Playing blind with glow

[jthunderbird]

I have read every thread I can on this forum looking for a problem similar to mine. Though there are plenty of dead monitor threads, nearly none of them have the same symptoms as mine, notably the glowing neck area.

The arcade is a NFL Blitz 2k Gold and NBA Showtime machine (the exact machine Ive looked for the past couple years). Everything looks brand spanking new, even came with the alternate marquee displays and user manuals. It boots up seemingly fine and makes noise. You can press buttons and things happen, just no picture.

I have messed with the setting on the flyback as well as ensuring none of the brightness/contrast were set all the way down. Not sure where all to hook up the MM because the internals of this look different than most post (newer machine maybe). It is getting 119v to the AC-IN connector on the chassis board. There is no noise whatsoever when I attempt to discharge the monitor, even right after shutting it off...

Previous owner said it worked fine inside and never had any issues until they tried to fire it up a few weeks after it had been sitting in their garage. I get nothing, absolutely nothing from the screen. I will try completely dark tonight, but I didnt notice anything at all. It still makes the crackling CRT noise when going on or off. It is a k7500 series (exact model escapes me at the moment).

Anyone have any ideas other than the MM or full k7500 overhaul kit?

[jthunderbird]

The last picture shows a small green bolt in the chassis (bottom left corner) that has a tab like it should have a ground attached to it. Is this a possible reason I had an issue discharging? I attempted to discharge the monitor using both the chassis frame and the bare wire going around the monitor (earth wire I think someone called it).

Any help is greatly appreciated...

[grantspain]

so you had tube heaters but did you have HT,you can tell that by feeling if there is any static on screen or you can hear the HT when the monitor fires up

[jthunderbird]

That I am not sure of... not sure what it would sound like. I do hear the static monitor sound but I havent actually felt for static on the front of the monitor. I will test that just as soon as I get home from work today.

Open to any other ideas as well... its torturous to be able to hear and control one of my nostalgic favorite games of all time and not be able to see it.

[jthunderbird]

Ok just got home and removed the front glass. Powered it up and gave it a minute... no static that I could tell and if there was, it was very minimal.

So no static on the front and no crack from trying to discharge the monitor leads me to believe the flyback is the problem. The anode was a little looser than I expected on the back of the monitor but there is no leakage or anything that I can tell.

If someone can point me to how to test the flyback or any next step... thatd be awesome... I am out of ideas and pretty bummed I cant play this thing.

EDIT** There IS static on the screen... just needed longer than the minute I gave it the 1st time haha. Turned it off after letting it run for 15 minutes or so and there was plenty of static coming from the front of the screen... more lost than before now.

[grantspain]

check for bad solder joints

[jthunderbird]

check for bad solder joints

I will pull the chassis and neck board when I get home tonight if I dont get in too late... anywhere specific I should check? Thanks for the assistance, I really do appreciate any help with this.

[grantspain]

on all chassis the places to star looking are connectors or large components such as transformers,on your particular chassis i would also check the crt socket on the neck card
did you say you had tube heaters?
if you have HT and tube heaters then in general the chassis is running,if the screen volts control on the flyback does not affect the brightness then check the thinner of the two wires going to the neck card
it is possible the flyback could be at fault

[jthunderbird]

on all chassis the places to star looking are connectors or large components such as transformers,on your particular chassis i would also check the crt socket on the neck card
did you say you had tube heaters?
if you have HT and tube heaters then in general the chassis is running,if the screen volts control on the flyback does not affect the brightness then check the thinner of the two wires going to the neck card
it is possible the flyback could be at fault

The tube on the neck glows, not entirely sure what you mean by the HT (sorry, Ive read a ton, but some things still allude me). I have class tonight but will try and pull the chassis when I get home... maybe snap some more clear pictures once out of the cab. Thanks

[grantspain]

neck glow means tubes heaters,HT is the high voltage that is static sound you hear-if you have both the chassis is running

check your screen volts cable to the neck card,it may have broken off

[jthunderbird]

neck glow means tubes heaters,HT is the high voltage that is static sound you hear-if you have both the chassis is running

check your screen volts cable to the neck card,it may have broken off

Theres a white (maybe greyish) and red wire that connect to either side of the tube on the neck board. I will look around and see if anything looks like it is missing.

[grantspain]

the thicker of the two wires is the focus line,the thinner is the screens volts-if the screen volts wire was broken or its circuit open then that would cause the issue you describe

[jthunderbird]

Hmmm.... well my neck board had 3 single wires going to it. A white (greyish) going to the neck hole tube slot thingy (excuse my ignorance please), a black wire going to the right of the tube (black arrow) and the red wire going to the left (red arrow).

The grey one was thicker while read and black were the same. The black went straight to the "earth" wire wrapped around the monitor. The grey and red wires went to the flyback and tucked kind of underneath it. Since the red is the thinner of those two, I checked it out.

It was glued in place so I broke the glue and pulled it. Looked fine, wire looked fine, seemed to be making a connection so I reinstalled and nothing changed. Because it is kind of tucked under the flyback as far as I can tell, I cant check out the other side. Is there a way to test that wire with a multimeter?

ASLO: The second pick is the back of the neck board. Solders looked fine but there were a couple brownish spots on the back (none from capacitors, looked like transistors I think). The brownish spots are not as bad as they look in the pic... it basically looks like small spots of dried soda or something, the solders still look solid as far as I can tell.

[grantspain]

tried the screen volts adjustment yet?

[Sarver Systems]

This is not related to the issue at hand, but pertains to your monitor.

On the neckboard, there are 3 transistors with little metal heatsinks on them.

Be SUPER careful not to bump those.

They get VERY hot, so hot in fact that the board will turn black near them.

From the heating and cooling, the solder weakens in that area, and the solder traces come loose.

I've had 3 of this monitor fail at those transistors, all needing traces rebuilt.

The transistors drive the color guns. If you're missing a color, check those first.

About the issue you're having...this is going to sound really stupid, but it wasn't mentioned i your post or any of the following troublshooting replies, but did you make sure your signal harness was plugged in? The R-G-B-Y-W harness.

It sounds to me like the monitor is working fine, its not given anything to display.

In a darkened room, do you see glow on the screen itself? Any faint image at all?

Do you have another monitor you could plug into the game to make sure its not the game board?

[jthunderbird]

I adjusted the B+ pot on the chassis board but it made no difference, not sure about the monitor voltage.

The RGBYW harness I am not sure... Can you make out where it goes on the pictures? I am fairly certain everything is plugged in correctly. I do not think the monitor is working. I have turned it on in a completely dark room and tried to cover the marquee light as best I can and couldnt really see any glow and definitely no faint images.

There is a TV repair guy who makes $15 house calls in my area and I think I am going to have him come over today. Even if I hand the job off to him, I will certainly learn what he does to fix it and even watch him troubleshoot if he will let me.

[Sarver Systems]

I couldnt find it in any of your pics, thats one of the reasons I mentioned it.

Can you take more pics at other angles?

You'll know which one it is because there's really only 2 wires that come from the monitor to the outside world. Power and signal.

The power wire is the (usually) black and white or sometimes brown-green-blue.

THe signal wires is a smaller harness of 5 or 6 wires. Red-green-blue-black and a yellow and/or white.

[jthunderbird]

As far as the monitor wires, where do they go into the monitor at? There are 2 or 3 wires that go into the the yolk area (where the tube plugs into). I did pull the cap off and I believe there were two wires attached (blue and red).

Also in the picture, the yellow is what I believe you are referring to for the rgbyw cable and the red arrow is the grey cable that runs from the chassis to the neckboard... I have checked, rechecked and reseated those connections.

[Sarver Systems]

You're looking for this:

[jthunderbird]

I don't see that specific connector.

So I handed it off to a TV repair guy who has 200 years experience... whatever, he felt confident he would fix it but called today and said its something with the neck board that cant be fixed because the part is not in his parts list.

Because I dont really know anyone local who can help, I think I am just going to replace it with an ebay order. There are a couple listings for whole chassis for around $120... my question is, how interchangeable are chassis? Mine is a 25K7501, will a 25K7191 chassis go in there and connect right up?

[ed12]

i c it clearly in your #3 pic
it is looking from the back of the board to the right hand side
pin's out
from bottom to front of board
bottom =r
next=g
next=blue
next =grond
next=blank
next=sync
next=sync

the 3 wire's u refer to are your foucs and screen and ground
ground is black
red=foucs
white=screen

if u fire it up and here a click and get neck glow
u can be perty much asursed it is running

the neckboard chip is a mm and or lm video proceser,very common chip

ed

[jthunderbird]

Pin is out? I have looked pretty extensively at all the connections, would think I would have seen a pin out. Can you be more specific?

[ed12]

on the right of picture #3 i see a header with 2 yellow wire's on it
look at it carefuly and see if on the board top or bottom is printed r,g,b

ed

[lilshawn]

I adjusted the B+ pot on the chassis board but it made no difference, not sure about the monitor voltage.

eeeek! that's a good way to blow stuff up. PUT IT BACK EXACTLY HOW IT WAS.

you can't go willy nilly tweaking adjustment all over hells half acre. That's a good way to end up with a chassis that's deader than dead and needs 60 parts replaced on it to get working again because it's been blasted with 300 volts on the B+.

FIRST BEFORE YOU DO ANYTHING:

find a little metal post or pin that is labeled TP202 (B+ test point) connect the positive lead of a voltmeter there and attach the black lead to the frame of the monitor. when powered on, it should read somewhere around 117v DC... wires with alligator clips on them really help with this. if the AC plug comes in on the bottom left side, TP202 is in the middle of the board to the right of the "S" shaped heatsink just in front of a big capacitor.

you need to make sure the B+ is not all messed up set your meter to read 200V (or more)

If it's gone (0 volts) there is a short circuit issue someplace or it's gone into shutdown. watch as you power up...is it coming on then shutting off? xray protection kicking in turn down B+) is it dead? check for voltage on either side of L100. if none, unsolder and lift one side of L100 and recheck...if none SMPS may be faulty. you'll have to try loading it with a lightbulb if this is the case...

if it's low (60 volts or under or going up and down and up and down) something is dragging it down, likely the B+ filter cap. (C107?) SMPS would likely be kicking it off and on trying to start up. check for shorted HOT.

if it's high something has gone open and it's just freewheeling. Likely bad solder joint on the flyback or HOT transistor. (i'd still turn it down to ~117v at this point till you can find the fault and fix the voltage later)

you need to systematically go through each part of the board and ensure it works first. finding out what works will eventually show you what is not. you've basically made yourself 10x the amount of work by pissing around with things since now we don't know if things are as they should be here or there because the voltages are all going to be screwed up now. 

[ed12]

i missed that point shawn thk-u very much,this may end beening a bag of snake's
so bear with the thread,we can get the @ through it...
chk e-me

ed

[jthunderbird]

Ok well looks like I may have dorked something up but we will see. Doesnt seem to be acting any differently. I will do the B+ voltage test this evening and reply here. Worst case scenario, I will just drop the cash and buy another chassis assembly.

I am trying to keep this cheap, but this isnt a flip for me or anything... just want to be able to play the game.

[jthunderbird]

Also, forgot to mention another symptom. The monitor repair guy pointed out that these three transistors (? I think) were super hot after running for a couple minutes though he doesnt know why.

He is returning the neck board to me today and from what I could understand, he still is unsure... any ideas?

[ed12]

they tend to run hot
as they are your r,g,b gun drive output's

ed

[lilshawn]

yeah, that whole area of the board (resistors and transistors) run pretty hot. it often causes the board to turn dark, even black. the copper foil often delaminates where the transistors attach on if you bump them. be careful with them, it's easy to bend them and push the leg through, tear off the pad, and rip the foil trace from it. and end up with a dead color.

[jthunderbird]

Ok, so I tested the TP202 B+ post and it was at 122 so I dialed it down a teeny bit down to 118.0.

Monitor repair guy brought my neck board back and said the problem was the IC on the neck board... the solder joints all look fine, anything else to look for in regards to the IC to maybe verify what he told me?

[grantspain]

rare but seen it when these ic fail you get absolutely nothing on screen-not even anything with screen volts
only way to prove is to swap the ic,solder braid time-not solder sucker

[lilshawn]

good with the B+. once we get a picture on the tube i'll tell you how to adjust it to where it's supposed to be.

if the transistors check out okay, it may very well be the IC. It's a video amplifier IC.

it takes the low voltage video signal from the game (typically >5 volts) and boosts it up to drive the transistors that switch the high voltage to the color guns.

Before you go much further though...

You want to get the monitor running again with everything connected, then adjust the "Screen" control on the flyback up to see if the screen turns brighter... kinda like this:



 if your monitor won't do this, you need to look at why.

the screen control cranks up the high voltage applied to the tube to pull more electrons to the screen. this results in the picture above. this is completely independant from the video drive and will let you know if the tube is getting enough juice or if you have a G2 voltage issue.

[jthunderbird]

Ok... fired it up and fooled around with the screen knob on the flyback... no difference I could tell except this time, it is really dark in the room and I could actually see extremely faint signs of life. Could possibly even make out little football players at some points.

I messed with all the brightness/contrast/etc settings and best I could manage was basically what I had... VERY faint and not entire picture. Does that mean cap kit and flyback?

[ed12]

of the 2 controls on the flyback
1=screen
1=foucs
u want the screen control,to reflect what shawn posted to u
if it does not do this ?
then u have low 160v from the flyback,or your tube has gone south,
a faint shadow glow means u are getting some kind of high volt's
if the tube neck is not glowing red at the end by the socket ?
this would point me to a open resistor and or crappy cap's or both
volt's chk is in order here

ed

[jthunderbird]

How do I check voltages for the flyback? Mostly I have read that the B+ is the common check for that (at least I think thats what I have read).

There is glow in the neck tube
119 at the input connector
118 at the B+ TP
EXTREMELY faint image
Flyback settings (screen and focus) have no effect I can see
Also noticed I get a kind of burn smell when its fired up (smells like its coming from those super hot resistors/heatsinks from the neck board but not sure).

I do have a 25" Phlips monitor in my MK2 machine... the neck yolk plug looks like it would hook right up. Could this monitor work with my board or vice versa? Could help rule out the monitor.

[ed12]

i would stop right now
call this 200 ear old guy and see if he has a tube rejanator
if he dose ?,ask him to come over and chk the emmision's of each gun r,g,b
thhey must be in the 75% or greater range
if not time to ditch the tube,DO NOT throw out the yoke,purity ring's
as u need it for the other tube u talk about..and btw without sounding
snoutty,the yoke part is a alot more involded then u would expect...
but i would do the tube test first..
next do a visuial and see if there is a open/burnt resster right off of the flyback
these will be on the top side of the monitor chassic
also if i rember there is a note in your answer's about a diode that goes south on u
so u will need to ref. back to the schmeatic
and find which winding's of the hot do what..
u are looking for about 160vdc at the neckboard >drive voltage for the output's<
if it is not there ? then that will be 1 of your problem's

ed

[lilshawn]

sounds bad.

check R310, R823, R811, failing that... the flyback might just be toasted.

still some other things you can check though.

[jthunderbird]

Ok I just researched how to check resistors and will do that hopefully tonight (depending on if anyone comes over for football and steals my attention). Worst case, I am leaving early from work tomorrow and will check them out (soon as I locate them).

Thanks again for all the help... I was actually able to fix the red color issue on my other arcade because of the second hand knowledge gained while troubleshooting this guy. Been pretty fun so far, just cant wait til Blitz powers up for the first time.

[jthunderbird]

So a little update...

I ordered a flyback and cap kit. Installed the new flyback today. Got everything hooked back up and zero difference... zero.

Going to do the cap kit tomorrow... but I really really thought with the new flyback, I would at least be able to get the screen to show an image with the screen control on the flyback... but nothing. Also tried a couple different neck boards with no change as well.

Anyone have any other ideas on what could cause almost no picture at all? Glow looks fine, plenty of static, sounds perfectly normal starting up. The hell is going on? I found a local repair shop here but he said I was looking at $250 starting only with knowing the name of the game and that the screen showed nothing... little more than I wanted to spend.

So disappointing.

[mgb]

Hello,
  Just a couple of thoughts. Forgive me if I ask something that you've already stated but just to get all the details straight.

Has the monitor ever worked for you?
So you have neck glow and static, right?

If you turn the screen knob up high, do you get white raster lines?

How does the Hirizontal width coil look, is it broken.

Do you know that your video to the monitor is good?
You should try connecting a cheap jamma board to the monitor.
You can find some for real cheap, or maybe you're around someone here that lend you one.

When you do the cap kit, try resoldering joints, cold solder joints are very common.

Make sure any pots on the neck board (color gain, cutoff) are adjusted half way