Nintendo Monitor 19" Sanyo 20EZ - Green

postmortem01

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The upper monitor in my Punchout is green in color. I'm not much of an electronics guy so determining the problem is difficult. I can't adjust out the green. I've done the typical cap kit on the monitor but the problem remains. Does anyone know other possible problems that might be causing this?

Resistors? Transistors?

Thanks guys.
 
Is the video going thru an inverter board (on the metal case over the flyback) on the upper screen? I've seen bad pots on those cause issues like that.

- Mike
 
I have the same exact problem with the bottom monitor on my play choice. Wondering if anyone figured this out. I haven't done a cap kit to it yet but I was going to put an order in at therealbobroberts and I thought maybe I could order some other parts just in case that could be causing this...since snail mail takes so long.
 
could be the transistor or it could be the tube.

either way a cap kit is needed and if the problem persists swap the neck board transistor to see if the problem moves to another color.

Peace
Buffett
 
thanks for the help ...you're right from everything I've read including the 20ez trouble shoot guide it says it's transistors in the neck board and upon physical inspection at least 2 look all burnt and the solder is blackish. I'll wait for those cap kits to come in before I do anything.
 
ok so my update is I did a cap kit. still same green screen. I checked all three transistors on the neck board and they are good. One thing I noticed is theres three resistors on the neck board that look like they got too hot and the solder is dark grey almost black. Has anyone ever had a similar problem to this and could this cause a green screen. the resistors are R261,R257 and R253 .
 
new updates. I removed the three resistors and tested them all. They were all bad and one of them wasn't even the proper resistor which should have been there. Replaced all of them. Two of the resistors had solder pads that started lifting. Probably because they got so hot. So I put a jumper wire to assure proper connection with the next point. Tested the monitor after this and found no change still just green. Start looking a little closer at everything and followed back the wires on the neckboard which go to the flyback and notice the purple one wasn't attached. The ones that are wound around the pins. I soldered it back in place.( not sure if that's ok but I couldn't rewind the wire back on the pin.) I also tested the B+ voltage and it was very high so I brought it back down to 108 volts. Tested again after this and still no change. So I'm not sure where to go next. Maybe check everything in the circuit which had the burnt out resistors? Could the flyback have be damaged and could that cause a green screen? Thanks in advance for any help

or one more thing to add. I have a spare yoke off of another sanyo 20ez it had bad burn in but I assume the yoke is still good. Do you think it would be worth the trouble to try swapping them to see if that's the problem. I just don't want to do to much to this monitor and create more problems.
 
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new updates. I removed the three resistors and tested them all. They were all bad and one of them wasn't even the proper resistor which should have been there. Replaced all of them. Two of the resistors had solder pads that started lifting. Probably because they got so hot. So I put a jumper wire to assure proper connection with the next point. Tested the monitor after this and found no change still just green. Start looking a little closer at everything and followed back the wires on the neckboard which go to the flyback and notice the purple one wasn't attached. The ones that are wound around the pins. I soldered it back in place.( not sure if that's ok but I couldn't rewind the wire back on the pin.) I also tested the B+ voltage and it was very high so I brought it back down to 108 volts. Tested again after this and still no change. So I'm not sure where to go next. Maybe check everything in the circuit which had the burnt out resistors? Could the flyback have be damaged and could that cause a green screen? Thanks in advance for any help

or one more thing to add. I have a spare yoke off of another sanyo 20ez it had bad burn in but I assume the yoke is still good. Do you think it would be worth the trouble to try swapping them to see if that's the problem. I just don't want to do to much to this monitor and create more problems.


No Not Flyback or yoke..

The tube could be the only issue here..

Test the emission on the tube..

Check the voltage at the base of each transistor TR251, 52, 53

to see if you have RGB drive from the Buffer transistors on the main board.

I usally check all the voltages on each transistor and compare between them.

An age tube will over heat the large resistors and poor filtering from C471 and C472

and damage the Video output transistors and may open a emitter resistor need

to check the ohms on each video transistor the 180 ohms make sure they are good.

Some case's all green picture with no video is a shorted green gun

a all green picture with video is a issue with driver/output stages.

If you turn up your red and blue do they seem to work ok??

http://www.arcade-museum.com/manuals-monitors/Sanyo_20EZV_(R-C)_Rev2_Schematics.pdf
 
I have the same problem but the reason mine is green is because the red is completely MIA. Luckily it's only the top monitor. Been too lazy to cap it.
 
are you going through an inverter board? I just spent like 5 hours at least trying to figure out why mine was green even after a cap kit. Stupid pots on the inverter boards seemed to be bad... after 5 hours of messing with it I found it.. but it's not needed so you can quickly remove that from the equation simply by as plugging directory into the monitor chassis rather than daisy chaining the inverter to the chassis.

-brian
 
Well I tested the voltage to the transistors on the neckboard at the base they where all getting about 10.9 volts. I also tried omitting the inverter board from the equation. Thanks for the idea. Unfortunately that wasn't it either. Wish it could have been that easy. I'll still keep trying some other transistors and tracing them back. As far as checking the emissions of the tube I guess I would need special equipment for that?
 
Odds are you RGB drive to each transistor..

If I mention a part its because I want to know

what its doing? did you find the 180 ohm resistors?

Very well could be the tube..

The cathodes can damage the video circuits

and over heat the transistor and video B+ resistors

over a period of time

and the emitter resistors..

If you short the cathode to ground for just a second

you should get that primary color flash??

if not the cathode of each color is weak or missing

Very common to have GK or RK or BK silk screened on the neck board

or see schematic..or follow the trace to each collector of each video amp transistors

try all three and compare the results..if you dont have a crt tester.

With all video transistors you should have a all blue or red or green

raster when you turn your drive pot all the way up to see if you have the color.
 
ok I found the 180ohm resistors on the neckboard. 5 in total all checked out good. One thing I noticed is I checked the voltage at the collector on all three neckboard transistors. tr251,252,253 and 251 and 252 which are red and blue my missing colours have 40 volts passing through but tr253 for green is at 48 volts. I also checked the drive transistors they where all the same voltage going through the collectors. I'm still trying to figure out where the cathode points to short out for a second are. I'm not exactly sure what you mean there. Thanks for all your help so far. I'm really learning a lot. Still a newbie but willing to learn. Also I bought a crt tester/ rejuv off ebay last night so if I hopefully in a week I'll get it and try testing the emissions.
 
Ok, you will need to wait for the Video Display Tester

or rejuvenator or CRT tester..

There are many types of leakage or shorts that could happen

with the cathodes, heaters..G1 Etc.

The Video B+ comes from the flyback and goes to all three of those

high watt resistors and off each resistor it goes to each collector and the cathodes

are the load for each drive transistor thru the large resistors.

In a sence the resistors/transistors will take current and from our point of view we will

see the high watt resistors over heat and often discolor and or increase in resistance

and even open up.. they should never be over heated to where the color codes

are missing.. they only fail because the circuit is trying to control the current thru

each cathode so if the are damaged its because the cathodes are pulling down the

Video B+ meaning that if you removed the cathodes or disconnected the pins

on the crt socket you should see the dc at the collectors depending which RK,BK,GK

you just removed the dc should jump up very close to the Video B+

Depending which cathode or two has the issue of a short of cathode to cathode

leakage it may act differently with the test.

I would hold off untill you have the VDT in front of you, thinking about the

the symptom you should notice that the green should test better then the others

unless you have a leakage between the heater and the green gun..

when that happens it is over driving the green cathode because of the H-GK

but not enough to make the green so predominant that you cant see video in it.

and should look at this first, and test the red and blue then ofcoarse Rejuv.

this way you can relate to your visual symptom.. dont just start Rejuvenating

right away, this way you can learn from what you aready know, i find it important

to relate to the symptom at all times!

You may run into heater to green cathode leakage and that the red and blue

or very weak in emission over all..

since the heater to cathode or heater to grid or cathode to cathode your

testing may be different and can understand whats going on inside the tube.

the resitors and transistors will all take the heat from the tube so it will give you

an idea where the problem is just from who's hotter then it next part..


I can tell the transistor were not shorted or the emitter resistors would have

been open or overheated because it would have put the video b+ to the emitters..

The transistors thru the whole ordeal can become leaky and still need to be changed

even if it was just the tube that was the big issue..

Odds are if you removed your RGB signal cable you would have a greenish raster.

Ofcoarse this is just my take on this repair and may vary depending what you find.

And if i'm wrong then never mind..Smile
 
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Ok so I have a pretty sad update so far and am not sure whether to give up. I got my heathkit only to find out it doesn't come with a cr23 adapter. Ha stupid me. So I got the parts and made one myself. Afer double and triple checking I'm sure it's wired correctly according to diagrams and threads from this site. So I'm using this thing and right of the bat it shows green in a good range and the other two colours not good. So I cleaned and rejuved and very little difference in the range test on the rejuvenator. I'm not sure about the voltage it's putting out. When I use the clean setting it says turn up the voltage till you get in the range of 3-5 but it will only go to 2 with the voltage maxed out. Then with the rejuve it says turn the voltage up until it's at 8.5 in the meter and only one colour will go up that high with the heater voltage maxed out. I've tried a few times now and I've gotten the blue to show up when I hook up the monitor..just faintly though. I also had the red show up a little too. But I can't seem to get those values ( gun current ) up around 5 on all of them. If I try again it sometimes gets better sometimes worse. Does anyone no how to check the output voltage on the heathkit. Maybe it's not putting out enough juice. Or maybe the piece of crap tube is garbage.
 
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