Hi! My First Post. Problem with 25" Monitor

Check around the neck board, most likely it will be the transistor, resistor or zener associated with that colour (blue) each colour has its own separate transistor and resistor. if they all test ok then it could be your Monitor and the blue gun has gone.

Hi Serviceit,

 

Thanks for the reply.

 

Are there any guides available about this neck board? I'm also conscious of the charge remaining that I need to be wary of.

 

I quite comfortable with electronics having done a degree in it...but also know when something is out of my skills. :)

Just have the power turn off and unplugged. The HV is under the suction cap on the monitor- there are lots of threads on that- just stick a screw diver under that cap and short to earth - done.

The transistors and the resistors are obvious on the neck board, one for each colour. Those are about 80% of the missing colour problem. If they are all ok then it is more than likely its the gun on the monitor that has gone faulty.

Its a terrible assumption on my half, but i'm assuming you have check the other obvious contenders- wiring from the jamma to chassis is all ok- jamma connection to the board all ok

I'll have to have a look this weekend when I have some time...

 

I saw another thread with a youtube video to ground/discharge so comfortable with that now.

 

I have a multimeter so checking resistance with be no probs. How can I check the transistors (this is going to sound sad, did my electronics engineering degree nearly 10 years ago...need a refresher)? Also, what's a zener?

 

I have a number of things to do for my neglected machine:

 

1) Replace suicide batteries in 3 CPS2 boards (don't use them much and has been over 4 years since last change). Trying to locate a place that sells Keystone Battery holders to make future jobs easier. I'm still not comfortable that people say that the boards have 20 mins to 1 hr capacitor charge to allow the batteries to be disconnected for that long.

 

2) Try and fix the monitor. If I'm not comfortable in doing this, I hope there's someone in Melbourne that could help? Also, I've heard that maybe TV repairmen can do a check?

A zener is a special diode that exhibits properties that make it suitable for use to clamp or regulate voltage.

 

[ame]http://en.wikipedia.org/wiki/Zener_diode[/ame]

 

 

You test transistors with the diode function of your multimeter and treat it as if it were 2 diodes in series.

 

http://www.elexp.com/t_test.htm

 

You do have to roughly know the type (NPN, PNP) and pinout (where the E, C and B are). If you get a dead short, it'd be a problem. You do get the other channels on the neck board to swap around and test if it's the real problem though, so it's a good thing (sorta like repairing stereo amps).

 

Monitor: yeah I don't see why a good TV repairman can't fix an arcade monitor, it's about the same except easier probably. There's a guy here (Jomac), that everyone'll recommend. Not too sure how far away he is from you though. If you can isolate the problem down to say the chassis (the 'board' for the monitor, instead of the tube), you can probably send that to him to get it fixed, or have him send you a replacement.

 

If you are not squeamish around HV, and know/can take precautions while working on it, I say give it a go. Fixing my own stuff always gives me the warm fuzzy feeling. :lol

serviceit, wiring from jamma to board and jamma to chassis looks ok. I haven't checked it though via multimeter. Also, the wiring from board to jamma goes into a metal box with test, service and power switch at the front so it's not readily accessible. Checked all plugs on top of this metal box and chassis to make sure they're in properly.

 

Just some more info, this problems happens with all my cps1 and cps2 boards.

 

li_gangyi and serviceit, if the neck board is what's at the bottom of the crt, then I'm probably not game enough to take it off and check.

 

li_ganyi, i remember what a zener was overnight...it was so funny...recalling long lost distant memories of lectures...

 

Maybe there's someone in Melbourne that can help?

 

I've also attached images of the test screen. The green doesn't look that green and the white is not that white (maybe because I'm colour blind...)...even so...

After finding out the price to get it fixed professionally, I've now got more enthusiasm for a fix myself. They also said it most likely won't be the gun as it's usually the red that goes first on 25" monitors.

 

In the first picture above, to the right I understand now is the chassis. Is the neck board the small board at the bottom of the crt? If so, there's not too many components to check it seems...

After finding out the price to get it fixed professionally, I've now got more enthusiasm for a fix myself. They also said it most likely won't be the gun as it's usually the red that goes first on 25" monitors.

 

In the first picture above, to the right I understand now is the chassis. Is the neck board the small board at the bottom of the crt? If so, there's not too many components to check it seems...

 

Yep, that is the neck board :023:

 

Matthew

Project Blue!!!

 

Thanks for everyone's help so far... Now I'm getting excited about fixing this myself.

 

If anyone lives close to or in the Whitehorse area and doesn't mind giving a hand...it would be great.

 

Ok, these are some questions to get me started:

 

1) I can't see the suction cap looking at the monitor from the front, I'm assuming it's on the other side from the rear?

 

2) To ground/discharge, I need to get it to earth. I read some people connect it to the earth terminal of the power plug. Doesn't this not then get the charge to earth as it's not plugged in?

 

3) If I put the alligator clip to the metal frame of the cabinet, does the unpowered power plug need to be plugged in so it can earth?

 

4) If the monitor is earthed/discharged, I'm assuming the whole system is also earthed discharged, eg. the chassis.

 

5) How do you get the neck board off the crt? Looks stuck on?

 

6) Could there be something wrong with the chassis board contributing to the blue colour loss? I now know why the white is off...because I've loss the blue colour to not contribute to the white...

 

7) Once I get the neck board off...

a) How do I know what the resistances are suppose to be? Read the old fashion way based on lines or are they standard where there's a schematic available? If you guys say read the lines...it's going to bring bad memories from uni...being colour blind and all... Bad memories meaning depending on sisters to read the colours...

b) Will the transistors have codes on them so I can then find out whether they are NPN or PNP?

c) The zener diodes... How would I know what the cutoff voltages are suppose to be?

 

8) Are there any guides, fix logs that go through this neck board check? Are there more guides like the one the li_ganyi provided to help understand how to check the diodes and transistors?

 

9) I understand the process of check the resistors and zeners would require at least removing one leg from the board? The transistors would be easier if they were removed altogether?

 

Sorry for all the questions...especially ones that sound stupid. If there are threads already available about these questions, please feel free to point me in the right direction. I did a check and couldn't find any aside from the monitor discharge ones. Thanks in advance!!!

OK,

Have you checked the pcb? Are you able to swap another into it?

 

If you do suspect the neck board transistors, swap 2 over and see if the problem follows

Hi Prof,

 

Luckily I have a few CPS2 boards and one CPS1 board to test and it happens with them all. So luckily, I can discount one thing...

first things first - if you are not confident about doing don't.

The Hv suction cap is at the rear of the monitor and all i do is simply place a long blade screw driver under the cap and short the steel rod to the metal frame.

the neck board simply pulls out.

The values are irrelevant at this stage all you are looking for is a variance between them, the faulty one will stand out. You are measuring the resistors with the meter set to ohms, the transistors i just use the meter set to diode and measure between pins 1-2 and 2-3 and 1-3 on each transistor.

Remember each colour has its own driver transistor, resistor and depending on the chassis zener.

But before doing all that, check the obvious, dry joints or cracks on the circuit board.

Even clean the pins on the tube and clean the sockets on the neck board going to the tube.

 

PS Joey is very cheap- or i think so at least- so if you are not up to send him a PM and get a price- you will be suprised.

serviceit, thanks for your reply. definitely won't do anything that i'm not comfortable with. I looked up Joey on the members list and couldn't find him. Is Joey under a different name?

 

One more question, a 10th to add to my overall list:

 

10) I'm assuming the jamma board is in the metal box as there are wires that go from the PCB into into and from it to the chassis. Anything in particular I need to do to get into the metal box to get to the jamma board to check wiring?

 

 

Ignore question about Joey, thanks for the pointer in my other thread!

 

Wow, I read the Jomac thread which has one about what he does and the service he's given...and I have to say....WOW!!!

 

Serviceit, should I just wait for Joey to reply to my PM to see what he wants me to provide him?

 

Or do you have a suggestion as to what boards to send him?

 

You all have been so helpful...so glad I came across this forum.

Edited April 14, 2009 by noisuf
Auto Merged Double Post.

the metal box is more the likely the power supply

 

Jamma is a standard for the edge connector on the pcb itself

 

You will need to send him the chassis and the neckboard ( they are connected anyway) after discharging the monitor

jamma is the connection from your game board-

http://members.iinet.net.au/~getderrick/JammaHarnessLabelsAZcorrectedFINAL2.jpg

and each colour has a seperate lead going to the chassis.

if you send it to Joey all that he needs is the Chassis- Joey can explain if you are not sure.

Thanks everyone for your help. I'll let you know how it goes!

I've PM'd Joey and provided him with more pics of my chassis, neck board and monitor.

 

http://www.aussiearcade.com/showthread.php?p=279828#post279828

Got a uni chassis from Joey, just installed. Looks beautiful.

 

Will be posting pics over weekend and another addition to the "Joey is tops" thread!!!