Background, I'm new to Agoraquest.com. I signed up so I could get help with my Wega KV-36XBR450 that shutsdown and blinks 5 times. I've done electronics classes before so I can solder and unsolder ic chips, and am a pc technician. I have a few questions below, before I undertake this task. Any help would be most grateful as I intend to do it in the next week or so. I'm a real newbie at this!!
2) I have the service manual but I'm not good at reading complex circuit board diagrams. But at the beginning of the manual it shows how to disassemble a the tv and flip D-Board & A-Board from horizontal to vertical service position.
I assume these are the two boards that have the 3 ICs I mentioned in question 1
3) As this is the first tv I've opened, I don't want to kill myself by mistakenly touching some high voltage transformers/capacitors. What should I avoid?
I read the part about shorting the anode and coated ground earth strap, but I'm not sure how to do that or if its even necessary. The tv has been disconnected a week now so will that mean any voltage is drained out???
4) When I take the tv back cover off will the tv be very front heavy and fall forward?
I'm just going to try swapping out these chips as a last ditch effort since they aren't an expensive fix.
1) Yes, all three of those ICs are the MCZ3001D type. (You can also use the MCZ3001DB, which some have speculated is an improved version of the MCZ3001D)
2) Yes, those are the boards in question. Most people just replace one or more of the ICs on the D-Board. I wouldn't bother with the IC6001 on the A-Board unless the D-Board IC repalcements didn't correct the problem.
3) I would leave it unplugged and also be careful about what you touched. That's what I did and I never had a problem. But I think the TV can hold a charges for quite a while. Maybe someone else can comment.
4) It won't tip over if it's on a flat support. But it won't take much force to tip it over forward. So just be careful.
ad 1) : The IC with the suffix -B is an improved version of the MCZ3001D.
ad 2) : Most (!) Trinitron CRT's are IBR types. IBR means Inner Bleeding Resistor and this refers to the resistor which is inside the CRT and is used for horizontal static convergence (H-STAT). If there is a potentiometer near the CRT-socket which is marked H-STAT, the combination of this potentiometer and the IBR will discharge the high-voltage residing on the CRT within half a minute. So if there is such a potentiometer, the high-voltage is no problem.
Second problem is remaining charge on the large smooting capacitors in the power supply. Especially when a switch mode power supply is not driven (eg. due to a defective driver IC such as the MCZ3001D) it is possible that the used smooting capacitor retains its charge vfor a long time. If this is true depends on the design of the circuit. In most cases the start-up resistors of the driving IC works as a bleeding capacitor, but that's not always.
So it is a good habit to check all "big" capacitors with a voltmeter, or discharge them using a suitable resistor to be absolutely sure. (Keep a 1 kilo-Ohm / 1 Watt resistor across the pins of the capacitor for aproximately 10 seconds, using an insulated plier.)
If you can post a photograph of the power supply board(s) here, or send it to tv(at)techie(dot)com I can point out which are the "dangerous" capacitors.
Stupid question, but how do I remove the rear cover, I've unscrewed the 20 screws as per the manual. But they say nothing about pulling or twisting the cover off, and it seems to be still solid when I try pulling back with a buddy holding the front.
You might have to pivot/tilt the TV forward a bit in order to take the TV's weight off of the bottom of the plastic cover. Do this carefully as the TV is "tube heavy" and it's prone to tiping over forward. I needed to do this with my KV-36XBR400. Good luck with your repair!
Maybe they used one-side adhesive felt on one part of the cabinet to avoid mechanical resonance. If such a rear cover was not removed for a long time, this could be sticky. The trick then is to gently force a small gap at one of the corners and from there to "separate" both halfs.
By the way: This does remind me the early days of servicing TV's. We went out for a service call to a Sony KV-1810E with a convergence error. This 1973 model had a wooden cabinet with a plastic rear cover. We removed all screws to remove the rear cover, but how we tried, the rear cover could not be removed. We tried to push a screwdriver between the rear cover and the cabinet, but no luck. We asked if the set was serviced before and told the owner that somebody must had glued the rear cover, for any unclear reason. We took the set to our workshop, and after a telephone call with the Sony representative it turned out that there were also two screws at the bottom of the set which has to be removed, and after that the complete cabinet and rear cover assembly could be removed.... http://www.circuitconcepts.nl/kv-1810e.htm It's not a pity that technology has changed in the meantime. These models used some Sony-specific parts (SG-613 Gate Controlled Switches) in the power supply unit and the horizontal deflection output. When something went wrong, these parts were the first to blow.
Thanks for the help, but I just have no time to tinker around with the tv. So I've passed it on via freecycle and will email the recipient this forum.
If he has any questions, I hope you can extend your knowledge to him as well. Thank you and God Bless
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