My KV27S42 is dead and red front led blinks 4 times when I plug it or switch ON then stop after 3 cycles (15 seconds). I replaced the IC541 with no success and I noticed that lots of voltages are missing (+13V, -13V, +135V and +200V on PCB A). I can hear the relay RY602 clicking and it supplies the 120VAC. I do not see any short between the +13V and -13V inputs of IC541 (pins 2 & 4) but when the multimeter is set to 20 Ohms, I can see the value increasing slowly, I think it is due to the capacitor between the inputs 2 & 4 of IC541, I did not check with IC541 floating. Resistances R561 & R562 are good with 0.47 Ohms.
I would like to jump the relay RY602 to achieve high voltages to see all functions working normally but it seems that all voltages are removed when the relay RY602 contacts close.
Any idea ?
I replaced Q502 on my Sony TV (KV27S42). TV started working after replacing Q502. I also used a good thermal compound. But few days later, it went to 2 flashing lights and now 4 flashing lights. Not sure what's causing repeat failure. Can anyone please help?
The +13 and -13 are generated by the flyback transformer as well as the 200 volts. the 135 is your B+ voltage and sould be there at start up. check the HOT and the Flyback. if there is no 135v check IC1751 on the C board sometimes if bad it loads down the 135v line. and can give a faulse vertical error.
horizontal output transistor (HOT) on IC1751 check for short between pins 4 and 6. pin 4 is grnd and pin 6 is vcc.
the pin lay out is 1=B in, 2=G in, 3 =R in, 4=gnd, 5= IK, 6=VCC, 7=R out, 8=G out, 9=B out
the transistor Q502 will show a short between Base and Emmitter but should not show a short between base and collector or emmiter to collector. if it shows short between either one of these then replace. also check for bad solder on T501 this can cause repeat failure of Q502.
T501 should be OK. 90% of the time Q501 fails on it's own. if you notice the transistor is on a large heatsink. the HOT is the most common failure in TVs because it is the hardest working transistor. they don't show heating normaly because of the heatsink. T501 sometimes have bad solder that cause Q502 to fail, just resolder it.
I ment Q502 not Q501
the vibration is from the deguasing coil as it demags the picture tube it vibrates the appiture grill inside the picture tube. this is normal and only happens at cold startup. all sony trinitron tubes do this and is not appart of the HOT (Q502) circuit.
onys you gave jaime867 the fixya did you mean to do that?
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I also have the exact same problem but mine is the 27V42....I think the circuity is almost the same. I tried replacing the IC601, IC1751, and IC541 as suggested in some of the posts but to no avail. I'll try to check the Q502 for short between B-C and E-C and possible replace it also. Interestingly, a month before my set died I get a loud vibration whenever I turn on the set. It vibrates the entire TV which last about <1sec but the TV will turn on. Not sure if this had anything to do with the failure.
If you already change IC1751, I would suggest to check IC601 on the power supply just to see if the voltage is getting to T603.
Try to disconnect and isolate lead # 2 from the FBT to be able to measure the voltages in the power supply circuitry.
Download the service manual if you do not have it yet.
Let me know if you need further assistance.
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Good info I will try this evening, but I have some questions :
what is the HOT ?
I know that the 135V is not there on power up like the other voltages, how can I check IC1751 ?
Good info I will try this evening, but I have some questions :
what is the HOT ?
I know that the 135V is not there on power up like the other voltages, how can I check IC1751 ?
I unsoldered IC541 to check for any short and it is not shorted. I checked Q502 and it is shorted on the PCB, I will remove it to make sure it is really shorted, also I want to remove R504 and R505 because I do not read 1 Omh for R505. I have some doubts with T501 (Transformer) as they is no reading on Pin 5 because of Q502 and also on Pins 1 & 3 on T501, what would the values for Pins 1, 3 and 6 ?
I have some very low voltages on FBT because of bad Q502 (?). I checked good IC501 (152V Pin 3 and 16.8V Pin 4). IC1751 no short on Pins 4 & 6.
thanks for your reply,
I finally unsoldered Q502 and it shows shorts between base and collector, base and emmitter, emmitter and collector, I am surprised that there is no sign of overheat on the PCB ! also the aera of T501 is clean. I think that I will remove T501 and check it appart.
I replaced Q502, resoldered T501, checked voltages, my TV is now working fine.
I noticed there was neither thermal compound on Q502 nor the heatsink. I put some.
Thanks Bobbyj !
I got the same symptoms you described with the vibration. If the circuitry is the same (do you have the shematics ?) go directly to Q502, very easy to test, if Q502 is not shored the power on the TV and check for different voltages (200V, 135V, +/-13V and 5V), they should be indicated on the drawings.
Acquired a KV27S42 and it worked fine. Two hours later after transporting home, it turns on and then off again by itself. The led blinks 4 times. What could have caused the sudden problem?
kv27v42 flashing indicator blinks 4 times. First just died. Turned TV back on, worked OK for 20 minutes. Now dead as a hammer.
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