each other despite being of different makes and provenance.
I actually had that monitor! Still have the Sanyo 9" monitor and Apple II from 1979 and they still work perfectly (well, after a bit of maintenance recently!).
Amber monitors are really beautiful
Love these videos!!! You can probably plastic-weld that knob back together with a strong solvent like acetone or modeler's glue. It's not glue, it actually melts the plastic pieces together and they are as good as new.
yep, acetone or MEK(methyl ethyl ketone) makes good welds
Drill a little hole and it will be super strong.
Adrian, about the DC-restauration. In its most simple form it's just a diode clamping circuit that sets the lowest part of the composite signal, the negative going syncs, to -0,3volts. A more complex form of video DC restauration triggers on the sync signal and uses only the blanking part of the signal to clamp to zero volts. The DC restauration is necessary because an AC-coupled signal via a capacitor will always center itself around 0 volts.
Ahh, so it adds a DC bias.
@@UberAlphaSirus Exactly!
I absolutely love that you use a pointer to show what you are working on!
In case anyone is interested the big screw type connector is called a PL 259. I only know this because my dad, bless him, used to be into Ham radio and this is what they used for their ariel setups.
I nearly dropped my phone in the bath from laughing - Adrain "There's an X-ray warning... Okay, no big deal..." @5:37
USI stood for Universal Security Instruments. Originally based in Owings Mills Maryland and later on in Annapolis. Obviously this they bought and had private labelled but back about when this monitor was made I was working as a placement counselor for Russian and Vietnamese refuges and many found there first jobs were working on building circuit boards for security systems. There used to be a wall similar looking monitors in the QA area where they ran tests on production. Later around 1985 they pretty much off shored all production. Imagine they may well have sold these with their systems to monitor the status of the system when in use. and perhaps to view cameras but I would guess those would have had the white tube rather than Amber.
There was an early PC clone company called Seequa in Annapolis, do you know if they are they related?
@@TheodoreWard I don't think so, but by the time they moved to Annapolis I really wasn't in touch with them any more. There were several early clone makes in Maryland I don't recall Seequa, but it was a long time back.
CPT stands for Chunghwa Picture Tubes(中華映像管，or華映), which is a company under the brand Tatung(which is still a SOE at the time) that specialized in manufacturing CRT tubes for Tatung and other companies(like Kolin or Teco or Albatron...etc). They switched to manufacturing flat panel displays using Mitsubishi technology starting from 1997. But as the story goes, the slow repurpose of CRT factories and lack of panel manufacturing resources compared to AU optronics and Innolux lead to a big mess. They filed bankruptcy on 2020.
As for the Sanyo/Kolin similarity, I'd guess Sanyo sold/licenced their design to Kolin and Kolin made customized version of it for different companies, because these two companies don't really share too much in common(kolin stood with Mitsubishi too)
"Chunghwa Picture Tubes" it gets knocked down, but it gets up again..
I have the exact same one I got with an apple ii+ and a recap solved a lot of the issues I was having with it. I also had to pop in a single 1n4007 for the rectifier ckt since it had been fried somehow or another (I think it was a dry cap that did it) and that fully fixed it since the vert wouldn’t lock on.
Good grief! I saw that screen shot of Music Construction Set and had a flashback. That was the first program i bought for a computer. My father had just bought the infamous Apple clone from Sears. That program was amazing. i remember sitting with a small keyboard tapping out tunes and painstakingly inputting one note at a time using the joystick.
A gorgeous little unit
I think the threaded connector is just called TNC; T is for thread, B is for bayonet.
I was going to say it's always good to see an amber or green screen, but call me a firefly; I like anything that glows. ;) But sometimes it's just nice to get away from color for a bit. If there's only one color, there's no chance of taste issues.
amber color is so pretty! much better than the green/white
The green & white phosphors are a lot more burn resistant than the amber one. Has to do with the chemical composition of the phosphor.
I still like the amber phosphor better, though. ;-)
I love those little monitors
Thanks for another wonderful Retro Video Adrian! - I noticed that the apple II you had a pic of at the end showing the Sanyo was a Bell & Howell branded one! How cool. I always perfered Amber or White Phosphor to green anyway :D
My first exposure to Windows was operating some lab equipment (gas-chromatographs) back in the early 90s that was controlled by Windows based proprietary software on small orange, monochromatic screens.
Haven't seen that since.
Yellowing plastic makes things look old in a bad way. Scuff marks in the paint are mileage. Totally different, and not to be concerned about. :) Since this doesn't have any plastic that could noticeably yellow other than the handle section, it's probably going to look good for a long time to come. I think the broken pull tab may call for a bit of epoxy, Sugru, or automotive Bondo to restore it. I suggest embedding some pins, or tiny screws, into the surviving plastic to give your fabrication something to hold on to. (Also, I just discovered hot glue comes in black, if that helps any.)
That's a good display size for CGA and similar, and the Apple. When both the hardware and I were newer, I could have been happy with an even smaller monitor, but now I would appreciate being able to sit further away. It's a bit tight for VGA, but it still works if you're willing to lean in. I've even seen 800x600 SVGA CRTs that size, but kinda had to wonder why they existed. That might work in mono (no shadow mask) but it was not very useful in color.
I used to watch TV on my amber composite monitor by using a broken VCR which still had a working tuner to demodulate the broadcasts, because it was pretty easy to find those being tossed out -- the tuners rarely failed, it was usually the tape mechanics that quit first. It wasn't great, but it was good enough for light duty and far better than not having a TV at all.
This is almost the same one I had when my family was having the Apple ][ computer. Congratulations that you fix it and have it as one of your great collections.
Fascinating. Appreciate the repair info and the comparison to Sanyo!
Cool explanation about connecting it to a car cigaret lighter socket..
Somehow my 10 year old self popped up saying "Cool, I can use this little screen in the dashboard of my crappy old car and make it look just like K.I.T.T" ;-)
Also: "Always suspect electrolytic capacitors that are close to heatsinks" should be "Always suspect capacitors." ;-)
Sunflower oil is good for removing price stickers glue and its equvalents. Just do not let the oil+glue mix congeal, for then you'd need to start over. No need to use much of it, too.
Maybe other veg oils would also work.
That said, what a treat, an amber CRT. )) I could never replicate that look/feel on LCDs, although fancy software emulators do exist.
i had one of those. good little monitor. sure miss it now
I had one of those USI amber screens bought mail-order and a Panasonic 9" green screen that was also advertised in the magazines of the day. Hooked it up to my VIC-20, TS 1000/ZX81 and other 8-bit toys. No RF signals for me. I think I see a 9" beyond on the counter at 30:34.
Nice editing, I really liked the pause voice over you did. Thanks for sharing this one with us.
Amber monitors are so cool
Adrian, drip a little flux on your solder-wick and it'll work even better.
@Adrian's Digital Basement ][ use a "pigmented ink" marker pen instead of the sharpie on your black plastics as they are a true black and traditional marker pens leave an indigo sheen.
Yes! Love this! The Apple II was often pictured in ads with the Sanyo VM-4509, which is verrrrrrry similar in appearance to this USI. Super cool. Love the amber too. (edit - hahaha I see you got there at the end...)
Cool that you were able to fix the geometry issue with magnets! I used to work for LG electronics making monitor tubes and one of my jobs was to set the geometry for test samples. We used to call the magnets "helpers" and it was quite a skill to fix convergence and purity on colour monitors! It involved a custom Japanese language MS-DOS laptop, which had a RS232 connected CRT analyser with a sensor that you'd put on the screen and read off the values. I also used to use a luggable MS-DOS PC from a Canadian company (can't remember their name) that would do the geometry with a big bulky camera unit. Ah, if only I could have brought those things home! Love the videos, keep up the good work!
Reminds me of the greenscreen monitor I got from a surplus place to use with my C128 in 80-column mode along with a composite adapter cable which came with the PaperClip 128 word processor.
Good job on the repair Adrian. I've have just finished repairing a pair of late 80's EGA monitors that were filled with those "Elite" branded caps. Not having the equipment to test them, I ended up just biting the bullet and recapping both fully, which solved all the issues I was having (Dark picture on one and flickering on the other). A lot of mine seemed to be leaking. I've seen enough of them for a lifetime, over 100 caps in each.
maybe a 'poor' brand?
I actually have a bigger (12 inch) monitor that looks identical to this one. It has all the same controls on the front, but only an AC power cord and a single RCA composite input on the back. Mine has a green-phosphor CRT.
Sometimes with bad connections, it can be useful to use a hairdryer to heat up parts of the board and icespray to cool down components.
For a good demonstration of what's actually happening with DC restoration on and off you might want to pull out the oscilloscope. Clip your x10 probe onto the cathode output and make sure the scope is set to DC coupling. You'll see the waveform stays in place with DCR enabled and moves around without it.
tip-negative 12V input…
I love this and I want one
I was lucky enough to snag one of those exact monitors off a charity listing on eBay for a song about 2 years ago. It did have some burn-in unfortunately, but not bad enough to be too distracting. I donated it along with an Apple ][ Plus to my university's Museum of Technology where the whole setup quickly became one of the most popular interactive display pieces. They even took that particular setup with them VCF East last year. Best part is, I get to see it everyday on my way into work, since the MoT interactive display is in the building that I work in. Don't worry, I have my own ][ Plus setup at home (as well as others) with a Monitor ///, so I can get my vintage fix whenever the urge strikes ;)
That old screw connector is called a PL259 connector. It was very common on CB radio antennas. First time I've seen it on a video jack.
[Aussie] Oi, I see you got yer pokin' stick.
A slightly odd monitor. The SO239 input connector (same as on a CB radio) was common in the early video days, however all but gone by the time computers started using video monitors, so it's strange to see something that has a rather early vintage with its SO239 connector, but amber for computer use.
I wonder if it came out of the factory with two SO239's as per the Sanyo, and a previous owner swapped one out for the RCA/cinch socket.
The 'B+' designation is a hangover from early battery powered valve radio's. The 'A' was for the filaments, say 3 to 6V, and the 'B' was the main power, with extra's like 'C' etc for biasing etc.
The SO239 aka UHF connector was used in the UK for professional video more than 50 years ago! The BNC was invented back in 1951!
Mentioning amber monitors always having burn-in reminds me of my mainframe days. Amber monitors were often used for System monitoring so often showed the same display on most of the screen for years on end.
The large connector is an SO-239. I've got two of these displays. One is amber, the other is white.
Glad you fixed it !
Using freez-it would help locate the problem too probably !
Reminds me of my first Zenith Vm-100 green monitor if I remember correctly.
This cube looks similar to one our company used with an otrona “desktop
‘ computer designed by a couple of HP engineers. I have both in my at; got the Otrona about 1980. I recall it was amber. Otrona was DOS 3 inch floppies; there were two.
4:31 SO-239 connector, common on radio equipment.
I love all of the random stuff that I learn from your videos and the comments. I'm a wee bit younger than most of your viewers. Wish I was born 15 or so years sooner
we couldn't watch videos and talk like this on the internet 15 years ago, same with music. You might fall in love with old music, but having streaming services of any music you want at any time... can't beat that!
@@squirlmy was more saying if I was 15 years older I would've been able to play with this stuff as it came out instead of playing catch up
18:22 those patterns in the middle look really cool, like cross contour lines on some kind of illusion drawing
HF noise/oscillation
Beauty CRT
I recently picked up a small CRT like this, a Samsung b/w unit!
It does not have any DC restoration function, you're constantly tweaking the brightness depending on what is shown on-screen. Connecting a Raspberry Pi to it in graphics mode for example, with a dark desktop background if I minimize a window that is mostly white, the entire display's brightness goes up causing the taskbar to become very bright, blurry and unreadable.
Unfortunately I think my little set is quite worn out, though the tube still gets bright it gets very blurry when you turn the brightness past 50%, so you have to use it on a fairly dim setting. The only adjustable control on the inside is focus, and it doesn't respond to it at all. Maybe with some love it can work better, but I'm getting the idea that this is just not a very good quality unit.
It's also got some clearly visible burn-in, the grid that separates the four camera streams is burnt into the display and you can see some text in each corner of the screen.
If you fiddle with the brightness and contrast, it can still make a very sharp image and I like to use it as an SSH terminal for my servers.
Yay!
A restoration!
My dad bought me that Music Construction Set software as a kid and to this today I was never able to ever run it because copy protection on the software wouldn't let it run. It was the genuine packaged software on a genuine IBM PC XT. To this day I've always suspected it was because we had a Hercules graphics card rather than a genuine CGA or EGA. But it's a mystery. Today you can get open source music composition software that's better in every way anyhow.
And just in anyone queries it, yes that software was released for IBM PC at the time even though it was also on platforms like the Apple II. It would boot but just die at the part where it would check its copy protection
I found one in a whareouse very similar to that one, only its more basic and its black and white
It is beautiful.
Wow excellent to use with cellp
That is a neat little monitor! Nice restoration and good work finding the cause of the waviness!
Regarding having those caps too close to the heat sink - could a new cap be mounted higher (i.e. keep the legs of the new caps longer), then bend them out of the way, so the main body of the cap is further away from the heat sink?
possibly, but i bet the new cap is 105c rated, the original may not be
I wish my local scrapyard took in crts..would love a chance to find a little thing like this
What you observe is the voltage regulator *oscillating* . It's obviously a bit more complicated than just "a resistor wasting the excess voltage", because you have a transistor in that circuit, tool, and you need amplification to maintain oscillation. The required amplification is provided by the resistor. It's typical for voltage regulators (integrated ones and of course also discrete circuits implementing the same topology) to *require* certain capacitance on input and output to prevent oscillation. It seems your cap hat a broken joint - not necessarily the joint between the connecting wires and the PCB, but possibly a joint inside the cap. If the cap was "missing", you were violating the capacitance requirement. This broken joint maybe was fixed just from applying the heat when desoldering the cap, which might explain why you couldn't reproduce the problem on the tester.
very possible, certain 3 terminal regulators can go unstable under certain capacitor loads or lack of them..