I ruined this Amdek 300A after fixing it

[@adriansdigitalbasement2]

Thanks to viewer Todd, he pointed me to the SAMS schematic for the monitor, and indeed, that diode is just a bog standard 1N4138 part! I wasn't using my head there. Luckily, the 33v will just act as a normal diode in the circuit in this case since the voltages are under 33v. See Diode D101 on the schematic here: archive.org/details/cmt-3-2/page/n1/mode/1up

[@dr_jaymz]

You said you had another amdek300 so I was confused why you couldn't look at that one or connect it to the crt.

[@JoeCdaYT]

I was going to recommend that site when I did a quick search, good thing I looked in the comments. Too bad the monitor did not work out 100%. At least you got a good chassis to pit a decent tube into.

[@adriansdigitalbasement2]

@@dr_jaymz Heh yeah that one is away in storage at the moment -- sometimes stuff is really hard to get to :-)

[@adriansdigitalbasement2]

@@JoeCdaYT Yep exactly, CRTs wear out, it's just a fact. The other one has a pretty good CRT, so I'll swap the CRT and keep the electronics in case a hard to replace part on the one I keep dies, like the flyback.

[@michaelterrell]

@@adriansdigitalbasement2 I might be able to come up with a green 12" CRT for you. Do you have the tube number?

[@robinbrowne5419]

Seeing that dim amber monitor reminds me of when I was working in an office back in the 80s and the secretary was complaining to the boss that her monitor was too dim. "Look" she was saying "I can hardly see the bold." After fiddling with the knobs for a few minutes the boss finally said "Ok. Order yourself a new monitor." Everybody else chimed in "My monitor is dim too." "And mine too." Supressing a look of exasperation, the boss said "Ok Ok. It's Christmas time. Order yourselves new monitors for Christmas. Get colour ones if you want. But make sure you run it by me before you order them." So we all gathered in the lunch room to choose our new monitors from a catalogue. Upon reviewing our order the boss said "No. You can't get those colour ones. They are way too expensive." Then, pointing at the catalogue, he said "I meant you can get colour green, amber or black and white." :-)

[@FarnhamJ07]

After working in a repair shop for a good long while back in the day, I really have to recommend not rejuvenating CRTs unless they're already truly unusable. It was just never intended to be anything more than a short-term temporary fix: the point was to get you through a couple weeks at most, until a new tube could be ordered and installed. Couldn't keep every CRT in stock, let alone cart all of them around in the van! Nowadays it's a not the best idea unless it's already pretty much dead; even when it 'works', it accelerates further degradation by literally vaporizing the emissive coatings.

[@LaserFur]

We saved some CRT boosters from old sets to use. we would tell the customer that they have months to plan for a new TV. Note: the CRT boosters were different from rejuvinators in that they just increased the filament voltage.

[@adriansdigitalbasement2]

Indeed -- I wouldn't ever do it on a CRT that's in decent shape, but this one was pretty dim and blooming. It's really hard to show in the camera because the HDR recording and automatic exposure compensation makes it look better than it is. (Plus my basement is pretty dark.) I was 99% sure it wouldn't turn out better anyway with a high likelihood of being worse. Perhaps some CRT testers do a better job but this B&K 490B is simply terrible at it! LOL!

[@cheapasstech]

You probably need a beltron- yet again those are for the 1960’s sets

[@snagrul]

What would it take to actually improve a CRT that has reached an almost unusable state? Is it possible to somehow take apart the tube and reapply emissive coatings inside (or otherwise fix things), re-vacuumize and seal it up again?

[@cheapasstech]

@@snagrul would require some specialist equipment which is no longer made … making a CRT is sadly a one off thing like an incandescent lightbulb

[@vwestlife]

Step away from the rejuvenation button, sir.

[@mrnmrn1]

No, I use the same tester with good rejuvenation results. The trick is you shouldn't allow it to go through the three automatic cycles. You should turn it off right after the spark show. Also the timing seems to be off on this tester, it feels like the cycles are too long. The timing is done by 555s and the longer timings use electrolytic caps, which are if leaky, can make the timing longer.

[@martinda7446]

@@mrnmrn1 I watched and thought NO! this was a do or die tester. Mike Tyson of testers

[@mrnmrn1]

@@martinda7446 Yes, it's do or die, with at least 70% chance to die if you let it go though it's automatic 3 passes. But if you use it with caution, and turn it off right after the sparking stopped, it gives you at least 70% chance that the tube will be better than before, and 90% chance that at least it won't be worse than it was. I even had a good success rate with a real brute-force 'Mike Tyson' rejunetaion method, before I had this tester: 9V transformer on the heaters, 230V mains across the cathode and G1 with a 1N4007 and a 60W bulb in series (40W bulb for smaller tubes). It woke up much more tubes than it killed, usually they lasted a few months or just a few weeks, but sometimes years.

[@juliedunken1150]

how DARE A GAY COMMENT in Adrians videos

[@SgFireAlarms]

​@@juliedunken1150what are you waffling about, discrimination isn't cool

[@cjh0751]

This is exactly why i love you longer videos Adrian. Your just tenacious and won't give up and we learn so much from watching you. Great video.

[@tiporari]

Maybe in the future show a CRT you think is fine next to the "dim" one so we can tell. They always look fine to us on camera.

[@adriansdigitalbasement2]

Yeah it's really tough to show on camera -- so a comparison is not a bad idea!

[@ingmarm8858]

Yeah this one looked pretty usable for a non-grayscale application as was typical for these beasts.

[@treminaorugx]

Wake-up period for a CRT can be tens of hours especially if it has cathode poisoning. Best to fully let it wake up before attempting rejuvination.

[@rabidbigdog]

Working with pure-amber or -green displays day-after-day was actually pretty easy on the eye compared to the colour displays that followed.

[@mrnmrn1]

I have the same CRT tester. You should check the timing components in its rejuv circuit. It's using 555 timers, and I think electrolytics for the timing. So I would say, not just test, replace all the elctrolytics in the timing circuits. It might just apply the rejuvenating current for too long because of a leaky timing cap. Based on my memory from last year, when I was using mine last time, I felt the cycles of yours are too long. Mine is working OK, BUT there's a trick: it goes through 3 cycles of rejuvenation every time you start the rejuventation process. If the first pass gives a nice sparky light show like this one did, I would turn off the tester right after the sparks disappear, and test the emissions. Especially with small CRTs like this. Probably the first pass was successfull, and the two remaining passes ruined the CRT. The bright orange glow after the sparks was the cathode, that was overheated by the 25mA of current the tester was pulling through it. You should have stopped within a second at that point to save the cathode. I have great luck with this rejuvenator saving tired CRTs, since I usually don't let it go through the three automatic cycles.

[@tarzankom]

After nearly 40 years, it's tired and used up. Being in my 40s myself, I find that totally relatable. lol

[@bulwinkle]

Tarzan, you're just a kid. I'm into my 8th decade.

[@bent-jl6rc]

How are you feeling now ? 2 years younger? 😂

[@kilwala2242]

The brown gunk is likely an ethylene vinyl acetate (EVA) based glue gun adhesive that degraded and produced acetic acid (vinegar) as it decomposed.

[@semifavorableuncircle6952]

Usually some kind of chlorinated rubber based stuff. Guess what it breaks down into... Its really, really cheap and still used unfortunately because of that.

[@erickvond6825]

Something you might consider for future tubes is an inductive getter firing tool. It pulls impurities out of the gas from the tube. This is especially effective if a tube is slightly gassy. Of course of it's leaky it might work for a short time. The sure fire way to tell if a tube needs it is a discoloration of the silver patch that coats a small portion of the inside of the tube. If it's white the tube is usually gassed out. Other colors have other meanings but I'm sure you can look that up. The alternative is that I write the whole manual in the comments and while I'm sure a few people would like that, I don't think you really want a comment that long. Cheers for the great content mate.

[@SenileOtaku]

This was my first monitor for my Tandy 1000A (I had bought the whole setup used). I eventually ended up slicing the mesh off with a razor blade. Later on I acquired a Tandy CGA monitor to replace it. All of that has been gone for almost 30 years now.

[@enoz.j3506]

As you say ,that brown goop goes conductive over time,also corrodes tracks and components.This goop was used on many,many electronic parts.As a retired engineer what we used to do in the 80's with soft tubes ( bad focus etc), was to increece the filiment voltage,this improoved the electron flow to the screen,you dont need much increece,millivolts infact,now obviously the filiment would have a reduced life,but we never had any come back with failure,many a 20"plus tube was done this way,and the results were positive.This wasnt an option on some tubes, just depends on the filiment voltage circuit,many were just a resistor reduction Good channel,Thank you Adrian.

[@kissingfrogs]

watched it twice. Awesome tutorial on crt. Thank you so much for sharing. I have tinkered with these but you have well demystified so much for me

[@gallgreg]

Awesome troubleshooting! Sad that you didn't end up getting a good monitor out of it, but an excellent educational video anyway!

[@TBMartin]

I know you said in the video that we have probably seen this Amdek 300A before but honestly its the first time I have ever seen one and i was born in 1979 (UK). Great video as always and thank you.

[@Shmbler]

That same brown gunk was still used in a 24" LCD monitor built around ~2012. It totally corroded several components on its LED driver board.

[@russellhltn1396]

The idea behind amber monitors was supposedly less eye strain. However the amber phosphor wasn't as efficient, so the drive had to be increased. That accelerated burn-in and shorted tube life. Call me old fashioned, but I like green screens better. I found the amber tended to be a bit fuzzy.

[@BG101UK]

I tend to agree on that. My eyes certainly respond better in terms of visual acuity with the shorter green and blue wavelengths. Have you ever tried to read stuff under low pressure sodium (SOX) lighting and also (separately) clear mercury vapour? You'll likely see what I mean if you have.

[@KenjiUmino]

[@BG101UK]

@@KenjiUmino Same here regarding appearance but since our eyes are less sensitive to those wavelengths it would mean driving the CRT much harder. I think cyan would work well in both respects though.

[@TheSimTetuChannel]

Great Scott! After all this time I finally realized your EEV Blog multimeter is the 1.21 GigaWatts model!

[@valliantsteed]

I did learn TV repair in the late 1990/ early 2000s. The way we did it with a similar König Tool was never use the auto rejuvination, give it short burst with the manual trigger and knock the crt's neck near the heating filament with the back of a screw driver (not to hard of course)

[@aziztcf]

I'm liking this idea. Guess the auto rejuv doesn't take it into account that it's working with decades old tubes!

[@laserhawk64]

Tonight on Adrian's Digital Basement... Adrian learns the true meaning of the phrase "the perfect is the enemy of the good" -- and that he very likely has no shared heritage, after all, with Victor Frankenstein. Alternate title: "How to snatch defeat from the jaws of victory".

[@minty_Joe]

"Quiet, dignity and grace..." ~ I-gore (Young Frankenstein)

[@randyab9go188]

I have a Sencore 7000 and it is the absolute best at rejuvenation. It goes all the way from a gentle cleaning up to a full rejuvenation. I have had dead emission tubes restored to a very useable state and weak to like new and it held. If you can find one working for a reasonable price get it. p.s. the Sencore has a setting to draw 1 ma as a very light restore. Works wonders.

[@titactaco]

At about 38:50 you said "That looks like it's actually a zener diode, that's problematic" -- and I was just very curious about the 'why' - I know you can't explain literally everything in every episode, but I'd be curious to understand. Thanks!

[@adriansdigitalbasement2]

Zener diodes start to conduct at a particular voltage. That voltage can vary from a couple volts to 50, 60 or more. So you have to replace a zener diode with one of the same voltage usually -- but unless you know what that voltage is, you are going to have to guess or reverse engineer the design to figure out what the working voltage is.

[@graealex]

@@adriansdigitalbasement2 Technically, all diodes start to conduct at a particular (reverse) voltage.

[@aziztcf]

@@adriansdigitalbasement2 Not to mention the zener voltage, meaning it's not just the diode voltage which lets it pass current one way you have to worry about but the zeners have another voltage that cause them to let it pass the other way too.

[@tigheklory]

I have a Heathkit rejuvenator and it works great. I always do a clean before doing a rejuvenation. Usually a clean will do the job.

[@jabbawok944]

I just repaired my set of active speakers, where the fault was a bad zener. It got hot and eventually went short. It was part of a circuit that split 24V in to +12V 0V and -12V.

[@stephenoflaherty5656]

Brown gunk ate away inductor leg on quite recent LCD TV. Didn't have replacement so unwound inductor to extent leg so could solder back in🤔. Worked 👍

[@mashrien]

You should've run it through the 50mv cycle as well, if it was already a lost cause then the only way to go is up.

[@paveljelinek772]

Do not worry about zener voltage.. no matter at all because it is reverse voltage, meaning if reverse voltage goes higher than it's rate, POP! If lower, good, it has to be lower

[@video99couk]

My home-built CRT reactivator has never destroyed a tube, though I always quoted a 10% failure rate to people just so they were prepared for the worst. It's a slightly improved version of a design published in "Television" magazine in the 1980s. It looks like your Konig one may have a fault.

[@mrnmrn1]

Yes, the cycles seem to be too long. I have the same tester, I use it for rejuvenation with good results. The main problem with it is the three automatic cycles. If it sparks like crazy at the first pass, it should be switched off, otherwise it kills the cathode during the next two passes. Probably that's exactly what happened here. After the light show, the CRT was happy, but it got ruined by the remaining two and a half cycles.

[@pawspaws101]

Worked as Electronics Tech back in the day, and the CRT Tube Rejuvenation was over in the factory. Not sure why I didn't go over there more to see what they did. But it all look like Voodo Magic to me back then! I stuck to TTL and Digital from that time on! Glad I did!

[@horusfalcon]

Yeah... "brown gunk" was, in some cases, applied at the factory, and was used because it was expected to exceed the service lifetime of the equipment. Later equipment used either low acid RTV, epoxy, or something like Glyptal to dope down components. I'm wondering if the brown stuff is a form of hide glue? I've never seen any CRT rejuvenators that actually worked for more than a few weeks. I'm confirmed in the opinion that "rejuvenation" might be nice for a little while, but leads finally to equipment failure. I would love to see a "new" (or at least "newer") CRT put in this old classic.

[@RealZomBiE8192]

I've been working with CRT's sice 90's and my teacher told me that every time CRT sparks, it's 80% of its life gone away.

[@Potts1966]

Nice video, enjoyed the process of trouble shooting, even if the outcome wasn't what you wanted.

[@dennissmithjr.5370]

RIP Amdek 300A, you lived a long life and are now ready for a long rest.

[@ceasecommed]

Used to hook vcrs to composite monitors back in the 80s in middle school

[@HiFiasco]

That zener diode is part of a video level regulator circuit which is basically setting the shelf of the video signal so that adjustment of the contrast control or varying cathode load don't affect the picture.

[@donmoore7785]

Interesting theory, but as explained in a note above, it turns out that it isn't a zener.

[@HiFiasco]

@@donmoore7785 it wouldn’t have to be, necessarily. The diode appears to be part of a DC restoration circuit, so a zener would serve as sort of a gilded component where a general purpose component would do.

[@RudysRetroIntel]

Thanks for sharing and showing the other hand is not near the monitor when on and troubleshooting. Love your monitor repair videos and the other too.

[@floooogy]

Did you discharge the Kathode in 6:20 with that measurement of the high voltage? I may triy also to repair a CRT,but I 'm a beginner and afraid of the high voltage.

[@Nabraska49]

That was awesome that you could find that one little component that stopped the whole show and yeah after watching your rejuvenation doo hicky thing bust up all your tubes .. I get nervous every time you bust it out ..

[@tenminutetokyo2643]

The Sanyo cube monitors were all the rage for Apple II back in the day. The tiny security type monitors.

[@8-bitbitsa821]

Schematics and a Sam’s Service Manual is available for this monitor, no problem. I was excited to see at first as I thought you were doing the 310 version(I have a faulty one here). For the other Amdek 310 monitor version (with the 9pin input) nothing I can find ! The boards are completely different for the 300 and 310 models, sadly 🤷🏻‍♂️

[@danielk2112]

With those Konig rejuvenators only 1-2 seconds of needle deflection on rejuvenate on a mono CRT then turn it off else you will strip the gun bare

[@ThomasTalbotMD]

I used to have an Amdek 300A as a secondary monitor - amber. Nice details, terrible grayscale contrast

[@FabioJulioRoque]

I never saw the sparks in the rejuvenation process before, even in the specialized videos. Nice shot as a picture. Thanks for sharing (in spite of the process killed the remaining life of the tube 🥲)

[@evensgrey]

Always seems to be the blood diodes in these old monitors. You're lucky you've got any readable markings on it. The 8-Bit Guy fixed some monitors that had been stored outdoors for a few decades a while back (fortunately this was in Dallas, TX, so they didn't spend all that time wet) and his monitors didn't work properly because each had a critical diode that had disintegrated and was completely unreadable before it fell apart.

[@shmehfleh3115]

This is some good info. I have a Commodore 1084S that has a short somewhere in it. I'm gonna look for the gunk and work backwards from there.

[@markitzero12]

As someone mention is that rejuvenating is Temporary and from what I learned from shango066 that there are some monitors you can't do rejuvenation on like for example Sony Trinitrons because it will just grenade it.

[@garthhowe297]

I really like all of your videos, but this one was exceptional. I have a number of CRT monitors, so I am very interesting in following your troubleshooting. Great video. I'm curious, are you able to lock your camera exposure to the normal room lighting, and then show the CRT you are working on?

[@maxheadrom3088]

SIr, that yellow stick is too short. I remember my dad showing us high voltage sparks by just getting a long screwdriver near it. It was an old tube Philips very large (for the time) and faulty TV but, well, high voltage is a killer beast. Thanks for the troubleshooting! I have two color Apple IIgs monitors and one is not working while the other has issues and your troubleshooting will be helpful! I got info from a guy called Mr.Joooooohny (nor sure how many letters - really nice channel that I'm not sure still exists) who told me "if the filament is lighting, your tube is ok or fixable". Very nice guy from Eastern Europe, btw!

[@dosdoktor]

The problem is that you welded the filament to the cathode's case. This kind of tube wants to be held top-down while rejuvenating so the filament can hang free.

[@EngineeringVignettes]

I got the inside scoop that you are going to be a special guest star this Friday on a show hosted by a guy with a very special history. :D Looking forward to watching that! I hope it goes well. Cheers,

[@wesley00042]

My dad had this monitor for use with the 80 column mode on his Atari 130XE

[@dannye5335]

Excellent video I'm glad you decided to cover this especially because not many people are using crts anymore. I have a small monochrome crt from a cnc machine that has no high voltage. It kept burning the hot and one of the resistors in that circuit. Any advice where to start looking for the problem?

[@jimsteele9261]

I had an Amdek Color 300 on my Atari 800. It replaced the surplus Magnavox monitor I pulled out of a scrapped terminal.

[@markdjdeenix6846]

Gutted 😞hopefully you will get another tube come your way

[@BG101UK]

I don't know if you watch shango066's videos but he does say that rejuvination attempts are usually a waste of effort on really worn-out CRTs and even if it does work, it usually doesn't for long. It might work on CRTs which have just "gone to sleep" after a long period of storage, I think.

[@michaelterrell]

The CRTs last longer when powered by AC. A school system bought about 100 Channel Master TVs that had series filaments. Within two years, the CRTS all started to fail. The so called engineer had a total of 85 volts in the series string, so he used a 'Diode Dropper' to only apply one half of each cycle to the filaments, cutting their dissipation in half. (120 VAC x .707 = 84.84 effective voltage) I added filament transformers and let them burn in for a few hours with a CRT brighter, then removed the brighter., then returned them to the schools. This effect is known as Cathode poisoning..You can have the same effect from keeping the filaments hot, with no B+ for a long time. I changed my first CRT in the mid '60s at 13, and I was a Broadcast Engineer less than 10 years later. Most younger techs haven't worked enough with tubes to understand them properly.

[@eDoc2020]

@@michaelterrell I'm not saying it isn't true but I don't see how running the filament on AC vs DC would have any effect on the cathode emissions. On normal CRTs the two are electrically isolated. It might have an effect on directly heated cathodes like transmitter tubes though.

[@michaelterrell]

@@eDoc2020 Believe what you want. I've seen it first hand in hundreds of poorly designed TVs. Many monitors use a winding on the flyback to power the CRT, instead of readily available 12VDC.

[@BG101UK]

@@michaelterrell "Most younger techs haven't worked enough with tubes to understand them properly." Unfortunately this is also true of me, All my formal "education" was about solid state stuff and so was my time in the TV service trade; my only experience with valves (tubes) is with my hobby at home restoring and using vintage tellies.

[@michaelterrell]

@@BG101UK It was definitely a different mindset. Tube circuits were simple, compared to today's electronics. Early radios used 50% tolerance resistors, and 20% tolerance on wound paper capacitors. Resistors were made, then test before having the color bands hand painted on them. I often hear complaints, 'Every resistor was out of tolerance' from people who insist that 20% was the lowest grade ever produced.. They were the E3 class, and we are up to E192 for some resistors. Gain in tubes varied quite a bit, as well. The old Radiotron handbooks were an in depth reference on early electronics. The third and fourth editions are available online as free scans. ere is a detailed description of the various resistor E series: en.wikipedia.org/wiki/E_series_of_preferred_numbers

[@terryraymond7984]

Hey this is very interesting Adrian you really know youre stuff with monitors

[@StevenSmyth]

Amdek 300 is the first thing listed on a SAMS search. So schematic and parts list at least.

[@tony359]

Nice video, I enjoyed the troubleshooting journey! Looking at the title I was expecting a short or some sort of some physical damage but no, fireworks ruined it! :) (Nice to watch though!)

[@gordonwelcher9598]

The rejuvination cycle ran for too long. I used to zap them for a second or two on manual cycle. The flash was all the cathode material burning away. Next time just give it a bit on manual cycle.

[@dennisp.2147]

My experience with that line of monitors, back when they were new, was that they had terrible burn-in and low brightness/bloom after just a couple of years. Amdeks had a bad reputation for that.

[@martinda7446]

Re rejuvenation. Some are saying it's only temporary etc. Yes the idea was get some more life before replacement. But, the facts are this is a poorly understood science.Results will be variable is about all you can say. I've rejuvenated some tubes that continued to give superb results for years after and others that simply do not respond at all. That is a big range and the only useful thing that you can get from it is try and see. Some tubes are well known for being tricky and unsuitable for regen, but as I say try and see. Fingers crossed.

[@tw11tube]

I noticed that when you turn up the brightness, the picture blooms and gets bigger around the same time. It's well-known that the increase of picture size is caused by the anode supply being overloaded, so HV goes down, the electrons get slower and spend more time near the yoke getting deflected. The other grid voltages are generated on the same transformer, so if HV breaks down due to overload, so does the focus voltage. So possibly the blooming is not an effect of the CRT being overdriven itself, but "just" of the supply being overloaded.

[@eDoc2020]

There are two things sometimes called blooming. The first is the picture enlarging when turned up due to the HV falling. This is unrelated to the tube wearing out and in fact tells you that the cathode is strong enough to pull a decent amount of current. The other thing called blooming is the beam "losing focus" when bright. This is usually the cathode being worn out and needing to use more emissive material.

[@gotj]

That's a really beautiful monitor.

[@david4368]

If it isn't broken, fix it until it is. That's the way it goes sometimes.

[@Darxide23]

Steve? Is that you?

[@eeveegamig]

I have a Nintendo wii from 2009 that sometimes crashes during games. Boy I loved that thing.

[@retropuffer2986]

I didn't have an Amdek but you saw these monitors everywhere!

[@Kboyer36]

Sadly finding ones in good shape is getting really hard. You don't often see completely dead ones like this but they usually have really bad burn in on the phosphor. Seems to be a common problem with a lot of Amber CRT's.

[@osgeld]

dunno if I commented this in your other video's but whenever I saw one of the screens with a mesh glare filter they always seem to have a "pantyhosse run" like down the middle, guess it makes since since the fashion of the day was big hair, shoulder pads and wolverine nails

[@kaitlyn__L]

“Wolverine nails”, that’s hilarious. (And I say that as someone with just such nails….. no falsies here!)

[@NEEC1]

I believe the camera showing the CRT as brighter than it is, is because of the reduced dynamic range of the camera, being less than the human eye. Dim things look brighter basically.. You'd have to be shooting in S-log or something to get a real representation of the dynamic range. Probably not worth it!. Seems like the 'rejuvenation' process is really hit and miss. More miss than hit!.

[@NEEC1]

PS. sometimes using a small rubber hammer or end of screwdriver lightly tapping the neck can help. Just enough to shake up the gun.

[@NEEC1]

PS number 2.. I once saw a technician take off the anode cap and with the CRT base disconnected, run the anode cap around the CRT pins. Causing some sparking.. It worked!. Picture got better. I've never tried this personally but thats what he did.

[@MyCrazyGarage]

I think that crt tester is broken, the rejuvenation feels waaaay to long compared to others (less than 3 seconds).

[@adriansdigitalbasement2]

It's the BK Precision 490B and reading the manual, it is working "As designed." It's using 555 timers to run the process supposedly automatically .... I had an old B&K from the 60s (a 460 I think) and it was 100% manual but also almost always made CRTs worse in the same way.

[@MyCrazyGarage]

@@adriansdigitalbasement2 Oh interesting, didnt realize that it is a "smart" one. Just thought the internal timer broke and went from 2 seconds to 30 seconds non-stop rejuvination.

[@kaitlyn__L]

@@MyCrazyGarage it’s a pretty fascinating microcontrolled (IIRC) unit from the early 90s! I’d definitely recommend checking out Adrian’s video from about a year ago when he got it (though alas I don’t recall if the title specifically calls-out the new tester, or if he simply circumstantially shows the new unit in one of the CRT videos).

[@graealex]

@@kaitlyn__L Yes, it takes its sweet time and uses advanced micro-electronics to fuck up CRTs, instead of doing so in only a few seconds.

[@aziztcf]

Could the diode be there for back emf? Now I'm wondering if the 30 odd ohms I see on my laptop mb could be a failed diode instead of a cap. Hmmh, gotta build that kelvin probe for my DE5K

[@user-fr3hy9uh6y]

Back in the 70's you could get a CRT referbished (used it for color tv repair). They would cut off the neck and replace it with a new one. I'm guessing that that type of service is not around anymore. Who has a CRT anymore but with the retro movement?

[@michaelterrell]

The last known rebuilder went out of business a decade ago. What little supplies were left were for early color TV CRTS A TV museum has the equipment, but no source for new guns. I have some good, used green CRTS., but I gave away the only Amber ones years ago. I have about 100 old monitors in storage, along with some Telex color IBM mainframe terminals. I am donating most of my collection of Mini/Mainframe hardware to a museum in PA. I do have dozens of working 360KB floppy drives, and a bunch of Commodore drives.

[@randyab9go188]

Look at how the UV yellowed the cabinet. The video input panel shows the original original color on the edges.

[@adriansdigitalbasement2]

Yeah it definitely needs some treatment -- although I worry the painted front bezel might not appreciate it.....

[@brianwild4640]

When I was learning Tv repair I made my own tube rejuvenator we never did it for as long as you did it would be 5 seconds max the heater voltages and screen voltages are way higher than normal all the testers I used that were commercial you held the button for a few seconds

[@EyeOfAllah]

Do you ever use decontamination methods after working on Cathode Tube Monitors?

[@kencreten7308]

This was really fun. Thanks!

[@BulletproofKuloodporny]

Congrats u first

[@kencreten7308]

@@BulletproofKuloodporny I was? Wow. Thanks for letting me know. Heh. I'm not usually first.

[@BulletproofKuloodporny]

@@kencreten7308 I'm also not usually first. If you want to know who is first click the settings like button in the comments section and click sort by newest.

[@kencreten7308]

@@BulletproofKuloodporny OK. Thanks for the pointer.

[@twocvbloke]

As for CRT rejuvination, it's possible the newer tool may have faults of its' own, causing it to over-do the process of "rejuvination" ending up with it wrecking the guns rather than cleaning them off, but that's just me purely clutching at straws, could be perfectly fine and the CRT was just on its' last legs anyway...

[@fumthings]

hi Adrian. when it is not sharp like that, is there a focus control? (possibly on the flyback). does it help?

[@eDoc2020]

When only bright parts of the image are unsharp it's not a focus problem.

[@fumthings]

@@eDoc2020 ok, good to know.

[@nekosarantango865]

Tbf tho, when they originally used that glue they werent expecting the utem to still be in use 40 or so later!

[@jeromethiel4323]

Sad, those were good monitors back in the day. The cloth screen was a mistake (even worse were the GLUED ON screens). But no CRT ever lasts forever. The phosphor just wears out over time. I believe the phosphor actually oxidizes, but i might be wrong about that.

[@mrnmrn1]

The phosphor degrades, but definitely not oxidizes, as there's no oxigen inside the CRT. Usually the degradation of cathode emissions what has a bigger effect on the picture quality of the CRT. Cheap rebuilt CRTs had their original phosphors on the screen, and just the guns got replaced, and they were OK to use up a second gun. But when a tube got rebuilt a second time without replacing the phosphor, that was probably not too great I guess.

[@jeromethiel4323]

@@mrnmrn1 Gotcha. But a degraded electron gun won't show patterns of "burn in." And all vacuum tubes have at least some oxygen in them. Those vacuums are not perfect, and even with a getter, there are still stray oxygen floating around in there. But i agree, it's not oxidation, at least not to any measurable value. I wonder if the phosphor actually gets "blown off" from the impacts of the electrons slamming in. In a color tube, those electrons are moving! But phosphor degradation is a slow process. I've owned old monitors that had burn in, but they were on 24/7/365 for 5-6 years before i got them. But hey, free monitors!

[@quayzar1]

Great diagnostic work here but too bad about the tube. Incidentally when I've rejuvenated crts successfully I didn't get that sparking but more of a brighter glow. I suspect that KONG while perhaps okay at testing shouldn't be used for rejuvenation. Also it looks a lot like a B&K Precision 490B. Is it a knock off?

[@hugosimoes5119]

I have a Samsung Syncmaster 753s with the beam forming a line in the middle of the CRT. Probably some IC leg has some bad soldering. I looked all over the place and all seems fine. I don't have the equipment nor do know what to do. The CRT is just catching dust literally. I guess there is something with the deflection.

[@CommodoreGreg]

That's vertical deflection, but first check that there's no service switch in the wrong position.

[@michaelterrell]

If it is a horizontal line, it is likely an open non polarized electrolytic in series with the vertical defeltion winding on the yoke, or a wire has corroded off of one of the yoke terminals. Both used to be common faults.

[@hugosimoes5119]

@@michaelterrell If it is that true, it is a shame. It is a 17" CRT not being used.

[@michaelterrell]

@@hugosimoes5119 You can replace a bad capacitor, and in many cases you repair the yoke by using a piece of component lead or bus wire by soldering it to the terminal, then soldering the broken wire to it. Just don't remove the yoke from a color CRT, because inline tubes are difficult to converge. It is also possible that the vertical drive is missing from he vertical output stage. Many sets use an IC to generate the signal, and to drive the yoke. Most datasheets are online and they detail the pinout and typical circuits.

[@Knaeckebrotsaege]

I've seen this on a bunch of cheaper monitors and TVs. If the line doesn't happen all the time and it reacts to smacking the case, it's definitely cold solder joints, specifically in the vertical deflection area. Whenever that happens, lower the brightness to minimum or you'll risk burning a line in the phosphor in a VERY short time, even just from testing. If you can't lower the brightness (because it's controllable only via OSD or something), best not to turn it on for more than a few secs. If it worked fine before this happened, chances are very high to get it fixed fairly easily (either resoldering the cold joints on the board, or if that doesn't help, checking for bad caps or corroded parts from the brown glue gunk). It's rarely very complicated with this fault

[@evileyeball]

Hey Adrian, Where do you commonly get your supplies of Deoxit? I have never bought any before but have some very scratchy pots on my stereo I want to clean with it. I'm in Canada if that makes a difference.

[@Nas_Atlas]

Amazing fix but we've had enough of the bug zapper. There's not a single 300a for sale on ebay. These things are getting rare!.

[@Dorff_Meister]

Some time into it, do you PREFER the Hantek $60 PC scope or the $125 stand-alone?

[@rickhunt3183]

I was rocking an amdek ttl amber screen

[@Choralone422]

I would echo the other comments about not trying to rejuvenate a CRT unless it's already basically unusable. IMO that process has far to high of a failure rate to use on CRT that is still marginal. And the brown goop strikes again! I wonder how many devices that stuff has claimed the life of over the years! I'm sure it's an obscene number.

[@dmc716]

Ala si ga opravio - svaka ti cast :D

[@asherael]

the spectrum analizer is just showing you the audio spectrum of the monitor running?

[@terryraymond7984]

Adrian we all make mistakes. :-) Reguarding installing the diode backwards

[@maxtornogood]

Ouch, that so called rejuvenation was just the death knell! 😕

[@DavidWonn]

It seems like whenever you rejuvenate, and it happens to make it worse, a 2nd time destroys it altogether.

[@suzakule]

the B&k 490b ( of which i also have one ) was NOT made for rejuvenation smaller CRTs like that, you can test small ones, but if you try rejuvenation, you will destroy them 90% of the time. it was made for TV sized CRTs which had more robust elements, It will DESTROY small tubes like that almost every time, even on the low setting of 25...

[@suzakule]

I have had mine for many years! :p i.imgur.com/czxSDyE.jpg

[@jk180]

Adrian, go check out the TV Museum youtube channel. It may be worth a visit to see what they could do with a rare old CRT. It could be a cool crossover video.

[@frankowalker4662]

I enjoyed the light show. :)

[@Sobakin76]

Looks like it's just freewheeling diode like 1n4148 and not a zener.

[@tcam333]

I had one of these back in the 90s. just went around the edge lightly with a razor blade and cut the mesh off.

[@kaitlyn__L]

That reminds me of how there were tiny pieces of plastic wrap around my guitar’s pickguard pinched against the body… I unscrewed the whole thing to remove those shreds lol. When it was torn off, most of it broke-away at a point which was behind the visible edge when it had snapped back, but with just a couple of exceptions. There was essentially a thin “gasket” left over on the guitar body all the way around after I’d removed the pickguard, lol.

[@gotj]

Tuen off the lights and (in the dark) look at the filament.

[@radio-ged4626]

I wouldn't feel bad about the rejuvinator fail. Even when it does work, many times the tube will start to look bad again a few days later. Most of the time those rejuvinators were used as a temporary fix while the engineer ordered in a replacement tube.