WG 25" K7000

[b3dr0ck]

I'm working on a monitor:
WG 25" K7000

I just put it together and plugged it up.  Turned it on, and nothing.  It appears the tube is getting no power.  I've got 128VAC at the plug, and then I tested the voltage at the back side of the fuse.  I've got 128VAC on the back side of the fuse.

So - what should I look at next?  The Flyback, HOT?  Suggestions?

I posted this a year ago.  I'm a relative newb here.  I've gotten everything out and I'm building a new cab.  (My second one every)  I have plenty of parts - I had 4-WG 25" with K7000s.  I've never seen this monitor work.  The last suggestion I got was to test the high voltage.  All I have is a normal volt meter.  I did try to test the resistance of the HOT.  I do not think it is shorted.

The chassis has not been cap'd.  That's still a little above me, and I have a tested K7000 chassis that works.  I figure connecting it to this monitor would be easier than cap'ing everything.

[buffett]

measure D19-23 to see if they have shorted.
test your H.O.T. Q11 to see if its shorted.
test C36/38 to see if there shorted.
test your VR, IC4 to see if its shorted.

if any of those parts show bad in circuit. pull them and test again.

post what you have done and i can try and help you get it fixed.

i repair them if you don't want to do it.
pm me.

Peace
Buffett

[b3dr0ck]

ignorant question, but I know no other way to learn

How do you test for a short - I'm thinking set my Volt meter to resistance and put red probe on one leg and black probe on the other leg - if they show 0000 then there is no resistance, and it's shorted.  Is that how I should do it?  Or ... do I ground the black, and test each leg separately with the red proble, again looking for 0000 resistance?

The HOT has 3 legs, do I just test leg independently

[lilshawn]

I just put it together and plugged it up.  Turned it on, and nothing.

you didn't by chance happen to just PLUG it in did you...this monitor requires it to be plugged into an isolation transformer. if it is plugged directly to the mains the voltage regulator blows up.

ignorant question, but I know no other way to learn

How do you test for a short - I'm thinking set my Volt meter to resistance and put red probe on one leg and black probe on the other leg - if they show 0000 then there is no resistance, and it's shorted.  Is that how I should do it?  Or ... do I ground the black, and test each leg separately with the red proble, again looking for 0000 resistance?

The HOT has 3 legs, do I just test leg independently

depending on who made the meter depends on what the 000 means.

my meter for instance when the probes are not touching it reads O.L (over limit (basically open circuit or the resistance is so high it's higher than the meter can read)) if i touch the probes together it reads 0.000 (short)

another i have reads 0000 for open and then 0.000 for short. so basically i have to mind the dot with that one.

what you want to do is put your black probe on the middle leg and then touch either of the 2 outside ones. if either leg reads short(0 ohms) or low resistance (1,2,3,4 ohms etc.) it's bad. it should read really high (1000's of ohms) or open... reverse red and black and test again for good measure. it's not a 100% test but will give you an idea if it's toast or not.

[b3dr0ck]

No, I plugged it up to a fully tested iso. transformer from another working cab. with a working WG 25" K7000.

I got out my multi-meter and turned it to 200K Ω
I touched probes together, it settles down to 000.0

HOT - Q11
I touched black probe to middle leg, red to right = climbs up 12.0
I touched black probe to middle leg, red to left = climbs up 12.0

D19 - number climbs
D20 - number quickly settles to 000.0
D21 - number quickly settles to 000.0
D22 - number climbs
D23 - number quickly settles to 000.0

C36/38 are big ones, hard to get to, multiple legs, not sure what to do - didn't test
IC4 same as above
VR - I don't know what that is

[lilshawn]

D19 - number climbs
D20 - number quickly settles to 000.0
D21 - number quickly settles to 000.0
D22 - number climbs
D23 - number quickly settles to 000.0

the reason it's climbing up is because with a resistance test the meter generates a voltage and reads what comes out the other side. this voltage is being pumped into the rest of the circuit (charging capacitors etc) capacitors are a low resistance item until they get charged up, as they charge the resistance goes up and up untill they no longer conduct. by testing in circuit the voltage is being sucked up by the capacitors giving you weird climbing readings as they charge up.

one side of these diodes needs to be removed from the board for proper testing. doesn't matter which. you must also use the diode test function on the meter. the black probe will go to the stripe side of the diode. they should read 0.5 or so depending on the particular diode. if they read 0 they are shorted and need to be replaced. if they read nothing (meter doesn't respond when connected) they are open and need to be replaced.

[b3dr0ck]

<discouraged>

So ... it does not appear I can really test much of the monitor without effectively taking it apart.  If I have to start cutting wires and desoldering stuff, I should probably start working on putting together the working monitor and chassis I have.

Let me ask this - is there a way I can isolate the high voltage?  I just want to see if the problem is with the  chassis, or the neckboard/tube.

See attached
How would I "see if CRT filiment is lit"?  Visually in the neck tube?

[lilshawn]

So ... it does not appear I can really test much of the monitor without effectively taking it apart.  If I have to start cutting wires and desoldering stuff, I should probably start working on putting together the working monitor and chassis I have.

fixing blown monitors can be fairly involved if you don't know the proper way to diagnose it. what you really need to do is isolate the problem and go through the systems that control that function and find out why it's not doing it's job. really, finding out what's still working.

Let me ask this - is there a way I can isolate the high voltage?  I just want to see if the problem is with the  chassis, or the neckboard/tube.

you can, but you will need to build yourself a test piece with a household 60 or 75 watt light bulb and socket with wires on it. you will need to disconnect the high voltage from the rest of the system (lifting a jumper) but you need to maintain a load or the power supply won't work...this is where the lightbulb comes in. but let's make sure we are getting high voltage in the first place...you aren't blowing the fuse so your already several steps in the right direction already.

the VR (voltage regulator) is an integrated circuit that supplies your high voltage. it has an input and an output. you need to see if the output is 130 volts DC. just check it on the big huge white resistor on the side. if it's really high (160's) something is open if it's low something is shorted and loading it down.

How would I "see if CRT filiment is lit"?  Visually in the neck tube?

yup. it would glow a little orange inside the clear portion of the neck of the tube. that is the heater for the guns.

not to discourage you or anything, but should you feel that you don't want to tackle this project a Wei-ya model 1220-H replacement chassis will work with this tube.

[b3dr0ck]

I reconnected power to the monitor
1 - there is nothing visable at the yoke / neck tube
2 - double checked the voltage on the back side of the fuse, 128 vac
3 - still not exactly sure what the VR is, but there is a 3inch rectangular white piece that is mounted outside the shielding horizontially, on the side of the HOT, with power on, I touched the red probe to either side of the IC with the black probe grounded - I got nothing, 0. 

With it off, I looked back over D19-23, the results I gave before look right.  I checked D24 as well, it looks like 000.0

[lilshawn]

looks like the voltage regulator (VR) may have gone on you. Should be an SCR type number it's a black thing mounted to the aluminum heatsink somewhere around where the big white block is.

if you can clamp the meter positive to the white resistor and ground the black lead... power up the monitor...does it show a brief flash of power (like a quarter or a half second) right as the power is supplied or does it stay dead?? (the power flash may be too short for the meter to pick up, the meter may go blank as it goes to read the voltage but it's gone before it gets the chance.)

[b3dr0ck]

OK Just to clear some stuff up

The 2 pictures attached -
1 - is the VR?
2 - the black thing you mentioned on the other side of the shielding, I think that VR4 - what's that, does that need to be tested?

(I'm going to test the voltage now on the VR - I'm setting it to DC, right?)

[b3dr0ck]

Well ...

I hooked power up to my good WG25" K7000 (I wanted some control), turned it on and checked the DC at the VR
at the red end (which I'm thinking is the input)     164.3
at the blue end (which I'm thinking is the output)  126.2

I connected power to my dead monitor we've been working on, and to my surprise I did see a flash of power on the VR at the input - red end.  I did it like 3-4 times.  I would flash up to 1.5 VDC, mostly around .6.  Nothing on the blue end

So ... I feel good that we may have diagnosed something, I do not know what ATM.

[lilshawn]

the white thing is a load resistor, it applies a small resistance (a few ohms) to the output of the VR to help keep the voltage steady.

the black thing is the VR (voltage regulator) it supplies the 130 volts DC for the high voltage circuit.



the circuit goes:

ac input goes into a rectifier that changes the 120v AC to a rough 120v DC...

the rough DC gets smoothed with a few capacitors and sent to the regulator. where it gets changed to a nice regulated 130 volts DC.

this voltage gets stepped up by the high voltage transformer to a couple thousand volts and used.

if the voltage gets too high (often because something has gone open circuit) the VR gets shut off by an xray circuit.



there is a bunch of other things that happen too, but basically this is the meat and potatoes.

you need to make sure there is something coming out of the VR to see if it's working. you can test it's output of 130 volts DC either at the VR (hard to get the little pin) or the white load resistor (easy because it's right there).

[lilshawn]

I connected power to my dead monitor we've been working on, and to my surprise I did see a flash of power on the VR at the input - red end.  I did it like 3-4 times.  I would flash up to 1.5 VDC, mostly around .6.  Nothing on the blue end

So ... I feel good that we may have diagnosed something, I do not know what ATM.

hmm...hard to tell, you might have an issue with the rectifier... you'll have to pull up one side of the diodes and check them. d19,20,21,22 (I believe... i don't have one in front of me to be sure.) in the rectified voltage going into the VR is dirty or noisy due to a shorted diode it won't operate properly.

[b3dr0ck]

The Troubleshooting chart (posted above) says

No High Voltage - Check B+ (123V) at IC4. PIN4:  Neck Board P202. Pin3
(I now know the IC4 is the VR, from my pic)

I'm guessing it's going to be "No B+"

Says - Check AC INPUT
   Fuse good
   HOT good
   Check for shorted B+ Regulator, IC4

What's the B+ Regulator?

[lilshawn]

The Troubleshooting chart (posted above) says

No High Voltage - Check B+ (123V) at IC4. PIN4:  Neck Board P202. Pin3
(I now know the IC4 is the VR, from my pic)

I'm guessing it's going to be "No B+"

Says - Check AC INPUT
   Fuse good
   HOT good
   Check for shorted B+ Regulator, IC4

What's the B+ Regulator?

IC4 is the regulator.

we arent sure if the issue is the regulator or the input from the AC mains. wee need to check the diodes that rectify the AC to DC voltage to be sure they are good. if even one is shorted, it causes all sorts of things to happen.

[b3dr0ck]

Well it's come down to this - using a soldering iron.  I knew this moment would come.  I've been putting it off for a year now.

I guess I should start looking toward replacing the flyback and HOT on the other K7000 I have, and probably thinking about a Cap kit.

I'll do it - may take me sometime.

[b3dr0ck]

Well well - I took off the K7000, and decided to hook the other K7000 that I knew the HV was working.

I plugged up the 2 prong - grounding/deguasse (not sure what it does) wire
I plugged up the 4 prong color wire to the board
I connect the ground wire to the grounding/deguasse thing
Plugged the neck board in
Connected power

(connected the video input the second time)

Took a moment a call for assistance if it all blew up

Turned it on, and it worked ... somewhat, at least nothing blew and we had HV, but everything is green - what does that mean?

[lilshawn]

trasistor shorted?

check Q202 ? i belive... even just swap it with one of the other 2 if the color changes to red or blue screen you have a shorted transistor.

[b3dr0ck]

OK - took the neck board off, and looked and one of the pins were bent.  I straightened it out, plugged it back in, and now the screen is a pinkish yellow color with a band of red on the right hand side.   

The yoke pins and deal do not look good.  (this is a real suck question)  Can the tip of the yoke that plugs into the neck board be replaced?

I'll attach a pic, when I get inside.

(I've got duplicate threads on this - sorry)

[b3dr0ck]

See other thread for pics
http://forum.arcadecontrols.com/index.php?topic=119354.0

(There is still hope, there is another!  I have one more CRT.  It is my last of the monitors to get this NEO GEO MVS1 built)

[b3dr0ck]

i'm connecting the monitor to the cab I'm rebuilding

got a question about the isolation xformer,

1 - I use the 2 connectors at the top, right?
2 - It doesn't matter which cord I connect to the top terminal, black or white?
3 - what about the bottom, it's orginally connected like this (see pic) is that right?  It connection coming from the filter.
4 - voltage at that top terminal should read - 125V  - that's DC right?

[ed12]

top is the output of the x-former
bottom is the input
the e=grnd=green wire
the 0=white
the :tap: is to set the :ac-voltage:-->input ie 110-115-120
the top is set to 1 amp >fuse it<

i'm connecting the monitor to the cab I'm rebuilding

got a question about the isolation xformer,

1 - I use the 2 connectors at the top, right?
2 - It doesn't matter which cord I connect to the top terminal, black or white?
3 - what about the bottom, it's orginally connected like this (see pic) is that right?  It connection coming from the filter.
4 - voltage at that top terminal should read - 125V  - that's DC right?

it's all ac voltage period,use the line filter,blue=white brown=black

ed

[b3dr0ck]

OK

How does this look?

The cab. switch even works

The top the the x-former reads 122VAC - which is good ... right?

I still need to hook up the Switcher - I guess I'm gonna need to get an AC dist. block to get power to it.

[ed12]

hi
thats about right
i hope the 4 wire's i c are going to a switch ?
if so then where u hooked to the :input: to the xformer,is where u will hook your power-supply,rem 1 thing switch mode power supply's :smp's: are already isolated from :line:...the x-former to is isolate the monitior
in case it is not :smp: style,we tend to call it a saftey thing,another thing here..is that x-former WILL NOT HANDEL the full load of a game
ie power supply and monitor
but from what i can c nice work so far

ed