Monitor Chassis Repair - what to do / easy fix?

[Superully]

ok, the monitor on my wizard of wor has stopped working ! game plays blind, but absolutely nothing on the screen. when i power up the game, i can hear the static charge / crackle of high voltage, but that's it, the screen remains dark! chassis type is G07 CBO.

i did some digging on the KLOV forum, because this seems quite a common problem and the guys over there recommend replacing stuff like the flyback, the hot, width coils, caps etc! bob roberts carries different kits for that:

Go7 Repair Kit: http://www.therealbobroberts.net/g07repair.jpg

GO7 Super Repair Kit: http://www.therealbobroberts.net/g07super.jpg

Go7 Deluxe Repair Kit: http://www.therealbobroberts.net/g07deluxe.jpg

first of all, i have no idea which ones of those might fix my problem and second, i have never done something like this before. is this something an electro-noob can do or should i just get a replacement chassis? i could get one for 80 dollars shipped. how are the chances that one of those repair kits will solve my monitor problem?

i need some input, guys! 

[Etienne MacGyver]

IMHO; for people that do not have the electrical skills , or practice, i would say 80$ is a good deal, no soldering, just plug and pray.

especially with the current euro - dollar rate....  it will be € 60,-  thats not worth the trouble of a kit that maybe don't fix your problem..

on the other hand , it will give you some nice electrical practice with a kit 

[level42]

If you hear static/charge then it sounds to me your flyback is OK.
The G07 is a great chassis and definitely worth to fix !

Here's a good start for checking what's wrong:

http://www.rotheblog.com/images/arcade/misc/flowcharts/g07_flowchart.pdf

[Superully]

thx andré! that flowchart is nice! guess i'm going to start with the fuses then ...   

p.s. berzerk? 

[Superully]

oh, i forgot to mention: i don't have ANY NECKGLOW on the monitor!

[Superully]

ok, here's an update. i've been using that nice flowchart with the following results:

- checked fuse F901 for continuity 

- checked fuse F902 for continuity 

- measured voltage at resistor R1 (should be +120volts), result: +118.2V 

- turned up the screen control, no picture 

- check for CRT heater glow (is that what we call "neckglow"?), nothing there 

suggestion from the flowchart: open CRT heater circuit. check for broken wire, cracked pcb, bad solder joints on HV unit

here's the flowchart to illustrate what i've just written:



i guess i'm lost from here on out! what does it mean "open CRT heater circuit"? is that the pcb on the back from the monitor's neck? as always, i need some input! 

[level42]

The CRT needs a source for the electrons to shoot at the screen. The CRT heater generates those electrons. This is done by heating an element (much like a regular light bulb) in the CRT neck. The flow chart corresponds with your mentioning that there is no neck-glow.

The CRT heater voltage is usually 6.3 VAC and is usually "tapped" from one of the flyback windings.

First thing we need to know if there is this heater voltage on the neck pcb. IF there is.......we have a problem. In that case it's most likely that the CRT heater has died and it's end of the road for that CRT. (Chassis is still fine though).

I think I know where to measure it on the neck PCB but I want to be 100% sure, gotta dig up my defective spare G07 chassis to have a look...more later !

[Edit] First try to measure if the 6.3 VAC is coming from the flyback. Easiest way to test this is measure across C522 (acc. to the schematic). Remember to put your meter in AC voltage measurement.

[Superully]

[Edit] First try to measure if the 6.3 VAC is coming from the flyback. Easiest way to test this is measure across C522 (acc. to the schematic). Remember to put your meter in AC voltage measurement.

thx for your help, andré, i really appreciate it. it's frustrating that two of my best games, berzerk and wizard of wor, aren't working right now, but hopefully we'll get there eventually.

[noob mode on]

now on to the problem: i can't find C522 on the schematics. any chance of a picture? and what do you mean by "measure across C522"? how do i do that?

[noob mode off]

[level42]

In German: messen "über" C522. So put one lead on the left pin and the other on the right pin of the capacitor.

Do your best on the search, it's very near the Flyback (T502).

Alternatively, measure across pins H5 and H6 on the neckboard (much easier to reach)and we will work from there....be sure to measure the correct pins (use the schematics ) Look that you watch at the 19" version of the picture ! There should be a black wire and a white wire running very close to those pins.

[Superully]

ok, found C522, but it's impossible to reach without removing the entire chassis. that's why i've removed the protective sheet of cardboard behind the neckboard and it looks like the pcb has already been tempered with. i can't find pins H5 and H6, but there are pins labelled H9 and H10 which are in the same position as H5 and H6 are supposed to be. should i measure those?

here's a picture of my neckboard 

[level42]

Hah, that neckboard clearly has been broken. You can see the break running across the board from top-left to mid-right. It doesn't look like a full break, but it definitely cracked on that line. You can also see the break line by following all those solderings.

They repaired it with the big blubs of solder.

Good chance that one of those has a problem.

Indeed try to measure the H pins (weird that the numbering is different, I guess a different tube model). H stands for Heater.
So one lead on H9, the other on H10 (right at the end of the tracks where the pins are.

If you don't see 6,3VAC, I'm pretty sure there's a break in the track/solder.

If you don't see 6,3VAC, turn off the monitor and wait a couple of seconds.

Then put your DVM in continuity check (Diode/beep check) and put one lead on the H9 pin and the other on the closest soldering on the same track.
Repeat for H10. If one of the tracks is broken, you won't hear a beep.
Maybe you will have to wiggle the board GENTLY to get the break (or actually make the contact)....

If they tried to repair this with ONLY solder, it's very likely that it has failed. A repair like that needs a piece of bare solid core wire across the cracks. You will need to bridge the crack with it and make the copper trace bare around those spots. Alternatively, simply solder a wire bridge from one soldering island to the other, but make sure the wire is solid core (not stranded) and that it's a relatively thick wire.

Here's another way to repair it, although I have my doubts about the conductivity of the paperclip. I'd prefer to use a solid copper core piece of wire: http://www.therealbobroberts.net/bnb.html

While at it, check all of the cracks /resolderings, or even better, re-work all of them this way.

The thing is that if you try to repair this with just a solder blob, is that it will not be very solid, IF it already manages to cross the crack.
When things are going to be moved, it will get worse.

The solder will bond to the blank copper, but of course not to the crack where the PCB material is. So the solder is the bridge, where in my solution, the wire is the bridge, and the solder just keeps it in place.

I hope this all makes sense. Anyway, forget about C522....your problem is 99% sure in the neckboard

[Etienne MacGyver]

a paperclip can be difficult to solder, maybe you got a little piece around of this :


that will do the trick 

[level42]

That might work maybe a little bit TOO thick, but it could be OK. Make sure the wire is not wider or as wide as the track to bridge or else the solder won't neatly bond.

Read Bob Roberts text again Etienne, he says: "The Scotch-Brite pad is to remove the coating on the paper clip to allow the solder to adhere to it. "

Still, I don't really trust the resistance of the paper clip iron. Can't be as good as copper.

[Superully]

thx a lot for that lengthy explanation, andré! i don't have time anymore to do the measurements today, but i will surely tackle the problem tomorrow after school. i didn't remove the monitor during the restoration of the cab (because i didn't have a tool to discharge the monitor back then  ), so i'm pretty sure with all that moving / budging going on during resto soemthing must have happened to the neckboard. let's hope it's just that and it can be fixed. not sure if i can do that myself, but let's see. i'll report back to you guys tomorrow!

[Etienne MacGyver]

That might work maybe a little bit TOO thick, but it could be OK. Make sure the wire is not wider or as wide as the track to bridge or else the solder won't neatly bond.

then i would suggest the black variant of this , that is thinner  

Read Bob Roberts text again Etienne, he says: "The Scotch-Brite pad is to remove the coating on the paper clip to allow the solder to adhere to it. "

   my bad, i did not read that link..   it makes totall sence  

Still, I don't really trust the resistance of the paper clip iron. Can't be as good as copper.

i agree with you on this one