There's something exciting to me regarding the flicker of CRT TV's. Today's TV's can't seem to replicate it. I must say that your verbal high-voltage warning was *quite* enough to cause me to give your video a *thumbs up!* In my country, we say *SAFETY FIRST!*
You should consider doing a few more videos on CRT chassis repair when ever you get the time to. While niche, the arcade and retro gaming community is still using them. Repair is a bit of a dying art form. Not a whole lot of videos out there that go into good details on various board level issues and their fixes either. Enjoyed the vid!
@@12voltvids I do have tiny 8" Sony PVM and 24" Toshiba CRTs that could use some work, if you needed future youtube content. Only thing is that I live in Calgary.
@@12voltvids Shipping crts isnt ideal from what I hear. If I do drive up to BC one day, I'll be sure to contact you in advance encase you are interested in checking them out. Thanks
Awesome! I'm glad that we still have people who care enough to fix things instead of just throwing them in the trash. I hate throwing the entire TV away when all it needs is one new resistor and one new capacitor.
Hi 12voltvids, truly great video as usual, you can work without a schematic, I don't I don't know who was in there before me and God knows what they have changed in the TV, I just can't trust anyone to replace parts with the correct parts, ok if they are close then it may not matter, but watching you repair most things as you say it's ok to use a higher voltage caps in fact it is always better to do so and as you said you can't trust isolation transformers you should not trust them, I find making my own at least I know it is safe to use, I have two tectonics and I love then, I think they are second to none, I see you use the same, it's great to have the knowledge to test anything you work on, I give you the credit for your help in starting in electronics, in the past three years I am finding it so much easier, thanks to you it's a great hobby for me, there is no tec anything as good or explains everything in so much detail. Jeep up the amazing work, it's second to none. 😊👍👍👍
That model of Toshiba TV was the first TV I ever owned (of my own). I recall purchasing it in 2000 at a garage sale, it was gray, not white, and I bought it at the time for $5. My parents said if I wanted a TV in my bedroom, I would have to buy it on my own and bring it home. So I walked to a garage sale about 20 minutes away, bought the small TV, and lugged it home. All I can remember is I had the set for at least 5 years until I bought an LCD TV set to replace it. It was a nice set and had the remote too, and had decent color and actually got all channels (up to ch 125). No need for a VCR.
I remember the smell of the Xcelite plastic handles that my grandfather used as a TV serviceman. Most often used was the red "spinner" and the yellow "spinner". My job as a youngster was to hand him tools, and hold the flashlight.
When you first checked the 12v feed coming from the flyback and you had your hand cupped over it,was I the only one who saw you get a little shock from it Dave. Hop your heart is strong,you don't want too many of those snaps .
I love my CRTs, yeah I've Nintendos and Segas, unfortunately my Coleco is long gone. You know what I really like using them for, watching Star Trek, The Twilight Zone, Outer Limits, and many other great shows. Sure they're remastered and look good on my OLED, but it just feels proper on my 36" Trinitron... 200 lb monster, love it! Also, my OLED which has less than 1500 hours on it already has gone through on panel. Both my Trinitrons working just fine at 18 and 24 years, I wish that technology didn't have to die. oh well, great vid!
These smaller sets usually run the second anode at about 18 Kv. The current is only a few milliamps, which can still be lethal if you have a weak heart, but what really worries me is the VCC+ on the horiz output collector. And yes, RF at 1000v p-p can cause a nasty burn, as the impedance is much lower than that at the output of the HV tripler. Working without an isolation transformer or power plant is crazy, because mains power supplies more than enough energy to kill you dead.
This dude totally knows his way around a TV set. Exudes confidence and experience. I'd be bloody terrified poking around in that thing! Guitar amps I can deal with, TV's... No thanks!! :-)
Guitar amps are every bit as dangerous. You've got 300 or 400 volts at a few hundred milliamps floating around in there. It can definitely send you to the pearly gates.
The crt anode is usually much lower for a small set. I used to figure 1 kv per inch so a set like yours is 15 kv and focus 10% of that so maybe 1500 volts. The spikes on the transistor are about right at 1 kv and can easily damage your scope or dvm so stay off that unless you know the set is dead. Few sets have a live heatsink. Ouch! The 130 volt tells the story. If the oscillator us not running it's more like 156 but running it's 120 to 130. Stay off that HOT!
DMM yes, scope is relatively safe with x10 probe. Scope has 400 p-p input max, so with x10 that would be 4KV. Dony try to measure the plate of a horizontal output on a tube set. Kiss your scope goodbye. The HV is considerably higher than 15kv. That may be accurate for a monochrome set, but a color, the 2nd anode is closer to 25kv on a set this size and 30kv on a 25"
@@12voltvids have you ever had a hv probe? I did and I was quite aware of the anode voltage. I never had 30 kv on any set I worked on. Yes the tube sets had quite the kick. Well keep your dvm off that.
@@12voltvids I fixed so many monitors for video games. Actually many used canadian monitors. Electrohome was in so many early pack man galaga games. It was a stripped down jvc tv. Yes the first thing was to slip my meter on that 220 ohm 20 watt resistor. Some had a bad cap that caused it to fire hv and shut down in a second. 47 uf 250 volt.
HAHAHA @ 13:36 I know that hand movement!!!! I had a good little chuckle, I've been there before 🤣😂 great video as usual and glad to see the other A** has been banned.
Ya I poked myself on a sharp piece of wire sticking out. I get jabbed in the arm with a big needle and don't flinch and a little piece of wire jabs me under the fingernails and I react quick.
"don't try this, i have experience".... blows a fuse when trying it. That shows that you have to be carefull with high voltage, even with a lot of experience.
I hope the owner appreciates your personalizing the set with the nice scratches you put on the unprotected CRT from 1:50 to 2:20, that are visible in every subsequent shot of the tube.
Scratches. Nonsense. Last time I checked glass is harder than wood and even any dirt that might be there. The only thing that is going to scratch glass is a diamond, and I don't have any of those lying on the bench. Besides, it is MY set. I sold him one I had for 20 bucks and took this one off his hands.
How much money would you bet on the screen capacitor going out, and the owner cranking the brightness and contrast all the way up to compensate for it, loading down the video circuit and eventually taking out the low voltage power resistor?
I remember back in the 1970s we had our first colour TV it was a 21 inch screen, it was huge the depth of the TV was about 4 feet, the wood cabinet was about 2 feet and then there was another 2 feet of cardboard covering. I remember looking into the back of the set and seeing a metal cage , that had some glowing valves inside. It wasn’t very reliable and required repairs on a regular basis.
The first color set I saw was my grandmothers Philips K6. Full of tubes and it broke down just about every time it was turned on. Well not quite, but the philips service man was over on a regular basis fixing it. It was a 25" tube. It had about 22 tubes (valves) it is on a vertical circuit board. This was t he problem. The circuit board was a joke, all kinds of bad connections. It was 1967, and I remember watching Neil Armstrong utter those famous words "One small step for a man, one giant leap for mankind" on that TV. Walter Cronkite was in living color, but they only took a black and white camera to the moon. Remember it like it was yesterday. My parents first color set was also a Philips, a modular 4 hybrid. Had 4 tubes, horizontal oscillator, vertical oscillator / output, horizontal output and damper tube. I still remember the horizontal output and damper tube. 40KG6 and 42EC4. They were a series strung filament. The horiz osc was a 12 volt tube and the vertical had 2 tubes internal with series filaments each, so 2x 12v in series. If any of the tube filaments went open they all went out. It would eat the horizontal output tube regularly. Either due to a weak horizontal oscillator tube or an open grid bias resistor. That set had the repairman out on a regular basis too, and of course I was right there learning how it worked. By the mid 70s philips would no longer service the old K6 set. It had the most beautiful color I had ever seen. My grandmother also had the first remote control set I ever saw. A Zenith chromacolor II with the space command remote that used a hammer and a aluminum tube suspended in a plastic insulator. The hammer would strike the end of the tube that produced an ultrasonic ping that the microphone on the tv would detect and advance the channel up or down, or toggle the volume. It had 3 volume settings. Soft, Mid and Loud, and you had to cycle through them, with power off being in the 4th position. That being a modular set also was plagued with troubles. It was probably the first set I fixed.. I would go over and pull the modules clean the contacts and plug them back in and it would work for awhile. I was probably only 10 doing this. It was these 2 TVs that actually got me interested in the repair industry in the first place.
@@12voltvids Those old GE and Magnavox sets with the "griplets". What a PITA those were. My uncle had an old RCA color set from the late 50's / early 60's. When the picture would screw up, he'd bang on the cabinet with fis fist, which would temporarily bring it back.
Whenever I am iffy about some voltage, whether I know it is highly dangerous or if it just unknown to me, I throw on the rubber kitchen type gloves. I bet 30kV can even get through them but then again, I never worked on a CRT and heard the warnings of them since a kid. I would work on one if I needed to, but just never did. "Work" as in try to fix it but probably fail hahaha. Ehhh maybe, maybe not, but probably yes fail as I am not learned very well on them specifically. In completely different subject, I learned a fair amount about 3 phase power systems like in clubs and the like, so to lessen high current potential at any instantaneous time. Cool concept!
You know why the horiz output transformer is called a "flyback"? Because if you come across it on an energized unit, you will fly back across the room. After that, if you're lucky, you can retrace your steps.
I have been bit by the "cobra". You know the HV capacitor on the tube that looks like a cobra and bites like one. The sensation I can describe like hitting your thumb with a hammer. Not recommended.
Actually if you want to know the real reason it's called a flyback is because of what it does. It makes the spot fly back across the screen. It dates back to the days of tubes but even in the transistor era when the horizontal transistor or output tube goes into full conduction you get a huge dump of current through the primary winding of the flyback which saturates the winding. Then the switch turns off which causes the magnetic field to collapse in the primary this produces a large pulse that appears both on the primary about 1000 volts or so and the secondary produces its high voltage pulse approximately 10,000 volts. The secondary connects to a series of diodes and capacitors called the tripler which rectifies that pulse into extreme high voltage or EHT DC approximately 30,000 volts. the pulse returning in the primary when the switch opens is used to charge the horizontal yolk and then he already coils which is what makes the beam fly across the screen when the transistor or tube goes into conduction the discharge rate is controlled through the transistor which causes the beam to travel left to right out of control speed as the capacitor charges in serious with the yoke or the switch turns off this is called the flyback or retrace that's when the magnetic field collapses and you get a huge pulse which kicks the beam back to the other side of the screen extremely quick so that you don't see anything on the screen. Hence the name fly back it causes the scanning beam to fly back across the screen. Of course if you stick your fingers in there you're going to fly back across the room too
@@12voltvids You missed the pun. That one sailed. Fly back across the room - retrace your steps... =whoosh!= Yes, "flyback" or retrace happens during the horizontal blanking interval. If the blanking pulse is weak or absent, or if the kine bias is off a bit, the retrace CAN be faintly seen sometimes. But, of course, I was only kidding about the reason for the slang term "flyback". I was working on old sets in the 70's, even before solid state TV's were popular. In ham radio jargon, when horiz out tubes, such as 6CD6, 6BQ6, etc are used as RF finals, we refer to them as "sweep tubes". they are good well into the 10 meter band, due to their fairly high cutoff frequency of around 60 Mhz. 73
@@12voltvids Yep. My smart-aleck comments are mainly for all viewers who read the comment thread. Cobra - bites like a snake. Just one thing, though: the "capacitor" is actually formed by the aquadag coating (second anode). It doesn't store that much energy, but then again, neither does a defibrillator (which you might need after poking around in there - especially in the horizontal, which can leave you horizontal).
I used to be able to hear the horiz frequency on older TVs which ran at 15750 Hz. Not anymore, since monitors run at a higher horiz refresh rate, usually 37.879 Khz for older VGA monitors. Dogs and cats will probably be able to hear it, tho.
Question... not sure if you'll know but I've got a 96 Zenith tv and about a year or two ago while i was using it, all of a sudden the picture went black, then it flashed a greenish scrambled screen and then the picture returned but when it did, the picture was very dark and the contrast was way off. It now looks dark in some areas and in those dark areas there's a faint purple hue. I check the picture settings just for the hell of it and everything is where I had it set. So I know its an issue with the circuitry. And I was curious as what happened to cause that. the bright areas you really cant notice it. It seems like the brightness/contrast was affected by whatever happened.
Many sets from that era had bad crts. Most of the time would flash green and pic would be horrible after that. Sometimes the the switching mode supply would die too from the high current draw from the bright green flash. Don't know but it was nearly always the green that flashed over. I'm surprised to see one around in 2021 lol
Hi there you removed infrared led recently any chance that you put up a. Video installation on a machine please I would love to see how it's done Thankyou in advance and I always look forward to your new videos
It's a rarity to see someone fixing and selling CRTs. without going too into it, there's a lot of bad sellers on facebook. :) Watching this with my cup o' joe!
My crt TV is a 20 year old Toshiba 19A26 and not a panasonic I use it to play video games and the occasional dvd movies using the male cable connector on the back of the TV instead of using audio/video connectors
I've got a Toshiba CRT that only turns on once when it is first plugged in and then won't turn on again unless unplugged. I'm going to try this. Thanks!
I have way to many crts but I have my favorite old school crt that the power supply blew up and as dumb collage kid I used it for electronic parts for other projects
Hello, I have a Toshiba 34hfx84 that shut off on me and now will only stay on for 5 seconds then shuts off and power light blinks. I’m wondering how likely it is that re-capping the power would fix this? I would really appreciate any advice, would rather not have to throw this tv out (it’s 160 lbs.)
Well done, it didn't take you long to revive the patient. A dead screen voltage filter cap and a feed resistor. The lesson today is: Throw your crap parts away lol. Speedy dave :-D
1:48 You put the tv with the screen down on your workstation and turn the whole thing left and right. Are you not afraid of scratching the glass of the screen?
Nice video! I have an RGB monitor with the exact same ringing issue. It's going to be an easy fix now. Thanks! --- How can I identify the 'screen capacitor'? Is it related to the 'Screen' pot on the flyback?
@@12voltvids 24 volts difference across resistor = unknown I current * 2 ohms resistance, so 24=2x/x=12. Let me know if I did something wrong lol because 12 amps is out of this world
@@walle637 You are forgetting one thing. This is a flyback transformer. The 12 volt tap is on the same winding as other taps. Under no load it will float much higher then 12 volts just due to induction from the HV winding that is also in there. Put a load on it and the voltage goes back to 12 volts. Also remember it is at 15.7khz and when you are dealing with a pulse waveform it will affect the accuracy of the meter. If i put the scope on the open pin the waveform would not be nice and clean like the horizontal output collector. You would see ringing all over the place because the resistor was open.
You say "totally dead" but if the H osc, HOT and flyback are good, wouldn't you at least hear/feel static from the HV coming up? CRT heaters should be getting power too.
I thing you knew it was a bad cap just to show what can happen if you don't test caps, I know you would never do that without thinking, you know far too clever to make that mistake.😀👍👍
It wasn't that I made a mistake my assistant did. He changed the tube and connected the anode cap and had the tv running. I went to adjust the convergence right at the time lightning was planning of shooting out from under the dirty HV cap and my hand was closer than the DAG. After my hand stopped throbbing i removed the cap, cleaned the glass and inside of the cap and put fresh dielectric grease on it. I had a few assistants that didn't have a clue.
@@lstein3372 this guy had been working with me for 10 years so he should have known what he was doing. What happened was while he was changing the tube the boss was on a rampage about something and came in the back and interrupted him to go look for something and when he came back he forgot to clean the tube glass and HV cup. He started forgetting many things in the year that followed. Then one day he didn't show up for work. Turned out he got lost on the way in. Turned the wrong way and ended up in a different town. That was when we figured out he had early onset dimentia and it wasn't long after that he retired and i was by myself. A few years after i left he called me at home to see if i had a belt kit for an RCA VCR. I said I did so he came out and bought it from me and i noticed his wife was driving. The man was only about 60 at the time. He would be about 77 now if he is still alive, but knowing the progression of that condition he won't be in good shape now.
Love that you post the embarrassing fails. You're a good example Dave.
There's something exciting to me regarding the flicker of CRT TV's. Today's TV's can't seem to replicate it. I must say that your verbal high-voltage warning was *quite* enough to cause me to give your video a *thumbs up!* In my country, we say *SAFETY FIRST!*
You should consider doing a few more videos on CRT chassis repair when ever you get the time to. While niche, the arcade and retro gaming community is still using them. Repair is a bit of a dying art form. Not a whole lot of videos out there that go into good details on various board level issues and their fixes either. Enjoyed the vid!
I do have a few kicking around. Must have some fault that needs to be fixed too.
@@12voltvids I do have tiny 8" Sony PVM and 24" Toshiba CRTs that could use some work, if you needed future youtube content. Only thing is that I live in Calgary.
@@abdulalawaz5 that's a little far to ship a CRT
@@12voltvids Shipping crts isnt ideal from what I hear. If I do drive up to BC one day, I'll be sure to contact you in advance encase you are interested in checking them out. Thanks
Your knowledge of those circuits is truly amazing!
Awesome! I'm glad that we still have people who care enough to fix things instead of just throwing them in the trash. I hate throwing the entire TV away when all it needs is one new resistor and one new capacitor.
Yup, as Shango066 says, these sets are "Gamers Choice". 😁
Hi 12voltvids, truly great video as usual, you can work without a schematic, I don't I don't know who was in there before me and God knows what they have changed in the TV, I just can't trust anyone to replace parts with the correct parts, ok if they are close then it may not matter, but watching you repair most things as you say it's ok to use a higher voltage caps in fact it is always better to do so and as you said you can't trust isolation transformers you should not trust them, I find making my own at least I know it is safe to use, I have two tectonics and I love then, I think they are second to none, I see you use the same, it's great to have the knowledge to test anything you work on, I give you the credit for your help in starting in electronics, in the past three years I am finding it so much easier, thanks to you it's a great hobby for me, there is no tec anything as good or explains everything in so much detail. Jeep up the amazing work, it's second to none. 😊👍👍👍
That model of Toshiba TV was the first TV I ever owned (of my own). I recall purchasing it in 2000 at a garage sale, it was gray, not white, and I bought it at the time for $5. My parents said if I wanted a TV in my bedroom, I would have to buy it on my own and bring it home. So I walked to a garage sale about 20 minutes away, bought the small TV, and lugged it home. All I can remember is I had the set for at least 5 years until I bought an LCD TV set to replace it. It was a nice set and had the remote too, and had decent color and actually got all channels (up to ch 125). No need for a VCR.
I remember the smell of the Xcelite plastic handles that my grandfather used as a TV serviceman. Most often used was the red "spinner" and the yellow "spinner". My job as a youngster was to hand him tools, and hold the flashlight.
When you first checked the 12v feed coming from the flyback and you had your hand cupped over it,was I the only one who saw you get a little shock from it Dave.
Hop your heart is strong,you don't want too many of those snaps .
I didn't get a shock. Nothing. I did jab my hand on a sharp piece of wire sticking through the board. It was turned off when I was maneuvering it.
OK Dave,phew .
@@12voltvids However, as you know the HT lead holds a lot of charge, for years sometimes.
I love my CRTs, yeah I've Nintendos and Segas, unfortunately my Coleco is long gone. You know what I really like using them for, watching Star Trek, The Twilight Zone, Outer Limits, and many other great shows. Sure they're remastered and look good on my OLED, but it just feels proper on my 36" Trinitron... 200 lb monster, love it!
Also, my OLED which has less than 1500 hours on it already has gone through on panel. Both my Trinitrons working just fine at 18 and 24 years, I wish that technology didn't have to die.
oh well, great vid!
My plasma is 12 years old and has 15000 hours in it. Still going strong.
These smaller sets usually run the second anode at about 18 Kv. The current is only a few milliamps, which can still be lethal if you have a weak heart, but what really worries me is the VCC+ on the horiz output collector. And yes, RF at 1000v p-p can cause a nasty burn, as the impedance is much lower than that at the output of the HV tripler. Working without an isolation transformer or power plant is crazy, because mains power supplies more than enough energy to kill you dead.
This dude totally knows his way around a TV set. Exudes confidence and experience. I'd be bloody terrified poking around in that thing! Guitar amps I can deal with, TV's... No thanks!! :-)
Guitar amps are every bit as dangerous. You've got 300 or 400 volts at a few hundred milliamps floating around in there. It can definitely send you to the pearly gates.
@@gyrgrls Hi there! It certainly can - and they're DC voltages too. Deadly. However, I know what I can and what I can't poke in an amp 😜
I showed this to my son- I said- This guys an honest engineer- it doesnt always go smoothly like Holywood....
Always love your CRT videos Dave, keep it up!
Very informative thanks again Dave
Screen cap for ringing. Good to know. Love the CRT vids.
The crt anode is usually much lower for a small set. I used to figure 1 kv per inch so a set like yours is 15 kv and focus 10% of that so maybe 1500 volts. The spikes on the transistor are about right at 1 kv and can easily damage your scope or dvm so stay off that unless you know the set is dead. Few sets have a live heatsink. Ouch! The 130 volt tells the story. If the oscillator us not running it's more like 156 but running it's 120 to 130. Stay off that HOT!
DMM yes, scope is relatively safe with x10 probe. Scope has 400 p-p input max, so with x10 that would be 4KV. Dony try to measure the plate of a horizontal output on a tube set. Kiss your scope goodbye. The HV is considerably higher than 15kv. That may be accurate for a monochrome set, but a color, the 2nd anode is closer to 25kv on a set this size and 30kv on a 25"
@@12voltvids have you ever had a hv probe? I did and I was quite aware of the anode voltage. I never had 30 kv on any set I worked on. Yes the tube sets had quite the kick. Well keep your dvm off that.
@@markanderson350 yes i had one at the shop. It was a HV probe for my vtvm. That was the shops though not mine so it didn't leave when i did.
@@12voltvids I fixed so many monitors for video games. Actually many used canadian monitors. Electrohome was in so many early pack man galaga games. It was a stripped down jvc tv. Yes the first thing was to slip my meter on that 220 ohm 20 watt resistor. Some had a bad cap that caused it to fire hv and shut down in a second. 47 uf 250 volt.
HAHAHA @ 13:36 I know that hand movement!!!! I had a good little chuckle, I've been there before 🤣😂 great video as usual and glad to see the other A** has been banned.
He is still firing off complaints but they go nowhere. He's a real nowhere man living in his nowhere land!
Ya I poked myself on a sharp piece of wire sticking out. I get jabbed in the arm with a big needle and don't flinch and a little piece of wire jabs me under the fingernails and I react quick.
"don't try this, i have experience".... blows a fuse when trying it.
That shows that you have to be carefull with high voltage, even with a lot of experience.
I hope the owner appreciates your personalizing the set with the nice scratches you put on the unprotected CRT from 1:50 to 2:20, that are visible in every subsequent shot of the tube.
Scratches. Nonsense. Last time I checked glass is harder than wood and even any dirt that might be there. The only thing that is going to scratch glass is a diamond, and I don't have any of those lying on the bench. Besides, it is MY set. I sold him one I had for 20 bucks and took this one off his hands.
I'd like to see you do any better....Oh that's right...I forgot.... You only know how to criticize & have no skill...(my bad)
@@russb8151 I couldn't have said it better myself LOL
might have scratched the anti glare coating but not the glass
@@elektrokinesis4150 anti glare on that. Not likely.
My favourite repairs are the "no power" completely dead ones
How much money would you bet on the screen capacitor going out, and the owner cranking the brightness and contrast all the way up to compensate for it, loading down the video circuit and eventually taking out the low voltage power resistor?
Zero. Not enough beam current to draw enough to blow resistor.
I remember back in the 1970s we had our first colour TV it was a 21 inch screen, it was huge the depth of the TV was about 4 feet, the wood cabinet was about 2 feet and then there was another 2 feet of cardboard covering. I remember looking into the back of the set and seeing a metal cage , that had some glowing valves inside. It wasn’t very reliable and required repairs on a regular basis.
The first color set I saw was my grandmothers Philips K6. Full of tubes and it broke down just about every time it was turned on. Well not quite, but the philips service man was over on a regular basis fixing it. It was a 25" tube. It had about 22 tubes (valves) it is on a vertical circuit board. This was t he problem. The circuit board was a joke, all kinds of bad connections. It was 1967, and I remember watching Neil Armstrong utter those famous words "One small step for a man, one giant leap for mankind" on that TV. Walter Cronkite was in living color, but they only took a black and white camera to the moon. Remember it like it was yesterday. My parents first color set was also a Philips, a modular 4 hybrid. Had 4 tubes, horizontal oscillator, vertical oscillator / output, horizontal output and damper tube. I still remember the horizontal output and damper tube. 40KG6 and 42EC4. They were a series strung filament. The horiz osc was a 12 volt tube and the vertical had 2 tubes internal with series filaments each, so 2x 12v in series.
If any of the tube filaments went open they all went out. It would eat the horizontal output tube regularly. Either due to a weak horizontal oscillator tube or an open grid bias resistor.
That set had the repairman out on a regular basis too, and of course I was right there learning how it worked. By the mid 70s philips would no longer service the old K6 set. It had the most beautiful color I had ever seen. My grandmother also had the first remote control set I ever saw. A Zenith chromacolor II with the space command remote that used a hammer and a aluminum tube suspended in a plastic insulator. The hammer would strike the end of the tube that produced an ultrasonic ping that the microphone on the tv would detect and advance the channel up or down, or toggle the volume.
It had 3 volume settings. Soft, Mid and Loud, and you had to cycle through them, with power off being in the 4th position. That being a modular set also was plagued with troubles. It was probably the first set I fixed.. I would go over and pull the modules clean the contacts and plug them back in and it would work for awhile. I was probably only 10 doing this. It was these 2 TVs that actually got me interested in the repair industry in the first place.
@@12voltvids Those old GE and Magnavox sets with the "griplets". What a PITA those were. My uncle had an old RCA color set from the late 50's / early 60's. When the picture would screw up, he'd bang on the cabinet with fis fist, which would temporarily bring it back.
Whenever I am iffy about some voltage, whether I know it is highly dangerous or if it just unknown to me, I throw on the rubber kitchen type gloves. I bet 30kV can even get through them but then again, I never worked on a CRT and heard the warnings of them since a kid. I would work on one if I needed to, but just never did. "Work" as in try to fix it but probably fail hahaha. Ehhh maybe, maybe not, but probably yes fail as I am not learned very well on them specifically. In completely different subject, I learned a fair amount about 3 phase power systems like in clubs and the like, so to lessen high current potential at any instantaneous time. Cool concept!
I have 7200 volt lineman's gloves in my truck and they are about 1/8" thick and go inside a leather glove.
Great! I haven't seen you repair many vintage sets.
you are the only guy on youtube who knows what he's doing
Great video, thanks for sharing the knowledge.
Dope ... :D I always feel sad when i mess up my stuff like this.
You know why the horiz output transformer is called a "flyback"? Because if you come across it on an energized unit, you will fly back across the room. After that, if you're lucky, you can retrace your steps.
I have been bit by the "cobra". You know the HV capacitor on the tube that looks like a cobra and bites like one. The sensation I can describe like hitting your thumb with a hammer. Not recommended.
Actually if you want to know the real reason it's called a flyback is because of what it does. It makes the spot fly back across the screen. It dates back to the days of tubes but even in the transistor era when the horizontal transistor or output tube goes into full conduction you get a huge dump of current through the primary winding of the flyback which saturates the winding. Then the switch turns off which causes the magnetic field to collapse in the primary this produces a large pulse that appears both on the primary about 1000 volts or so and the secondary produces its high voltage pulse approximately 10,000 volts. The secondary connects to a series of diodes and capacitors called the tripler which rectifies that pulse into extreme high voltage or EHT DC approximately 30,000 volts. the pulse returning in the primary when the switch opens is used to charge the horizontal yolk and then he already coils which is what makes the beam fly across the screen when the transistor or tube goes into conduction the discharge rate is controlled through the transistor which causes the beam to travel left to right out of control speed as the capacitor charges in serious with the yoke or the switch turns off this is called the flyback or retrace that's when the magnetic field collapses and you get a huge pulse which kicks the beam back to the other side of the screen extremely quick so that you don't see anything on the screen. Hence the name fly back it causes the scanning beam to fly back across the screen. Of course if you stick your fingers in there you're going to fly back across the room too
@@12voltvids You missed the pun. That one sailed. Fly back across the room - retrace your steps... =whoosh!= Yes, "flyback" or retrace happens during the horizontal blanking interval. If the blanking pulse is weak or absent, or if the kine bias is off a bit, the retrace CAN be faintly seen sometimes. But, of course, I was only kidding about the reason for the slang term "flyback". I was working on old sets in the 70's, even before solid state TV's were popular. In ham radio jargon, when horiz out tubes, such as 6CD6, 6BQ6, etc are used as RF finals, we refer to them as "sweep tubes". they are good well into the 10 meter band, due to their fairly high cutoff frequency of around 60 Mhz.
73
@@gyrgrls Yes I got it. It was soooo funny I forgot to laugh. Heard them all before. Same goes for the "cobra"
@@12voltvids Yep. My smart-aleck comments are mainly for all viewers who read the comment thread. Cobra - bites like a snake. Just one thing, though: the "capacitor" is actually formed by the aquadag coating (second anode). It doesn't store that much energy, but then again, neither does a defibrillator (which you might need after poking around in there - especially in the horizontal, which can leave you horizontal).
Love the TV episodes!!
I used to be able to hear the horiz frequency on older TVs which ran at 15750 Hz. Not anymore, since monitors run at a higher horiz refresh rate, usually 37.879 Khz for older VGA monitors. Dogs and cats will probably be able to hear it, tho.
Question... not sure if you'll know but I've got a 96 Zenith tv and about a year or two ago while i was using it, all of a sudden the picture went black, then it flashed a greenish scrambled screen and then the picture returned but when it did, the picture was very dark and the contrast was way off. It now looks dark in some areas and in those dark areas there's a faint purple hue. I check the picture settings just for the hell of it and everything is where I had it set. So I know its an issue with the circuitry. And I was curious as what happened to cause that. the bright areas you really cant notice it. It seems like the brightness/contrast was affected by whatever happened.
Many sets from that era had bad crts. Most of the time would flash green and pic would be horrible after that. Sometimes the the switching mode supply would die too from the high current draw from the bright green flash. Don't know but it was nearly always the green that flashed over. I'm surprised to see one around in 2021 lol
Really cool video! What a coincidence that it just happened to be a screen capacitor video
I have a CRT that's not doing what it should, I'm at the limit of my understanding and experience at this point. Is there any way we can discuss it?
Hi there you removed infrared led recently any chance that you put up a. Video installation on a machine please
I would love to see how it's done
Thankyou in advance and I always look forward to your new videos
It's a rarity to see someone fixing and selling CRTs. without going too into it, there's a lot of bad sellers on facebook. :) Watching this with my cup o' joe!
They are not worth much.
stuff i still learn from other vid and this one. good to know about the screen cap as ive seen some tv's like that before.
You should also check out Jordan Pier if you like to watch old CRT TVs being fixed, and Shango066 as well.
Can you not just isolate the composite input ground from the chassis in the same way the RF input is isolated?
I've got a 20 year old Panasonic crt tv still going strong because I use power strips that are surge protected, no problems with my electronics!..:)
I use surge protection on everything.
My crt TV is a 20 year old Toshiba 19A26 and not a panasonic I use it to play video games and the occasional dvd movies using the male cable connector on the back of the TV instead of using audio/video connectors
I've got a Toshiba CRT that only turns on once when it is first plugged in and then won't turn on again unless unplugged. I'm going to try this. Thanks!
How would you check if there was high voltage without a scope?
Definitely NOT the wet finger trick.
@@12voltvids HV probes are fairly cheap now. :)
I have way to many crts but I have my favorite old school crt that the power supply blew up and as dumb collage kid I used it for electronic parts for other projects
Hello, I have a Toshiba 34hfx84 that shut off on me and now will only stay on for 5 seconds then shuts off and power light blinks. I’m wondering how likely it is that re-capping the power would fix this? I would really appreciate any advice, would rather not have to throw this tv out (it’s 160 lbs.)
I've always wanted one of those CRT HDTV's. They have much better colors than LCD sets.
Wow, my sister's old TV has these vertical lines, I will repair it for her!
Let me know the progress on if it works!
Well done, it didn't take you long to revive the patient.
A dead screen voltage filter cap and a feed resistor.
The lesson today is: Throw your crap parts away lol.
Speedy dave :-D
1:48 You put the tv with the screen down on your workstation and turn the whole thing left and right. Are you not afraid of scratching the glass of the screen?
Not at all. Glass is harder than wood.
@@12voltvids The glass is harder indeed, but the dust?
@@dirkjachimsky9401 I don't see any diamond dust on my bench.
excellent video, thank you
Im scared of CRTs. I get a bit nervous when you are touching the board (13.37min) 😂
Nice video! I have an RGB monitor with the exact same ringing issue. It's going to be an easy fix now. Thanks! --- How can I identify the 'screen capacitor'? Is it related to the 'Screen' pot on the flyback?
The cap that came out only had one leg left. The neg terminal came right out.
@@12voltvids How to tell a screen capacitor apart from the others?
@@csabasanta5696 its for the 200v crt supply. Usually 10 to 33 uf at 250 volt. Its usually near the flyback.
@@marka1986 Managed to find it using your info and the schematics. Thank you!
@@csabasanta5696 glad it was helpful
Do you isolate your oscilloscope as well? Awesome video thank you.
Nice one Dave! Blew up the customers TV...
Blew a fuse big deal.
@@12voltvids I had a good laugh. Nice video.
@@ricfair9919 Actually it is my TV. I already sold him one I had sitting in the shop.
I had a evil thought put the links to all the music you use in you're video description. That might send those false copyright claims packing.
No it doesn't. I have done that and the claims still happening and have to dispute. It's an automated system.
Wait what? A 24 voltage drop from 36 to 12 volts and a 2 ohm resistor? No way this thing is running at 12 amps wtf
How do you come up with 12 amps?
@@12voltvids 24 volts difference across resistor = unknown I current * 2 ohms resistance, so 24=2x/x=12. Let me know if I did something wrong lol because 12 amps is out of this world
@@walle637
You are forgetting one thing. This is a flyback transformer. The 12 volt tap is on the same winding as other taps. Under no load it will float much higher then 12 volts just due to induction from the HV winding that is also in there. Put a load on it and the voltage goes back to 12 volts. Also remember it is at 15.7khz and when you are dealing with a pulse waveform it will affect the accuracy of the meter. If i put the scope on the open pin the waveform would not be nice and clean like the horizontal output collector. You would see ringing all over the place because the resistor was open.
When was the tv manufactured, dave?
88 i believe.
@@12voltvids THAT OLD?! i was expecting it to be 10 years newer than that.
@@austinthevhsvideogamelover5265
That was a guess. Late 80s or early 90s. No AV inputs which the later ones all had.
Good Safety Warning...
You say "totally dead" but if the H osc, HOT and flyback are good, wouldn't you at least hear/feel static from the HV coming up? CRT heaters should be getting power too.
Even though HT was there and yes you can feel it pull the hair on the back of your arm it the complaint was dead.
No kitty?
yes dont worry soon you gonna have to fix the digital board on your scope ....
Experience.
13:36 you get a shock? as quick as you let go of that it looked like you did
Fooled ya. Unit was not powered up. I was just trying to be like elextroboom
Thanks !!
I thing you knew it was a bad cap just to show what can happen if you don't test caps, I know you would never do that without thinking, you know far too clever to make that mistake.😀👍👍
i love crt rrpair.
this repair Nish almost gone
More CRT TV's !!!
CRT paradise I have a Toshiba 13" 2005
Gold
You could have used the belt you got from the FB transformer as a teaching moment. A warning that even seasoned technicians make mistakes!
It wasn't that I made a mistake my assistant did. He changed the tube and connected the anode cap and had the tv running. I went to adjust the convergence right at the time lightning was planning of shooting out from under the dirty HV cap and my hand was closer than the DAG. After my hand stopped throbbing i removed the cap, cleaned the glass and inside of the cap and put fresh dielectric grease on it.
I had a few assistants that didn't have a clue.
@@12voltvids The mistake you made then was trusting your assistant to do the job properly without checking his work before touching it.
@@lstein3372 this guy had been working with me for 10 years so he should have known what he was doing. What happened was while he was changing the tube the boss was on a rampage about something and came in the back and interrupted him to go look for something and when he came back he forgot to clean the tube glass and HV cup. He started forgetting many things in the year that followed. Then one day he didn't show up for work. Turned out he got lost on the way in. Turned the wrong way and ended up in a different town. That was when we figured out he had early onset dimentia and it wasn't long after that he retired and i was by myself. A few years after i left he called me at home to see if i had a belt kit for an RCA VCR. I said I did so he came out and bought it from me and i noticed his wife was driving. The man was only about 60 at the time. He would be about 77 now if he is still alive, but knowing the progression of that condition he won't be in good shape now.
The audio is terrible