New Life Games LLC
Monitor Repair Log and Database. **Arcade and Gaming** => LCD and CRT Monitor Repair Tech Support => Topic started by: shortrackskater on October 17, 2016, 06:22:03 PM
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I have a 19" Kortek CRT monitor (In an older Game King) that just has a black screen. There IS power getting to the monitor.
(I was able to slide in an LCD to test all the signals)
And when I power up the slot and remove the CRT, there is no discharge on the picture tube. Where can I start on this?
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:Scratch-Head: so are you saying that the LCD showed the game screen?
i made up these shotgun kits years ago for the other techs so they could repair monitors too...we had about an 85-90% success rate with these kits. many CRT's that were pulled from the floor was due to "blackout" or "no power" problems. be aware that i upgraded the voltage on some caps but the microfarads stays the same. good luck!!
KT-1703 & KT-1903
C421: 10mf, 50V
C504: 220mf, 50V
C123: 470mf, 25V
C126: 470mf, 25V
C122: 1000mf, 35V
C119: 1000mf, 35V
C107: 47mf, 50V
C108: 1mf, 50V
KT-1948
C411: 10mf, 250V
C414: 100mf, 50V
C415: 100mf, 50V
C412: 10mf, 50V
C417: 10mf, 50V
Q403: IRFS540A
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Yes the LCD works. I just happen to have one for a while that i could test it with.
And the CRT has a black screen. I can see the power light on the touch screen controller.
I have a KT 1982S
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Yes the LCD works. I just happen to have one for a while that i could test it with.
And the CRT has a black screen. I can see the power light on the touch screen controller.
I have a KT 1982S
give me a few and i'll see what i can dig up on the 1982; i'm pretty sure i kicked them around too back in the day. since your LCD worked good you can definitely say the problem is with the CRT circuit boards. often changing capacitors will bring it back to life. other high failure items for a "blackout" CRT are HOT, FET, diodes near the HOT and FET and maybe the flyback transformer.
have you visually chaecked the board for puffy caps or burnt components?
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found your schematic! :applause: might be helpful, especially if you are going to order components... :yes:
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Thanks! I'm sorry I forgot to say I have a manual for it, but this schematic is better quality.
I'll take another close look at this CRT and see if there's anything notable.
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Kforeman.. I have a question for you since you have worked on them. I'm use to working on Ceronix Chassis, mostly 1492 & 1493 unit. With the Ceronix you didn't have to use a tool to discharge the high voltage lead to the CRT because they have self discharging capacitors. Do the Kortek chassis need to be discharged at the high voltage lead to the CRT? I have a few 17" GK machines here that could have some problems and I just want to be prepared..
Thanks, Gary
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Kforeman.. I have a question for you since you have worked on them. I'm use to working on Ceronix Chassis, mostly 1492 & 1493 unit. With the Ceronix you didn't have to use a tool to discharge the high voltage lead to the CRT because they have self discharging capacitors. Do the Kortek chassis need to be discharged at the high voltage lead to the CRT? I have a few 17" GK machines here that could have some problems and I just want to be prepared..
Thanks, Gary
hi Gary! honestly i always discharge the CRT when working on a monitor just to cover my ass...i'm no electronics expert, i simply wasn't scared to jump in back when we lost our "monitor tech" and so i ended up figuring out how to repair most of what i took apart.
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Okay thanks.. I'll have to find my home made discharge screw driver with the wire and clip to ground the chassis..
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Okay thanks.. I'll have to find my home made discharge screw driver with the wire and clip to ground the chassis..
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I have one of those too! They come in handy :lightningbolt:
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give me a few and i'll see what i can dig up on the 1982; i'm pretty sure i kicked them around too back in the day. since your LCD worked good you can definitely say the problem is with the CRT circuit boards. often changing capacitors will bring it back to life. other high failure items for a "blackout" CRT are HOT, FET, diodes near the HOT and FET and maybe the flyback transformer.
have you visually chaecked the board for puffy caps or burnt components?
Okay, finally, I took a good close look at everything I could, that's visible from flipping the CRT up, down, sideways, crossways, etc... didn't see anything notable, no puffy caps seen.
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do you have a multimeter? looking to test the HOT...diode/continuity test setting on meter, black lead on center leg of HOT, red lead on the outer legs one at a time, should read like a diode on the meter. if its a continuous beep the HOT is shorted. sometimes you have to take the HOT out of circuit to get true reading. i think the HOT is Q704 on your board
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I'll get to this. Got busy recapping a really old CRT. I'll get to this
tomorrow soon I hope. Thank you for the help. :applause:
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It's apart.
Looking for Q704 but not having luck. This is more difficult than my F1 monitor.
Is this a transistor or diode? Isn't Q a transistor?
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It's apart.
Looking for Q704 but not having luck. This is more difficult than my F1 monitor.
Is this a transistor or diode? Isn't Q a transistor?
sorry man i've been hella busy lately... yeah the HOT is a transistor - Horizontal Output Transistor thus the acronym HOT. it's usually the largest transistor on the board and is near the flyback transformer too. testing it with a meter is like you would a diode with the center leg of the HOT being the cathode side if it were a diode. there are transistors that don't test this way with a meter but nearly every HOT in a gaming monitor i've come across have worked/tested this way.
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I can't find Q704 for the life of me... found it on the schematic but can't physically locate the damn thing.
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Mark, try looking for it on the bottom of the board. Sometimes its easier to look there. A lot of times you can't see the numbers because of the component is in the way. :nerd:
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Mark, try looking for it on the bottom of the board. Sometimes its easier to look there. A lot of times you can't see the numbers because of the component is in the way. :nerd:
Hi Gary - I am. I have the main PC chassis out. Heck... maybe I should look at the top part?
I think I'm done for the night though. I might give one more crack when I get my laundry out.
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Looked and looked and looked. I can find all the Q's close to it, but not Q I'm looking for! :hissyfit:
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Looked and looked and looked. I can find all the Q's close it but not Q I'm looking for! :hissyfit:
:Scratch-Head: can you locate a large transistor near the flyback? try to get the part number off of it...the schematic shows Q704 as an SSS10N60 part number, maybe you can identify it that way? :banghead: :arrowthruhead:
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I did two nights ago. I looked up that number and just couldn't see it. In fact I looked up the part to see the configuration of it. I can try a forth time - maybe 4's a charm!
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I found a Q714 with that is a 10N60. It's on the big heat sync that goes around the flyback.
I do get a continuous beep on one leg.
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REPLY FROM kforman:
hey Mark! yippy you found the HOT!!! sorry it didn't match the schematics i provided, sent you on a bit of a goose chase. :duh: i was going to suggest you search the heat sink's around the flyback as the HOT is always mounted near the flyback on a large heat sink so good job sir!! :applause:
you can't do any harm by replacing electrolytic capacitors, i used to change any and all that i had good replacements for when i had a board on my bench whether they looked or tested bad or not. always remember to keep the microfarad value the same as the original cap but you can go up in voltage with no worries...e.g. old cap is 10mf/100V i would replace with 10mf/150V if i had it.
i would still suspect your HOT is bad, you could take it out of the board and test it again. i know it doesn't make sense but it's possible another component is causing a bad test in circuit.
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It's out of the circuit. And I still get a beep on one of the outside leads.
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I don't think that's the HOT, they are much bigger, like 5/8" wide and an inch tall
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Wish I knew what I was doing here... tempted to just pitch this in a dumpster.
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The UTC 10N60 is a high voltage and high current power MOSFET, designed to have better characteristics, such as fast switching time, low gate charge, low on-state resistance and have a high rugged avalanche characteristics. This power MOSFET is usually used at high speed switching applications in power supplies, PWM motor controls, high efficient DC to DC converters and bridge circuits.
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Looked and looked and looked. I can find all the Q's close it but not Q I'm looking for! :hissyfit:
:Scratch-Head: can you locate a large transistor near the flyback? try to get the part number off of it...the schematic shows Q704 as an SSS10N60 part number, maybe you can identify it that way? :banghead: :arrowthruhead:
The new transistor is in. I installed the CRT, powered up and got a steady, yet quiet static zaps. And I still had a black screen. I am 99.9% certain I got all the wires back in their spots. They all kind of fell in place.
Forget what I said about the static zap... the CRT wasn't fully plugged in! :banghead:
So now it's back to black. Again... the touch screen has power but there's no light in front where the video controls are.
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The CRT went to the recycling center. :pos_computer:
I put the touch screen control board on eBay and gave the plug from the chassis to Gary.
CRT problem solved! :propeller: