help for Trinitron kv-m1430a Dead
 

Hello everyone, a month ago the Trinitron kv-m1430a suddenly died, I use it to connect my old video game consoles, it has turned off and no longer shows signs of life, in fact the red standby LED is also off. 'I opened to try to understand what had happened to him and on sight there is nothing burnt, I started to do some measurements and first started from the fuse and it is ok, then I got to the 400 V 220 uf electrolytic capacitor and until there the voltages are present, then I went up to pin 3 of the transformer and they arrive 323 Volts, then to C 609 and from the diagram there should be 120 Volts but I can not find anything,
then I went to measure the voltages on the STR54041 which should be a voltage regulator and the measurements I made are all wrong, from what the diagram tells me.

Str54041
1: -17.2V
2: -17.2V
3: 187 V
4: -17.5V
5: -17.5

After various checks I managed to find a shorted component, D611 a zener R2M, I disassembled it, I gave voltage for a second and I saw that the TV led turned on, then I ordered a new R2M and replaced it , as soon as I switched on and blew the diode again. So I thought it might be the STR54041, I ordered the STR, I mounted it and just turned it on and immediately blew the 4 Amps main fuse, yesterday I reassembled the old STR and the original shorted diode to see if anything happened, as soon as I given voltage and jumped R601 from 3.3 ohm. I don't know what to do anymore, it's getting bad.😔

this is the electrical diagram

https://i.postimg.cc/5t2Rw7Kv/8-BC83...CE273-C7-C.jpg

Be sure you are using the right ground. There is a hot ground
in primary & cold ground for secondary voltages.
If you can put up the power supply schematic alone I may
be able to help more, its to small to read.

73 Zeno:smoke:
LFOD !

Hi, I thank you, I replaced all the electrolytics on the primary , and since I found the diodes bridge so much to remove my doubt, then I managed to find on another circuit I also have resistance from 3.3ohm 10 w, but just current the resistance is jumped immediately, I tried to measure the heads of R601 and there are 240V, I can't understand, there is a short circuit somewhere that puts R601 in parallel to tension of network . Whether it's all the fault of the str, the strange and that only Zener D611 jumped at the beginning.

This scheme should be more detailed

https://drive.google.com/file/d/1BPc...ew?usp=sharing

Service manual

https://drive.google.com/file/d/1RHf...ew?usp=sharing

Use the neg end of bridge for ground. It looks like they used cold ground
for the voltages !
R601 just to limit inrush current while big filter cap charges.
First be sure there are no shorts on the 3 secondaries The
120 V is most likely.
R602 & R607 give IC a kick start. If you dont get neg feedback to
that pin IC will blow. Open resistors will give "dead set"
R609 & R628 are the low end ( E ) of the IC's output. Over current will be seen here if a short on chassis & shut down the IC.
If IC isnt blowing you can monitor to see if IC is trying to start etc.
Unplug the DGS coil so it wont confuse you. Let us know how you do !

good luck
Zeno
LFOD !

Tomorrow I'll check what you said, then I'll let you know .

I can'taking measurements , every time I give voltage, it burns R601. I measured R602, R607, R609, R628 and they are all ok, I also checked all the diodes on the power supply and they are all ok
I isolated the three outputs of the secondary to measure the impedances of the transformer, it gave me very low values
18 - 14 = 1.9 Ohm
4 -8 = 0.5 Ohm
2 - 12 = 0.5 Ohm
not so if these values ​​are useful.
I have isolated all the outputs of the transformer T601, I have unsoldered D604 C608 C609 R612 R613 T604 and D611 but R601 keeps breaking as soon as I give voltage

Hope you have a variac.
Unsolder pin 3 of the IC.
Jump resistor & turn up slow from 0 VAC & watch the current.
Next would be unload one at a time the caps & semis off pins 3 & 7
of the transformer one at a time using variac as above.
I never had a switch mode transformer go bad BTW.

try that
Zeno

Hi, thank you, unfortunately I don't have a Variac. This afternoon I tried to unsolder SRT54041 and giving voltage R601 did not jump, could it be STR that causes the short and makes R601 jump?
I forgot to add that I do the tests on the tv with the Degauss coil disconnected from the circuit

Yes STR's do dead short. You can put an apx 75 watt incandescent
across the resistor. If its bright you have a short if dim no short. It MAY
blow the main fuse if shorted.

hi, i did as you told me, light bulb turns on, I tried unsoldering STR and light bulb does not turn on .
I think STR is the problem, I ordered a new one , New old stock

While the STR is out its a good time to recheck everything in the primary.
When you change it leave in the bulb & see what happens. If something
caused the STR to short that should keep the new one from blowing
HOPEFULLY ! Watch the caps. Sometimes they get a small crack but dont show
a short.

Zeno

ok thank you, I'll do as you told me, as soon as SRT arrives I'll let you know .
We hope that the problem will be solved .

Hello, the resistor has arrived, I did as you advised, I put the lamp on and unfortunately the problem persists, as soon as I turn on the lamp it flashes and you hear a small noise coming from the circuit with each flash, after a while the flashing stops and the lamp stays on, I checked D611 and R601 and they didn't jump, I don't know where to hit anymore.
https://youtu.be/di-S3QNFhsM
PS: the noise is not that loud it is the phone's camera that amplifies it.

We are getting to the place that I cant help much more remotely.
So I will give you a few more ideas.
Try to turn on a few times. Then feel the IC & Q802 ( hoz out )
They should be cool. You could also check the mains current, I
would guess it should be about 1 amp with DGS unplugged.

The light blinking looks like the supply is trying to run but sees over current
& shuts down. After that it tries to run again etc-etc-etc. Over current is
almost always from the Hoz out or HV.

73 Zeno:smoke:
LFOD !

Ciao, sorry, I was away for a while.
Today, I picked up the TV again after I had parked it for a while, I put the 60w bulb back in place of the fuse and I switched on, the bulb flashed and at the same time you could hear a ticking coming from the STR area, I approached and they felt like small electric discharges, I turned off I removed the latch and I moved the STR away from the heatsink and you will not believe it but the short was caused by the heatsink in contact with the STR, (I do not understand why it makes contact, I also put the fiberglass plate between the STR and the heat sink and the thermal paste for processors back on the STR before reassembling it) in fact as soon as I restored the voltage nothing jumped and the red standby light also turned on, I have to turn on the remote control but as soon as I try to turn on the red led goes out and the tube does not show signs, there must be some other problem caused by the first time I turned it on without the diode D611, I just don't know what, here any advice?

Slow ticking is usually a short on secondary.
Supply goes up then sees to much current so shuts off the
STR. Then it cycles again and again ...........

Can also be failing to go into "run". STR gets the on pulse but
not the run voltage. Voltage out goes up then falls. Again it can keep on trying.......

I will think about it & let you know if I have any other ideas.

73 Zeno:smoke:
LFOD !

Hi, I checked there is the output voltage from the secondary to the output of D604 and there are 128 V, I followed the diagram and it should go all the way to the flyback on pin 4, but nothing comes, so I saw that there is I think PS801 brokenis a 0.6A fuse shortly before it is blown, who knows why it blown, that blew it the day I turned it on without D611 ?

Good news, the fuses have arrived, I mounted it and luckily there is no other damage, it worked perfectly the first time I started it, I left it on for about forty minutes and it didn't give any problems. In the end, the main culprit was the failed STR. What I still don't understand why the CPU paste makes electrical contact between the heatsink and the STR, I have now put a piece of thermal pad in place of the paste.
Thanks again for the fundamental help.
https://youtu.be/QjD3pxM3GrI

The paste oozes out under torque and any high spots in the metal make contact...if the 2 surfaces need to be electrically insulated straight paste is never used in industry...It's always thermal pad or a paste, mica insulator, paste sandwich.

I didn't have any other pasta and then I thought it was okay, damn pasta made me crazy, it made me throw I don't know how many 3.3ohm resistors and fuses. It served me as a lesson.

Glad to hear you tamed the beast !
Last thing I always did was after the sets been on a while
feel the hoz out & the STR. Be sure they are cool enough to hold.
Then be sure there are no cold joints around the hoz drive & out.

Had fun working on the set with you.
73 Zeno:smoke:
LFOD !

Hi, actually the STR heatsink becomes very hot after about forty minutes, but the TV works fine, no strange noise can be heard coming out