Megatron
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Jul 31, 2016, 3:22 PM
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CRT Samsung CB-528ZSE picture problem
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Regards,
I have problem with picture on CRT Samsung CB-528ZSE.
Here you can download datasheet manual:
http://www.electronica-pt.com/esquema/func-startdown/18703/
I'll put picture soon but this is what I found similar on google how the problem looks:
http://www.ussherpress.com/blog/wp-content/uploads/redscreen1.jpg
I had to turn G2 SCREEN voltage potentiometer almost on maximum to see something on picture.
It starts when I made an idiotic mistake when I measure the voltage on CRT PCB the voltage the probe slips and shorted on PCB connector MCT02 on a second when measuring pin3 175V shorted with pin 4 HEATER or shorted with pin 2 R, I don't remember, but it occur spark, and TV was shut down in stand by. When this occur the video transistor Q202 burned and I repleace it with the new one with the same mark KSA642 but it didn't solve the problem. The picture is now poor like the heater in tube is burned. I pulled of the PCB from tube and checked the heater on pins H1 and H2 and the heater seems fine, it shows on ohmmeter 2,6 Ohm.
I checked whole electronic elements on whole PCB motherboard and PCB on tube and found nothing. I desolder all transistors, diodes, condensators and checked with multimeter (trnsistors 6 way test, diodes 2 way test, capacitors with C-meter and electrolitic with C-meter and ESR meter.
I even repleaced all electrolitic capacitor and still no results. I checked all resistors and still nothing. I bought new videoprocessor IC501 TA7698AP and still no changes.
Here are results of measuring the voltage compearing with datasheet:
On CRT PCB connector MCT02 on pin3 the voltage is measured to high 196V instead 175V. On pin4 HEATER the voltage I measured is only 2V AC. Pin1 8,7V, Pin2 8,7V.
On repleaced transistor Q201 KSA642 on emiter I measured 8,7V instead 7,4 as on datasheet.
On vertical drive IC301 i have on pin9 24V.
On C457 i have 16,5V.
On main power supply transformer secondary I have after relay RL001 +33V, +125V(TP125), +18V, +5V.
On video matrix chip IC501 I measured on RGB output pins 20, 21, 22: 7,3V, 7,7V, 7,3V and I have 12V on CRT PCB connector MCT01 pin4.
On CRT tube connector RK, GK, BK: 195V, 195,2V, 195,5V
Sound is fine.
I realy don't have idea where to look for further and what causes the voltage on CRT PCB connector MCT02 to high 195V instead 175V, and heater voltage for my opinion to low only 2V AC?
Thank you
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Re: [Megatron] CRT Samsung CB-528ZSE picture problem
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