Final Fight K7000 Monitor Problem

[mecha]

You're talking about the one thats wrapped around the tube (looks like for static discharge) right? I did connect that when I was having the fuse blowing problem.

Should the green ground wire in the pics be connected to the monitor chassis?

run what's called the "earth ground" (this is the green wire that comes off the ground plug going to your wall outlet) to the metal tray -- this should connect via a metal lug in the bottom of your cab, most likely linked to the isolation transformer.
I *think* if I'm understanding this correctly that the ground screw for the monitor works how the mounting screws for the chassis tap into the grounding traces around the perimeter of the deflection board connected to the mounting tray, which then connects to the earth ground off the wall outlet... what a mouthful!

hope that makes sense. you want the green ground wire off the wall outlet, not the "synthetic" ground coming from the black wires in the power supply.

and if anyone out there wants to call me an idiot and say I don't know what I'm talking about, please correct me.

 

[syplex]

Replaced the HOT with the new HOT that came in the mail, checked everything and hooked it all back together in the cab.

Powered it up and no fuses blew! The tube was powered, neck glow, but no game picture. Turned up the brightness then the tube picture was white, started turning it down and then the tube shut down, where the display went white in the middle... no neck glow.. so I quickly turned off the cab and I could smell a burning smell. I had it on for no more than 90 seconds. I couldn't immediately see anything that looked blown or fried but I wont know until I pull everything out and start testing again.

What could it be? Everything that I tested before installing the HOT tested fine. What should I check next?

 

[mecha]

solid white picture? did you have the game plugged in too, or no video signal?

I don't know of any instance in Final Fight where the screen was even white, so I'm going to take a wild guess and say you had the Screen on the flyback turned way up and you also turned the Brightness knob up (not sure if your controls are hardwired to the deflection board or if yours has a remote) and you might've triggered the HV shutdown.

I don't know jack about adjusting or even measuring the B+, but I say turn the Screen brightness down on the flyback, and dial down your Brightness and Contrast controls as well. see if your monitor stays on at least like that, and if that burning smell gets worse or something.. I don't know what that could be, but you probably overdrove something and it went into shutdown.

maybe wait until someone who knows what they're doing with these can give you more feedback instead of my ramblings.

 

[syplex]

Well I checked it out a little more, the main cabinet fuse blew. I had the flyback screen turned up about halfway (I may have had it lower and turned it up while it was on cause when I first powered it up the dislay was completely black). I just turned it all the way down and put in a new fuse and it blew instantly. I will take out the board tonight and re-test the HOT and VR and all the other components I had already tested. Should I just replace the common problem pieces even if they test ok? Looking for some more ideas!

Edit to add: It was pretty much solid white-ish that reacted to the brightness dial. I had the game board connected. I'm going to have to go thru the K7000 service manual and do some more testing. The thing is how do I measure B+ when it immediately blows a fuse and I'd like to fix the problem without continuously replacing the same parts (I currently only have one extra HOT and two VRs).

 

[syplex]

Ok I took the board back out and upon inspection discovered R101 was loose. Removed it and the pads are completely burnt off the board. It measures 6.23K when it should be 6.8K which is a bit out of the 5% tolerance (about 8.4% off) but obviously its bad so I'm going to replace it.

I also noticed R105 (thermister) has cracked plastic. Not sure the specs on it since the service manual just says thermister.

The good news is the HOT didn't die, but the VR looked like it did cause there was a low amount of impedance between pins 1 and 4, but when I removed it it measures OC. So, something else must be shorted cause that normally measures OC in-circuit right?

*Edit: Pads weren't burned off on R101, after taking a fiberglass pen to it I see the pads are intact. One of the solder joints broke free though possibly due to excess current because of the lower than spec impedance.

*Edit to add: Started testing components on the neck board and everything was good except C205 measured 1697 pF but it should be 1500 pF. What kind of problems would this cause, if any?

 

[mecha]

higher capacitance would probably feed too much juice to a certain component. when it comes to caps, it's to my understanding that when you replace them you can go with a higher voltage, but the capacitance has to be the same.

didn't you say you re-capped this? there's many instances I've read on here where people installed new kits and had bad caps in them. lol

just one of those things that happens.

glad to see you're making some headway on this.

 

[syplex]

Yeah re-capped it but C205 is a ceramic cap and wasn't included in the cap kit.

 

[syplex]

I replaced C37, C38, and R101 and fired it up, checked B+ and it was 160V. I discovered R20 R18 was shorted to ground via a lead soldered across the bottom of the board. Does this sound like a fix for something? I removed it and re-soldered lots of joints and B+ was still 160V. I removed D10 and the CRT doesn't come on (no neck glow).

I have burnt out two hots and several cabinet fuses so far. My next step is to replace D18 and C36 (which both tested ok) since there are only so many components that could cause this problem.

I also ordered a new T2 transformer because mine is reading shorted out on the secondary winding side. Anyone know what the primary and secondary impedance is supposed to measure?

 

[Peale]

This sounds a lot like the issues I'm dealing with on at two different K7000s.

As for that lead, sounds like a factory mod by WG. Put it back.

 

[syplex]

The shorted out resistor was resistor R18 not R20. Take a look at the picture, shorting R18 grounds Q4's base which is part of the forced blanking circuit. The manual says most video signals don't need the forced blanking but the circuit is there to support video signals that require it.

Perhaps FF doesn't require forced blanking and this is why its shorted? Can anyone confirm that their K7000 (mine's a k7901) has this mod in place?

Also anyone know the impedance for T2's secondary?

 

[orion3311]

I have one at home I can see if I can measure for ya.

 

[syplex]

Thanks orion!

 

[orion3311]

Sorry totally forgot about this...will make a note to look tonight unless someone can help you sooner.

 

[syplex]

np orion.

If someone knows the impedance of a working K7000 T2 transformer or can measure it (in or out of circuit) please do so. Because when my parts come in this week I will have replaced the following:

D18, Q11, IC4, C36, C37, C38, R101

And all the caps in the cap kit: C10, C11, C12, C13, C18, C20, C21, C22, C23, C40, C42, C45, C46, C48, C50, C56, C57.

I have also ordered a new T2 in case mine is bad.

I ran it up without the thermistor (R105) connected which should disable the degaussing coil in case it was shorted. I will try running it with the coil disconnected (P3) as well.

Would B+ of +160V kill the flyback? I put in a new flyback when I installed the cap kit but now I question whether it is fried.. no cracks in it that I can see though.

I am going thru the service manual and randy fromm flowcharts and one thing to check is the filament circuit. Do I test this by verifying R213? Should the filament fire up with B+ of +160V? I checked R213 already (my dmm only goes down to tenths of an ohm) and it measures good @ 0.6 ohm.

*Edit to add*

I also ordered a new IC2 in case it got jacked up. How do you test if IC2 is bad?

Also, how do I test for the yoke shorted or grounding? Unplug P4 and test impedance between red and blue and then between yellow and green?

 

[KevinMullins]

B+ being 160V+ is going to put it in shutdown, and the cause of the high B+ may be part of what's blowing fuses.

You need to check the VR for shorts between pin 1 & 4.
What is the voltage going into pin 1 ?
(pin 1 is the input, pin 4 is the output, output is where your B+ is derived from)

And just to humor me, can you unplug and check the continuity of the ISO transform between the primary and secondary windings. (top to bottom) Just want to be able to say we've checked it.

 

[syplex]

You need to check the VR for shorts between pin 1 & 4.
What is the voltage going into pin 1 ?
(pin 1 is the input, pin 4 is the output, output is where your B+ is derived from)

I have checked that, not shorted, and I have replaced it with no change.

I will check the voltage going into pin 1 and get back to you.

And just to humor me, can you unplug and check the continuity of the ISO transform between the primary and secondary windings. (top to bottom) Just want to be able to say we've checked it.

The ISO voltage appears good on the secondary but I have not checked continuity on the ISO, I will do this as well.

 

[syplex]

And just to humor me, can you unplug and check the continuity of the ISO transform between the primary and secondary windings. (top to bottom) Just want to be able to say we've checked it.

Checked it, no continuity. Parts are coming in today so in the next day or two I will be replacing D18 and possibly IC2.

How do I test IC2? Its not shorted Vcc to gnd and I can see a diode drop but I have no way of testing if it actually works.

 

[syplex]

Ok I replaced D18, C36 and C38. Still no go.

You need to check the VR for shorts between pin 1 & 4.
What is the voltage going into pin 1 ?
(pin 1 is the input, pin 4 is the output, output is where your B+ is derived from)

Voltage going into pin 1 of VR is about +165V, voltage on pin 4 is +160V.
Also, pin 2 of VR is about +143V.

Pin 1 looks good according to the service manual, but Pin 2 is supposed to be +125V. I guess I'll start looking at R84, R85, R102, R86, C56 and C55.

 

[KevinMullins]

Should have asked sooner, but which voltage regulator do you have in there ?
(STR30130, STR3130, etc)
I always forget there's a slight pinout difference between them.

 

[syplex]

VR is STR3123.