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A while ago, when switching on my cabinet no picture was being displayed. Today i'm checking out the game and notice that the monitor has no neckglow and is "ticking". A very distinct ticking that is at approximately 50 Hertz or so. I guess my monitor just died and that the problem is in the power supply. Or is it the flyback that passed away??
Does anyone have some experience in this area?

It's a neo-geo cabinet with a (yes, i know) 60 in 1 jamma board and an intervideo (??) 25" monitor.

I am going to guess your monitor is a K7000. Would be nice to verify that with a photo or something.

But going on that assumption your HOT probably is dead. The clicking sound you are hearing is the B+ supply dealing with a short circuit somewhere on the PCB.

I will post a pic. Thanks for your quick reply.

I completely missed your comment on the intervideo monitor. but what i said still holds true for the intervideo. The hot is probably dead. To check, remove Q3 which is a BU503 and do a diode test across it. pretty much measure every pin to every other pin. if there is a 0V (short) on any of those pins then thats your problem. If the hot is fine then you will have to do a LOT more digging.

It's this one:

http://www.andysarcade.de/data/coinop/videogames/raster%20monitors/intervideo/intervideo_vp_series.pdf

Mine is version 6, manual is for version 4. (22.0329.4).

I will check Q3.

Okay,  desoldered it, it reads each 2 times: 0.012 0.026 and 0.035 volts. (Measured it 6 possible ways)
That thing is dead. Will order a new one this week.

Thanks for the help so far. I will update once i've got more info.

oh yeah, thats dead.

Replaced Q3, measured it before putting it in, and got .5 or so 2 ways. So that one is good (or was good for that matter). Still the same issue unfortunately. I still hear it ticking distinct, at about 50Hz or so.
Next step: i will check out all the transistors in that area.
Is it possible this is caused by a defective flyback???

I will also recap this thing.

I noticed the image was a little unstable from time to time. It glitched out of sync for a few frames and the image was sometimes briefly shaking.

it is possible the flyback is causing this but i am not sure, i haven't personally seen a flyback cause a main power supply short before.

The one annoying thing about these types of monitors is the power supply will click if there is an overload or there is no load. So its possible that almost everything is fine and there just isnt a load on the supply.

I would go ahead and cap it. If there is a bad cap somewhere it can cause a no load failure.

A flowchart is available, will check that baby out.

I followed the flowchart on page 8.  Measuring the voltage on cathode of D12, must be >= 149Volt. Is around 3.5Volt.
Disconnected the yoke, now it measured 189 Volts. So, according to flowchart Q3 and D16 can be defective. Allready swapped Q3, so D16 can be an issue too i guess.

Okay, desoldered D16, it measured 0.5V, the correct way. So i guess that one is good. Hmmmpf, what now???

Do a cap kit. As i said before, you don't know if it is failing from a short or from an underload. Its entirely possible you just have a bad cap.

Okay, will do. Thanks again.

Recapped the shit out of this thing, still no improvement. Can a diode be defective even though measuring it gives a normal value??

diode that measures properly should be fine. I am not sure how to tell someone to fix this type of monitor at this point. Maybe start probing across each capacitor your repalced with your meter on continuity mode. Try to see if there is any short on any of those caps. I am not saying the caps are bad but generally when something is shorted you can see it at a capacitor.

I followed the flowchart and found a defective diode D13 (from the +24V circuit) also died. It's a BY299. I replaced it with a BY255 which I got on stock but this didn't even fix the issue.

I didn't mention this however: when the monitor is "cold" (I guess all the caps are discharged) the monitor tries to power up when switching on the power. I hear the screen getting static for just a second and then the power supply goes "down".

I will order a full set of replacement diodes and transistors. Maybe that will help.

O, before I forget. The flowchart states that there should be around 7/8 Volts on pins 15 and 16 of IC1 (TEA2164). Mine reads about 6 Volts.

Was reading the flowchart to add the IC name for the previous post and noticed this in the manual:

(http://local.hadecom.nl/pics/arcade/outrun/ORR014.jpg)

The voltage on the yoke is about 180 Volts. Probably there lies the issue. Will check that this evening after work. I'll keep you posted.

If i am following correctly it sounds like your monitor is going into high voltage shutdown. The first switching mode power supply should be generating 140V. if there isn't enough load on the system that could cause it to ride high but something is certainly going on with that. The yoke should have B+ across it.

What's B+ ?

B+ is what the industry calls the main power supply rail. This is what feeds the horizontal output transistor. according to what you just posted the B+ should be 146-149V. If it is going to 180V then either it is unloaded or somehow the primary supply reference got messed up. Generally it is not a good idea to mess around with the voltage feedback of the primary supply so it is likely something else is going on.


Usually when i am stuck like this I will try to isolate the power supply anyway I can.
So often what I do is remove the HOT, find the B+ at a good spot. usually a test point or the filter cap for the B+. then solder a 10-20W load onto it. Like a lightbulb or something else. If the supply starts working when the load is there then you will know the supply is fine and you need to find out why the HOT isn't running.

Thanks for the tip.

Did some measuring yesterday. Yoke on: 149Volt is now about 3Volts. Yoke off: 163Volts.

When measuring behind diode D2 in both situations: 6Volts. And that's strange, this should be 320VDC. Maybe a floating ground???

Also replaced the NTC, this was 27 ohms and dropped to 17 ohms after heating it up with my soldering iron. Will check it out this evening. (Again)...

I am going to make some assumptions with that information provided.

Your input power supply is fine, I think it is going into underload foldback. This is very different than a short and is caused by having too little load, this means most likely the HOT is not doing its job.

I'm not sure the reason for replacing the NTC but by its own name the resistance should drop when it is heated. (Negative Temperature Coefficient)

I am not sure if D2 is the same as as the schematic but D2 is listed as being one of the input bridge rectifier diodes. On the annode side it should be 120VAC. The cathode side should be 170VDC but that should be with respect to neutral, ground only if the monitor is properly grounded. IF the monitor is not grounded you have no reference to measure with respect to the frame. Also worth noting, if you are trying to measure D2 with respect to the "ground" that is marked on the PCB that won't work since that ground is electrically isolated from mains input.

I need to try to think how to tell you to test certain things on the monitor. What multimeter do you have so I know what features it has.

I forgot to mention the NTC, this indeed will decrease in value once warmed up. The value should be around 7 Ohms (according to the manual) but was 27. So i replaced it with one i use in my pinball machines to avoid the circuitbreaker issue.

FYI: i know my electronics, analog and digital, but i'm lacking the experience to troubleshoot this issue. If i'm measuring a value I use a decent multimeter and a scope, unfortunately no fluke but these kind of issues makes me second guess why i don't own a fluke multimeter.

D2 is the same as the D2 on the schematic. Over here we have 240Volts AC. I will do a measurement tonight, got so little time unfortunately.

Thanks for your patience!

Well hell if you have a scope that makes it a ton easier, I am so use to people not owning them that I am always trying to figure out ways to measure stuff with the wrong tool.


I wouldn't be too concerned with the NTC. It is just acting as a current limit to charge up those filter caps. If the value isn't quite low enough it will heat up and keep going lower (until it pops!)

I have to say the power supply is one goofy flyback circuit. Can't say I have ever seen anything like this before.

Anyways, i think the power supply is just fine so lets move on. You can probe fairly freely on the board since it has an isolated power supply.

use your scope and probe the base of Q2 and the base of Q3. Ideally you would see 15.7khz at both.

The driving chip is a TDA2593 https://www.tu-chemnitz.de/etit/zentral/ddr/ds/TDA2593.pdf
Check to see if you are getting the 14uS pulse into Q2 and go from there.

The grounds are seperated too. Now i know why i don't get a 320Volts reading. Will dust off the scope.

Couldn't it be the case that the monitor is in "power save" if it doesn't receive any input? I get output on the vga interface if set to vga modus, but i can't test the rgb output else than with a scope. Will do this of course, but can it be that the monitor is functioning correctly and we are thinking just wrong??
Doesn't explain the broken Q3 however, that thing was broken as hell.

Anywayz, will check the 320 Volts DC and will work my way down. I agree with your idea that the power supply shall be okay, just want to rule that one out.

The monitor shouldn't have a power save feature, just going from the circuit it has a PLL to keep the HV flyback running without an input that is also feed into the input flyback for sync.

To test the power supply you are going to want to wire in a 10-20W (120V) lightbulb. i have used CFL's in the past to do this, just get one that has a real power rating of around 10-20W which is equivalent to about 60W incandescent.

Wire the lightbulb across C12 to load it down. I usually remove the HOT as a starting point so you aren't powering up the HV flyback and hurting yourself.

Pretty easy test because if the lightbulb lights up, your power supply is working.  To test with the scope just look at the waveform and make sure you are getting fairly smooth 146-149V DC at the cap and then move your scope ground over to the AC mains ground, grab that at C79, and probe the base of Q1. that should be around 15khz with probably a low duty cycle.


i think it might be worth chatting live for this since it takes a lot of words to describe everything.

Will surely try that lightbulb load. This weekend was a little hectic and a tried the quick and dirty method where i replaced IC1 and IC2, and a couple of diodes. After i replaced the ic's the power supply tries to switch on when the yoke isn't connected. I'm really not sure if this behaviour was present before, I'm pretty sure the power supply even didn't want to startup when the yoke was disconnected, but not for 100%.

Thanks for your live chat offer, we need to schedule that because of the time difference. What do you use, skype? Need to fix a camera for that.
But first I will check that lightbulb thingie and poke around with the scope. Will post some screenshots.

Hi Ian,

Nice to see your appearance on John's channel a couple of weeks ago! Now I know who i'm talking to.

Just connected the scope to the base of Q1 (anode of D7). I connected the ground of the probe to C7 to ground the scope and bam! all lights went out in my house. I'm stuck and real close to giving up. I really don't understand this schematic.

Got any ideas?

Decided to swap the flyback. Got it out and found a burned stain on it so maybe that's where the problem is. Now there is a black cable going to the socket that connects to the neck. How can i get that black wire out of that socket???

Pics:

How must i remove the black cable from the neck socket? Must i desolder the socket from the neckboard first?

(http://local.hadecom.nl/pics/arcade/Flyback1.jpg)

(http://local.hadecom.nl/pics/arcade/Flyback2.jpg)

Dark spot on the flyback. Can this be the issue??

(http://local.hadecom.nl/pics/arcade/Flyback3.jpg)

Got it replaced. No luck unfortunately. I'm stuck. Damn!

anyway you could isolate horizontal and vertical yokes?

If the yoke is shorted that could be pretty bad.  I am really just not sure how to help. Sounds like it has something to do with the yoke or driving circuits with the yoke.

Thanks for your input Ian. Fortunately i found someone who can fix the chassis or has a replacement for me.

I will check some standard crapp before shipping the chassis.

One question though. In one of John's episodes John mentioned the use of an isolation transformer is mandatory. What do you think regarding this issue. Can this be the cause why my monitor is defective?

I'm a donk, a stupid donk. I mounted the HOT directly to the heatsink. The old one was mounted without isolation as well but i guess in the years the package has changed or didn't i notice the mica on the old transistor maybe?

So i mounted a new hot, isolated it, and.... succes!

Thank you Ian for your support and patience. Case closed.