While upgrading to a new color LCD is cool, I'd learn more from watching you diagnose the problem with the CRT. Systematic diagnosis; looking for obvious issues, then going section by section until the problem is found. That would be awesome.
The problem is you can't probe this with the power on. So no ability to do even basic powered-on measurements. All you can do is dick around randomly checking components in-circuit, or sucking them out and checking.
Solder the testleads you need, pull them trough a venthohle and power it up to measure (short version) or build a temporary extention to power it outside the housing, there aren't so much signals and lines going to the CRT Unit(longer version) ;) Nice greets from Germany/Denmark
Viewers! Date at time index 1:35 you said take the screws off to remove the CRT Frame. UH don't do that until you pull out the control panel, it just pops off, if you don't you can rip the control ribbon on the CRT Front Frame. Here's some good info for you Dave when I did the research on this for mine. I have the LCD but never put it in. IT WORKS GREAT though sitting next to it. LCD types & Dimension Info below. Dave, Here's some Important LCD info for ya. -The LCD EXTERIOR dimensions need to be no larger than: Note the depth can be deeper than 1/2" but you will have to make some offset brackets to compensate for the deeper depth. Standard: 1/2" X 6-5/8 (6.64)" X 5-1/4 (5.25)" Metric: 127 mm X 168.65 mm X 133.35 mm -The ACTIVE/VEIWABLE AREA dimensions needs to be no larger than: Standard: 4.4" down X 5-5/8" across. Diagonally: 7.2" Metric: 111.76 mm X 143.4 mm. Diagonally: 182.88 mm. -The Active area, for best original ratio, MUST be a ratio of 4/3, here are some example ratio resolutions that should work if the screen is a 7" diagonal: 800x600: 1024x768 & 1280x960. To figure out if the Aspect ratio dimensions are 4/3 divide the large number by 4, then multiply the answer by 3. Then you will have the Horizontal x Vertical numbers you need. Ie. 1280/4 = 320, 320 x 3 = 960. So the screen you need is 1280x960 for a 4/3 aspect ratio. I don't know the resolution of the VGA out so I don't know if larger resolution screens will even make a difference in clarity. So until I do the experiment, or someone tells me, the 800 x 600 will have to do. I put this information in my TDS744A project here: If you want to see it. th-cam.com/video/xv_ldH1dZMc/w-d-xo.html Keep up the great work Dave! Best Wishes n Blessings. Keith Noneya Oh PS fix that CRT so I can fix mine LOL. Keith
Just so you know Dave since I gotten back into electronics. Something that has given me purpose to stay on this planet since being disabled 13 or so years ago. You have gotten me dumpster diving looking for a scope or bench meter. No luck yet ,but all the good stuff you've found keeps me looking,lol .
Bummer. From what I saw, it looked like a weak horizontal drive that caused a low high voltage. Were you able to ring test the flyback? Check the horizontal output transistor?
This sounds so much like a techo-babble joke, but I know enough to know its actually real stuff he's talking about, just don't quite know what it means :P
Maybe he should ask on one of the vintage radio/TV forums (i.e. vintage-radio.net) as they are generally a wealth of knowledge on CRT displays/drivers, primarily as some of them used to repair them for a living.
Mrlithium, it means that the voltage for the vertical deflection circuit was traditionally generated in the flyback transformer in CRT circuits these days so when the horizontal transistor, the horizontal transistors line or the horizontal flyback goes partswise bad the vertical will go bad also. In that case the logic order to measure for the fault is to testing: HOT-> HOTs line-> flyback output for horizontal (in case of diode split flyback keep an eye on symmetry of the outputs AC because it could point to defective rectrification diodes in the horizontal secondary part of the flyback)->vertical driver/circuit........I repaired TVs and recorders a lot in my educational time and i was able to be woken up at 3 in the morning to be asked stuff like that in the end :D Nice greets from Germany
Don't change it to chinese rubish LCD panel! Repair and keep original CRT! It's a soul of this scope! Best greetings from Poland, and good luck in repairing :-)
Discharging the CRT is easy once one has been brave enough to do it the first couple of times. Find some reputable advice online that doesn’t involve putting your tongue on it, and she’ll be right. It’s a good idea to do it once, wait a couple of minutes, then do it again. Very often a charge builds back up, and you’ll hear a somewhat smaller “tick” the second time.
On the Tek TDS scopes, the CRT usually comes out as an entire separate module - frame, driver board, and all. Not sure about this unit, but the last one I rebuilt and restored, a TDS 420A was this way. You would remove 5 screws and the whole unit lifts up out of the chassis, making it very easy to access everything. TDS scopes of this era have been notorious for bad caps as well. The TDS 420A I just finished repairing had so many failed electrolytics - some were physically leaking and had corroded the traces and other components on the acquisition, attenuator, and power supply boards - that I said the hell with it and replaced them all. Over 100 of them in all throughout the scope. It works great now, and is one hell of a scope for the money, but it's a bit of work to get them going again. Just saying that you might want to check the main power supply as well. It might work on the VGA output, but there could be an issue with the rails for the CRT board.
Looks like the vertical deflection is far down, try to measure the vertical coils if theres some continous DC on the Signal, if yes i would expect the drivers output transistors to be cactus if no try to measure input signals and voltages of the driver. Good luck by the way for the "colour" mod later, i had the same scope once and did the same project which was a pain in the a... because i did't had a hot air station then, try to add the 2F FFT function also as long as you got it open, it's just a bit of editing in the Dallas RTC (take a copy of it as soon as it works and do the CR2032 mod with the chip) ;) Just a pitty that I lost that scope after all that effort in a bigger incident in march 2017
The anode cap to CRT go bad and arc causing dim, or arcing to frame and CRT won't turn on as a result. See spot where it arc over on side of frame. RTV over the anode cap usually fixes it. Just use clear RTV and let it cure for a day.
Once I bought a 30 years old scope (it was comlitely analog). But after few hours of work horizontal line disappeared from screen. Thankfully I had a manual and after some investigation found that problem was in CRT's drive output transistors (don't remember vertical or horizontal coil). But I was able to find broken transistors only when scope was switched on. Without powering it on transistors seemed normal.
Looking at the adjustments on the main board, it *does* look like you can run the CRT without the scope because it's a regular VGA monitor, with the 16-pin ribbon cable feeding video. VGA is nothing more than a set of analog R/G/B signals (which are probably mixed together on this mono screen) and a TTL-compatible pulse to trigger horizontal and vertical sync. That will take up 10 pins, with the remaining pins probably providing the power voltages required, it should be pretty easy to figure out which pin does what by scoping them, you'd need a high-bandwidth scope though, like the one you're trying to fix ;-)
Dave, check the deflection coils for resistance; and I would also suggest checking their control transistors/immediate circuits for good gates etc... should be able to do some off-line probing to possibly find the issue....
You need to find the adjustment pots and give them a turn while it's on and see if you can affect the picture in both directions or not. You also need to see if the screen pot (usually on the flyback) makes the screen brighter or not (be prepared to get a slight shock if the flyback is faulty). This will let you know if the problem is horizontal deflection, vertical deflection, or the flyback.
Query Please Twice. Not many scopes use magnetic deflection. Most I thought used electrostatic due to the faster speed. This scope use the magnetic cause it has some on screen display capabilities other than just the trace? Thank you.
You showed us a high voltage probe adapter in the last video. Use it to check the screen voltage and horizontal, vertical waveforms. My money is on a power supply problem... Cheers, - Eddy
You can run the driver board external to the chassis. Reconnect the ribbon cable, reconnect the CRT, and it should run. Of course, you have to be careful with positioning, but this will allow you to measure voltages and probe around. Check the linear regulator output first, then have a look at the 50V and 500V rails. My guess is the failure is in the linear regulator, or in the flyback transformer (or driver). If you have a good 50V and/or 500V rail, then the flyback driver and H-sync path is probably all good. You can still have a flyback failure on the CRT anode HV though.
If the flyback supply is working and buzzing then it will probably be the high voltage transformer the culprit. It must be a very obtainable part. CRT devices needed this changed all the time for repair until they were obsoleted in the late 2000s
Yesssss !!! Thanks for trying to fix it ! Please do a giveaway of this. Make it open to everyone and I am sure just for once you could afford international shipping if its an overseas winner ;)
I wanna see Dave use mathematics for integration and/or implementation into a theoretical system and a bode-plot. Theory only and a whiteboard ofcourse 😎 challenge accepted?
Okurka it’s true that it probably isn’t lethal, but there is still risk of nasty injuries, such as whacking your hand against a sharp object as it jumps wildly from the jolt.
I actually met someone who was a specialist in fixing CRTs, and had a few high voltage shocks on these things. Damages to its motoneurons left him with a hand permanently shaking. How practical for soldering! Seriously, never ever toys with CRT without discharging them. It's easy, it is nothing but a capacitor. So before unplugging anything, connect an alligator clip to a screwdriver, the other lead to the ground of the device, lift the skirt of the suction cup (you naughty!), blindly probing for the hole (this is getting pornographic) until the bad boy discharge (here we are). Then you can disassemble everything. Some CRT have auto-discharge circuitry, some does not hold the charge for long, but anyway, never tick the dragon tail, better probe its hole before anything.
@@gerrymacdonald5435 Actually there has been lots of people killed working on older TV's since most of the picture tubes runs on 17KV to 32KV by using a EHT/flyback transformer which converts line level 120v/220v to 17KV - 32KV as required by the specific picture tube.
Yeah but it's 90's era Java based, if you already know it or want to learn it then awesome. I personally wouldn't want to go down that rabbit hole again unless I absolutely had to.
@@zer0b0t yeah I decided to go down the C path, just far enough to get a LCD display and some sensors working on an arduino, that's been fun. So many gadgets, so little time.
Please don't upgrade anything even for better performance, just keep it as is. If you could not or wish not to fix it anyway then resell it as is and get your commission and I will buy.... YOU PEOPLE DON"T LIKE ANTIQUES AT ALL !!!.
While upgrading to a new color LCD is cool, I'd learn more from watching you diagnose the problem with the CRT. Systematic diagnosis; looking for obvious issues, then going section by section until the problem is found. That would be awesome.
^ Agreed.
The problem is you can't probe this with the power on. So no ability to do even basic powered-on measurements. All you can do is dick around randomly checking components in-circuit, or sucking them out and checking.
Solder the testleads you need, pull them trough a venthohle and power it up to measure (short version) or build a temporary extention to power it outside the housing, there aren't so much signals and lines going to the CRT Unit(longer version) ;) Nice greets from Germany/Denmark
Me too, but if a colour upgrade is an option, killing two with one, sadly I would opt for the LCD option
Its pretty dangerous to mess around with CRT. Not worth it.
One day Dave will fix something😊
lmao, really
Dave has fixed lots of gear
lol!
lol. Story of our lives :P
'@@MacVision3D Just not on camera. One day... lol
Viewers! Date at time index 1:35 you said take the screws off to remove the CRT Frame. UH don't do that until you pull out the control panel, it just pops off, if you don't you can rip the control ribbon on the CRT Front Frame. Here's some good info for you Dave when I did the research on this for mine. I have the LCD but never put it in. IT WORKS GREAT though sitting next to it. LCD types & Dimension Info below.
Dave, Here's some Important LCD info for ya.
-The LCD EXTERIOR dimensions need to be no larger than: Note the depth can be deeper than 1/2" but you will have to make some offset brackets to compensate for the deeper depth. Standard: 1/2" X 6-5/8 (6.64)" X 5-1/4 (5.25)" Metric: 127 mm X 168.65 mm X 133.35 mm
-The ACTIVE/VEIWABLE AREA dimensions needs to be no larger than: Standard: 4.4" down X 5-5/8" across. Diagonally: 7.2" Metric: 111.76 mm X 143.4 mm. Diagonally: 182.88 mm.
-The Active area, for best original ratio, MUST be a ratio of 4/3, here are some example ratio resolutions that should work if the screen is a 7" diagonal: 800x600: 1024x768 & 1280x960. To figure out if the Aspect ratio dimensions are 4/3 divide the large number by 4, then multiply the answer by 3. Then you will have the Horizontal x Vertical numbers you need. Ie. 1280/4 = 320, 320 x 3 = 960. So the screen you need is 1280x960 for a 4/3 aspect ratio. I don't know the resolution of the VGA out so I don't know if larger resolution screens will even make a difference in clarity. So until I do the experiment, or someone tells me, the 800 x 600 will have to do.
I put this information in my TDS744A project here: If you want to see it. th-cam.com/video/xv_ldH1dZMc/w-d-xo.html Keep up the great work Dave! Best Wishes n Blessings. Keith Noneya Oh PS fix that CRT so I can fix mine LOL. Keith
Any determined term for "Part 2" or did the scope die during the great lab flood?
Just so you know Dave since I gotten back into electronics. Something that has given me purpose to stay on this planet since being disabled 13 or so years ago. You have gotten me dumpster diving looking for a scope or bench meter. No luck yet ,but all the good stuff you've found keeps me looking,lol .
Crt's are more fun than lcd panels! Good luck with the repair!
Bummer. From what I saw, it looked like a weak horizontal drive that caused a low high voltage. Were you able to ring test the flyback? Check the horizontal output transistor?
I think your right
This sounds so much like a techo-babble joke, but I know enough to know its actually real stuff he's talking about, just don't quite know what it means :P
Maybe he should ask on one of the vintage radio/TV forums (i.e. vintage-radio.net) as they are generally a wealth of knowledge on CRT displays/drivers, primarily as some of them used to repair them for a living.
Mrlithium, it means that the voltage for the vertical deflection circuit was traditionally generated in the flyback transformer in CRT circuits these days so when the horizontal transistor, the horizontal transistors line or the horizontal flyback goes partswise bad the vertical will go bad also. In that case the logic order to measure for the fault is to testing: HOT-> HOTs line-> flyback output for horizontal (in case of diode split flyback keep an eye on symmetry of the outputs AC because it could point to defective rectrification diodes in the horizontal secondary part of the flyback)->vertical driver/circuit........I repaired TVs and recorders a lot in my educational time and i was able to be woken up at 3 in the morning to be asked stuff like that in the end :D Nice greets from Germany
The troubles of low high voltage!
Hey Dave, another useful mod would be to replace the floppy drive with a USB / SD card reader :-)
The colour LCD will be a nice upgrade and add an SD card reader instead of the FDD/HDD
Noooo .. It is shit thing , forging history for ANTIQUES is just like killing someone.
I'd use the commercial LCD kit, it doesn't use the VGA connector, goes directly to the ramdac and alike. Sounds pretty good, but still pricey.
Don't change it to chinese rubish LCD panel! Repair and keep original CRT! It's a soul of this scope! Best greetings from Poland, and good luck in repairing :-)
Discharging the CRT is easy once one has been brave enough to do it the first couple of times. Find some reputable advice online that doesn’t involve putting your tongue on it, and she’ll be right.
It’s a good idea to do it once, wait a couple of minutes, then do it again. Very often a charge builds back up, and you’ll hear a somewhat smaller “tick” the second time.
On the Tek TDS scopes, the CRT usually comes out as an entire separate module - frame, driver board, and all. Not sure about this unit, but the last one I rebuilt and restored, a TDS 420A was this way. You would remove 5 screws and the whole unit lifts up out of the chassis, making it very easy to access everything.
TDS scopes of this era have been notorious for bad caps as well. The TDS 420A I just finished repairing had so many failed electrolytics - some were physically leaking and had corroded the traces and other components on the acquisition, attenuator, and power supply boards - that I said the hell with it and replaced them all. Over 100 of them in all throughout the scope. It works great now, and is one hell of a scope for the money, but it's a bit of work to get them going again.
Just saying that you might want to check the main power supply as well. It might work on the VGA output, but there could be an issue with the rails for the CRT board.
Looks like the vertical deflection is far down, try to measure the vertical coils if theres some continous DC on the Signal, if yes i would expect the drivers output transistors to be cactus if no try to measure input signals and voltages of the driver. Good luck by the way for the "colour" mod later, i had the same scope once and did the same project which was a pain in the a... because i did't had a hot air station then, try to add the 2F FFT function also as long as you got it open, it's just a bit of editing in the Dallas RTC (take a copy of it as soon as it works and do the CR2032 mod with the chip) ;) Just a pitty that I lost that scope after all that effort in a bigger incident in march 2017
Would like to see the CRT fixed before you replace it if possible.
"Don't you hate it when your rubber falls out?" Why yes yes I do! LMAO
He should apply a transient kinetic stimulus.
A technical tap?
The anode cap to CRT go bad and arc causing dim, or arcing to frame and CRT won't turn on as a result. See spot where it arc over on side of frame. RTV over the anode cap usually fixes it. Just use clear RTV and let it cure for a day.
Once I bought a 30 years old scope (it was comlitely analog). But after few hours of work horizontal line disappeared from screen. Thankfully I had a manual and after some investigation found that problem was in CRT's drive output transistors (don't remember vertical or horizontal coil). But I was able to find broken transistors only when scope was switched on. Without powering it on transistors seemed normal.
Looking at the adjustments on the main board, it *does* look like you can run the CRT without the scope because it's a regular VGA monitor, with the 16-pin ribbon cable feeding video. VGA is nothing more than a set of analog R/G/B signals (which are probably mixed together on this mono screen) and a TTL-compatible pulse to trigger horizontal and vertical sync. That will take up 10 pins, with the remaining pins probably providing the power voltages required, it should be pretty easy to figure out which pin does what by scoping them, you'd need a high-bandwidth scope though, like the one you're trying to fix ;-)
Stoney3K actually, TDS series scopes from this years used to have a db-9 VGA output on rear panel. My TDS320 has it. VGA signal is monochrome.
This looks promising. the tube is good and so is the high voltage. This looks to be something that could be fixed.
Dave, check the deflection coils for resistance; and I would also suggest checking their control transistors/immediate circuits for good gates etc... should be able to do some off-line probing to possibly find the issue....
I was so gonna type in here be careful of that anode cause that thing hold some juice in for a long time. Cool video.
You need to find the adjustment pots and give them a turn while it's on and see if you can affect the picture in both directions or not. You also need to see if the screen pot (usually on the flyback) makes the screen brighter or not (be prepared to get a slight shock if the flyback is faulty). This will let you know if the problem is horizontal deflection, vertical deflection, or the flyback.
Query Please Twice. Not many scopes use magnetic deflection. Most I thought used electrostatic due to the faster speed. This scope use the magnetic cause it has some on screen display capabilities other than just the trace? Thank you.
I have been shocked trying to improve the convergence of crts in the day. Survived it. The problem just may be not at all in the crt module...
You showed us a high voltage probe adapter in the last video. Use it to check the screen voltage and horizontal, vertical waveforms.
My money is on a power supply problem...
Cheers,
- Eddy
You can run the driver board external to the chassis. Reconnect the ribbon cable, reconnect the CRT, and it should run. Of course, you have to be careful with positioning, but this will allow you to measure voltages and probe around. Check the linear regulator output first, then have a look at the 50V and 500V rails. My guess is the failure is in the linear regulator, or in the flyback transformer (or driver). If you have a good 50V and/or 500V rail, then the flyback driver and H-sync path is probably all good. You can still have a flyback failure on the CRT anode HV though.
Can you hook up a current probe to check for signs of activity. Especially on the deflection coils.
If the flyback supply is working and buzzing then it will probably be the high voltage transformer the culprit. It must be a very obtainable part. CRT devices needed this changed all the time for repair until they were obsoleted in the late 2000s
@Dave: could you please post a link to the forum thread you mentioned?
Yesssss !!!
Thanks for trying to fix it !
Please do a giveaway of this.
Make it open to everyone and I am sure just for once you could afford international shipping if its an overseas winner ;)
Where the hell can I find a magic dumpster like that??? Grrrrrrrr
Me too...
I think "dumpster" is code for all the crap he buys on ebay.
Is there a brightness knob. Maybe something is out of tolerance and made it dark.
Yes, there's a set of trim pots on the CRT driver board, and it wouldn't do any harm at all to try adjusting them to see what happens (if anything).
Or maybe the intensity, according to the manual it can go down to 20% close to off.
@@andyc7724 I've done that, nothing.
Hurry up with part 2!!!!
I wanna see Dave use mathematics for integration and/or implementation into a theoretical system and a bode-plot. Theory only and a whiteboard ofcourse 😎 challenge accepted?
Part 2?
Don't you just love it when there is a part one, obviously leaves you hanging, and a year later you can't find a part two?
yeah you just need a little monitor to cram into this thing and you're all done, but my god, did I just saw four big RISC processors?
Dave, did you forget the first rule of troubleshooting :)
Dave! Did you complete fixing this thing? I've searched the world over and haven't yet found part two. Us Covid-19 dodgers want to know.
Ooo goodie!
Why? Is it coming your way? That's convenient. He fixes & you flip it. What are friends for anyway? 8-)
The saga continues!
please don't give up on repairing the CRT but also please do the LCD mod
You do seem to have a much higher grade of dumpster than what we usually see around here... :)
Yeah true, our one just smells bad.
*Don't you hate it when your rubber fall's out*
My dad still says that to this day for the past 28 years, dunno what he means by that though.
If it weren’t cost prohibitive, send it off to Paul Carlson. He’d probably have the CRT up and running in 30 minutes.
LMAO @ 0:25
Yeah, I thought the boards in there looked a lot like the ones in myTDS744A ;)
Please repair it!
Crt board are very "reparable".
Do not put a rubbish lcd!
YESSSSSS.... I support your opinion highly too, forging history for ANTIQUES is just like killing someone.
Thanks Dave :)
Dangerous anode cap? It just gives you a shock, it won't kill you.
Agree, never heard of anyone being killed working on a tv, it's more dangerous to apply 220 vac to a 110 device.....
Okurka it’s true that it probably isn’t lethal, but there is still risk of nasty injuries, such as whacking your hand against a sharp object as it jumps wildly from the jolt.
Problem is you drop the crt and it implodes. Or breaks foot. These things give a helluva wallop
I actually met someone who was a specialist in fixing CRTs, and had a few high voltage shocks on these things. Damages to its motoneurons left him with a hand permanently shaking. How practical for soldering!
Seriously, never ever toys with CRT without discharging them. It's easy, it is nothing but a capacitor. So before unplugging anything, connect an alligator clip to a screwdriver, the other lead to the ground of the device, lift the skirt of the suction cup (you naughty!), blindly probing for the hole (this is getting pornographic) until the bad boy discharge (here we are).
Then you can disassemble everything. Some CRT have auto-discharge circuitry, some does not hold the charge for long, but anyway, never tick the dragon tail, better probe its hole before anything.
@@gerrymacdonald5435 Actually there has been lots of people killed working on older TV's since most of the picture tubes runs on 17KV to 32KV by using a EHT/flyback transformer which converts line level 120v/220v to 17KV - 32KV as required by the specific picture tube.
You need to be careful with the anode cap. Lick it to make sure it's discharged.
Was that a dad joke?
I can validate that an anode lead can knock a guy out. 5 minutes of my life I don't remember....
Hack the scope, make it a hackers scope. And put a Gotek floppy emulator in it. And a RPI to communicate via ethernet.
I love seeing mods, the more the better 😀
and make it run DOOM.
Yeah but it's 90's era Java based, if you already know it or want to learn it then awesome. I personally wouldn't want to go down that rabbit hole again unless I absolutely had to.
@@dangermaus42069 Wouldn't you do C or C++ then? It's from the 70s and 80s. Java and C++ are still some of the most used languages today.
@@zer0b0t yeah I decided to go down the C path, just far enough to get a LCD display and some sensors working on an arduino, that's been fun. So many gadgets, so little time.
4:20 😂
0:26 - that's what she said
Cool video but what is it and what's it for?
It's a multi channel oscilloscope - used for visualising electronic signals and waveforms
Please don't upgrade anything even for better performance, just keep it as is. If you could not or wish not to fix it anyway then resell it as is and get your commission and I will buy.... YOU PEOPLE DON"T LIKE ANTIQUES AT ALL !!!.
0:25 aaand demonetized