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GuruSantiago

TI Color Monitor problem. Looking for schematics.

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My TI color monitor just started to have a problem. The vertical linearity is way off, it seems like something overheated a few nights ago. 

 

I searched for a service manual and schematics, but I did not find one. Is there a schematic for this monitor anywhere? 

 

The Model is PHA4100A. The Chassis number is NMX-K6NC. The monitor was manufactured by Matsushita Electric Industrial Co. of Fukuoka Japan in 1983.

 

Thanks in advance.

 

GuruSantiago

 

 

 

 

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Don't have the schematics... been a while since I worked on that particular issue... if you are at all familiar with T.V. sections... Following the wires from the deflection yoke coils to their destinations can often be enough to locate the Vert. deflection section.... usually two transistors with heat sinks, driven by an I.C.. I'd probably start by checking the electrolytic capacitors near the I.C., replacing with tantalums as I go... also sometimes there is a v.lin. adjustment pot. or fixed resistor.

 

    P.S. Sorry, if I'm being presumptuous.:)

Edited by HOME AUTOMATION
punctuation
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It may be necessary to see if it's a vertical deflection IC or a simple vertical deflection circuit.  If it's an IC, it probably has integrated sawtooth generator feeding into a feedback circuit and then into the output amplifier.  The intent is to make sure the vertical deflection moves as commanded by sampling the actual output into the feedback part.  There are a few transistors, capacitors, and probably even a transformer involved.  So there are a few things to go wrong.

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If you have never worked inside a TV or CRT monitor before, I want to stress that there are voltages in there that can kill you.

 

I have found some of the best monitor troubleshooting info and help is on the arcade-museum.org forums.  The schematics for the TI monitor are probably going to be very hard to find.

 

You will probably get a lot of suggestions to do a cap-kit on the monitor, which I used to be an advocate of.  However, the last 3 monitors I did the cap-kit on, the new parts (caps, HOT, and various resistors) put too much stress on the older parts there were not replaced, and the result was a blown fly-back or killed other more obscure parts.  Even when a replacement fly-back was available, the new one would die very quickly.  It has been very frustrating because parts like the fly-back are very specific to the monitor, and finding replacements is sometimes impossible.  Trying to find a substitute would probably require an EE degree and in-depth understanding of the high-voltage section of CRTs (as well as the electrical specs on the CRT tube and coils).

 

Remember the CRT is 30 to 40 years old, and finding and replacing failed or aging components will not always fix the monitor, or keep it working for any period of time.  It is unfortunate for sure, and I don't think there are any companies remaining in the world that are actually making CRT monitors or parts for them.

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Oh yeah, not only do the mains and HV caps store juice... the screen grid in the CRT can make it act as a Leyden jar! ...get too close and, ZAP!!!:o ...I did this when I was seven.:lol:

 

I heard that when the Flyback or H OUT transistor blow repeatedly ...the high voltage clamping diode should be replaced.

 

I replaced a Sony Flyback on a large screen TV, with one from a similar model in the early 90's. The replacement part# was only off by one digit. After removing and comparing side-by-side... to the naked eye, all was the same... except for the coupling of one set of coils and the orientation of one leg. This required the cutting of two traces and cris-crossing jumper wires. After replacing a couple passive components... the screen dimentions were right. I did this "in the field" got paid $40, went home. A few days later I get a report that something's not right with the picture... they said that the letters were messed up and they couldn't read, when words were on the screen. I had a feeling what the problem might be... yes, the image was mirrored. I cut the wires to the horizontal yoke coil and reversed their connections. Problem solved ...not very profitable!:twisted: Lots of travel, time. Maybe I should have charged for the part.:grin:

Edited by HOME AUTOMATION
Hey... I didn't re-post!
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On 7/21/2019 at 10:02 PM, matthew180 said:

If you have never worked inside a TV or CRT monitor before, I want to stress that there are voltages in there that can kill you.

 

I have found some of the best monitor troubleshooting info and help is on the arcade-museum.org forums.  The schematics for the TI monitor are probably going to be very hard to find.

 

You will probably get a lot of suggestions to do a cap-kit on the monitor, which I used to be an advocate of.  However, the last 3 monitors I did the cap-kit on, the new parts (caps, HOT, and various resistors) put too much stress on the older parts there were not replaced, and the result was a blown fly-back or killed other more obscure parts.  Even when a replacement fly-back was available, the new one would die very quickly.  It has been very frustrating because parts like the fly-back are very specific to the monitor, and finding replacements is sometimes impossible.  Trying to find a substitute would probably require an EE degree and in-depth understanding of the high-voltage section of CRTs (as well as the electrical specs on the CRT tube and coils).

 

Remember the CRT is 30 to 40 years old, and finding and replacing failed or aging components will not always fix the monitor, or keep it working for any period of time.  It is unfortunate for sure, and I don't think there are any companies remaining in the world that are actually making CRT monitors or parts for them.

I agree with you 100%. Years ago, I repaired TV's and I know how parts that are degraded will fail when new and stronger componts are added.

 

My hope was to find the schematic before didding in. I already checked for a vertical linearity adjustment, but I didn't find one. The amount of dust is so much that I need to clean the monitor first before I make an attempt to a repair. I suspect that the problem is in the ramp generator for the verticle. maybe a bad resistor or cap used to linearize the ramp.

 

Thanks for your feedback. I agree on the no re-capping. Too many people latch on to that as a firs step. I have been in the industry long enough to know not to fix it it it isn'y broke.

 

GuruSantiago

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On 7/20/2019 at 6:01 PM, GDMike said:

I was just about to mention verticle sect. Spray with coolant..

It does this when it is cold, so the cool spray may not make a change. 

 

I have a friend that hit a Sony TV with some cool spray and it seemed to fix the issue, then he heard a loud pop and the TV died completely.

 

The best approach is always using a volt meeter and a scope to isolate the problem.

 

Thank You,

GuruSantiago

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I appreciate the feedback. I will continue my quest to find a schematic. If it is impossible, I will reverse engineer the vertical section and start troubleshooting  until I find the problem. I have seen and fixed this on TV's and Arcade Monitors in the past.

 

Thank You all,

 

GuruSantiago

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Hello

 

I have the exact same problem here with 1985 14' JVC monitor.

Picture stretched on top and collapsed on the bottom.

Hope you found how to fix your Matsushita :)

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On 7/18/2019 at 10:11 PM, GuruSantiago said:

My TI color monitor just started to have a problem. The vertical linearity is way off, it seems like something overheated a few nights ago. 

 

I searched for a service manual and schematics, but I did not find one. Is there a schematic for this monitor anywhere? 

 

The Model is PHA4100A. The Chassis number is NMX-K6NC. The monitor was manufactured by Matsushita Electric Industrial Co. of Fukuoka Japan in 1983.

 

Thanks in advance.

 

GuruSantiago

 

Realizing this is an old post, but I was able to dig up two models manufactured by them between 1980-83, a 14" and 19" complete with troubleshooting and schematics/parts listings.

I know it's a shot in the dark, but I'm hoping with technology as it was back then even if the first isn't your model, there should be good similarity since same manufacturer? ¯\_(ツ)_/¯

 

To widen the topic some, here's the resource that may help out somebody else with other monitors: https://www.mikesarcade.com/arcade/monitors.html

 

Doug

Matsushita14.pdf TM202G.pdf

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On 7/21/2019 at 10:02 PM, matthew180 said:

If you have never worked inside a TV or CRT monitor before, I want to stress that there are voltages in there that can kill you.

I recently worked on a Heathkit H19 terminal with a bad keyboard decoder chip, and it scared the shit out of me as I had to work in very close proximity to the coils and power supply to get to the chip. I'm still vertical, so that's good, but I have a very healthy respect for the kind of voltages floating around in there.

Incidentally, in case I have to get back inside the terminal again (shudder...), what' the best and safest way to discharge the capacitors? I hope it's not shorting them with a screwdriver!

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Best way is to use an insulated handle with an electrode that is connected to a ground wire that has a 100K resistor (1W would be best) in series with the path to ground.

Better than a screw driver would be a short piece of small plastic pipe with an electrode on the end. This would be better for playing with CRT circuits. Use a strong method to connect the lead to ground ie: a strong alligator clip or even screw it to the chassis if it makes you more confident.

 

After turning the unit off and removing AC cord, go around the circuit and touch the lethal sections with the special grounded tool.

Hold it on each HV point for a couple of seconds.  Be aware that capacitors will self re-charge a little.  This not a problem for 100V cap, but a 15,000V cap can still be dangerous when it self re-charges back to 1000V!!   We used to call this "air charging" but the real mechanism is some magic physics I would think.

 

You will also understand why we always worked on HV gear with one hand in our pocket.  No need to defib needlessly. :) 

 

It definitely focuses the attention.  When I was young I opened an old oscilloscope and reached over the chassis and contacted a 1.5Kv oil cap into my forearm.

I couldn't go near that thing for days.

 

 

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Some late models had a B+ chassis. Ouch! While newer models may have an insulated chassis.
I'm not a fan of this discharge to GND idea! In fact, I like the screwdriver idea better, though also problematic. Some capacitors might not be connected directly to GND. This could result in excessive I and V to other sensitive components. This could also result in reverse voltages across other components, possibly charging other capacitors as well... not magic! Finally, this may not discharge some capacitors.

 

The picture tube itself is often well insulated and can hold a formidable charge for long periods of time. Zap!

 

:ponder: Always! Think First!

 

:)

Edited by HOME AUTOMATION

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9 minutes ago, HOME AUTOMATION said:

Some late models had a B+ chassis. Ouch! While newer models may have an insulated chassis.
I'm not a fan of this discharge to GND idea! In fact, I like the screwdriver idea better, though also problematic. Some capacitors might not be connected directly to GND. This could result in excessive I and V to other sensitive components. This could also result in reverse voltages across other components, possibly charging other capacitors as well... not magic! Finally, this may not discharge some capacitors.

 

The picture tube itself is often well insulated and can hold a formidable charge for long periods of time. Zap!

 

:ponder: Always! Think First!

 

:)

Thinking is the best practice for sure.

When we worked on studio monitors we always grounded the CRT anode for the very reason you stated.

 

If you want faster discharge you can adjust the resistor value down to control the amount "snap" :)  you want to cause.

 

On the broadcast transmitters I worked on inside every rack was a "shorting hook" which was tied directly to ground.

It was a 2 foot plastic rod with a brass hook on the end that you would hang on a high voltage point and leave it there while you worked.

This was on top of the shorting points installed on all the rack doors that shorted B+ when you opened the door.

 

Now sometimes in the wee hours of the morning you might forget to remove the hook, close the cabinet and hit the power.

That was called a power supply overload detector and circuit breaker test. ;)

 

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I have a 10” Color Monitor that went crackle crackle fizz. I’m not interested in diving inside it. 
 

I have an idea to reuse the shell around a small LCD screen. For use with F18A. 
 

I’m still wary of disassembling the monitor to take out the electronics. 

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1 hour ago, FarmerPotato said:

I’m still wary of disassembling the monitor to take out the electronics. 

Plug it in for ten minutes.  That will make sure all of the energy is drained into the mains line.  Afterward, you should be able to safely scoop out its innards.  Also, make sure you are grounded while touching any exposed conductors and traces to safely pass trickle ohm charges into the earth.

 

THIS POSTER IS A SPIDER. DO NOT TRUST HIM!

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Maybe, just what the doctor ordered:🩺

 

After it went out of service...📺

 

I left it sideways, up on a shelf, near the heating system. When I finally pulled it down, it was working again!:cool:

Turned out... one of the boards was mounted sideways, all the electrolytic fluid had pooled-up on the sides of the condenser's cans.:roll:

 

   P.S. $20 service/storage charge.:grin:

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When being grounded, make absolutely sure you are grounded on the same hand you are using to reach inside. My old uncle who did TV repair his whole life advised that you should only ever reach in with one hand, to avoid getting current across the chest. But without actually discharging the high voltage, you do need to be really careful. It's up to you, but I wouldn't advise it myself if you are nervous about it.

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I always left alligator clip leads attached to HV CRT boards straight to ground and never had an issue pulling boards apart in my old TV CRT days.  Never used those resistor filled shorting probes. Shoot. I must a ripped 200 TVs apart in one night so that other techs could get to work in em..

I had a simple job. Lol

Edited by GDMike
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When I was but a wee sprout, I picked up a used TV from a garage sale and wheeled it home carefully balanced on the seat of my ten-speed. It was a big sucker, I think like 21", maybe a little larger.  It needed a little work and at that time in my life I was invincible and immortal. I was also pretty dumb, of course: not dumb enough to work on a TV while in the shower, but definitely smart enough to unplug it before working on it. Somehow while adjusting the guns, I dropped my screwdriver across some contacts having to do with the tube and the fly back, and fly back I did! Knocked me backward off my chair and the shock sent my arm upward, releasing the screwdriver and embedding it into the ceiling.

 

Hoo boy! Learned one hell of a lesson that day, but also got that thing adjusted perfectly. Pictures on the screen looked like they had been painted, no more lines or fuzziness.

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7 hours ago, OLD CS1 said:

When I was but a wee sprout, I picked up a used TV from a garage sale and wheeled it home carefully balanced on the seat of my ten-speed. It was a big sucker, I think like 21", maybe a little larger.  It needed a little work and at that time in my life I was invincible and immortal. I was also pretty dumb, of course: not dumb enough to work on a TV while in the shower, but definitely smart enough to unplug it before working on it. Somehow while adjusting the guns, I dropped my screwdriver across some contacts having to do with the tube and the fly back, and fly back I did! Knocked me backward off my chair and the shock sent my arm upward, releasing the screwdriver and embedding it into the ceiling.

 

Hoo boy! Learned one hell of a lesson that day, but also got that thing adjusted perfectly. Pictures on the screen looked like they had been painted, no more lines or fuzziness.

Now that's funny. That's also how you learn quite fast. Lol. Man, you didn't shrink, you didn't vanish from the earth. Amazing...

 

I did something stupid, so I'll even the field here. I had a laptop wide open looking for a problem, and of course it had to be running to troubleshoot the issue, and of course a screw I was holding dropped and hit the motherboard, bounced once and shorted the board, but unlike your monitor, my laptop never worked again, BUT I was blessed with 3 free laptops from an apartment manager..weeeelol..

 

Edited by GDMike
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