PANASONIC TX-28LD4F SUDDENLY IN STAND-BY

1sr124-4at82

I have a problem with a panasonic TX-28LD4F television.
During some minutes it works correctly, but suddenly it is put in Stand-by.

I think the problem is in power supply, but I´m not sure.

Somebody could help me? please.

tx-28ld4f

I've got a PANASONIC TX-28LD4F with a simillar fault but I am really lost!
When I Switch the TV ON, the EHT starts but the TV goes to standby in 4 seconds. My suspect is around the EHT transformer.If I found the fault I will contact you I hope you do the same.

tv goes to standby

I found the problem in soldered joints of vertical IC.
Resolder them and that is all.

panasonic tx-28ld4f

I already resoldered some dry joints on the vertical IC and the set worked fine for 2 weeks. Now it's with the same original symptom.

tv panasonic quintrix tx-28ld4f

I think that the problem is the same one, because the set worked correctly during two weeks.
In any case. Have you watched if the high voltage transformer is good?

panasonic lcd tv standby fault

I have got the same problem,it rectifaied. it was the problem with CRT. please connect the chasis with another tube for confermation..

Thanx

pulgadas de panasonic tx-28ld4f

I have found the defective parts,but don't know the value of the zenerdiode yet.
R559 (0,33 ohms) is open and diode D558 is shortened.

Added after 35 minutes:

the diode can be replaced by a BYD33W and the resistor is a 0,33 ohms/0,5watt.

panasonic crt low standby voltage

The original part number is:
D558 1SR124-4AT82
R559 ERQ12HKR33

D558 is not a zener diode

riparazione panasonic tx-28ld4f

it is all very well to replace the 'faulty' components

BUT why did they go wrong

usualy further along you find a resoviour cap
that has gone dry but may 'appear' to be ok

so what i do is this

first replace all dodge looking {meter / visual or smell the base if you can smell it it is gone.....}
electrolytics bigger than 47uf electrolytic caps in tv's older than 7 years or certain models that are known to run 'hot'

then change the line driver transistor anyway
as it will be stressed

and also any poly caps near to it if they have burning swelling etc...

these faults are caused by bad timing of the switching psu or ht driver stages

caused by drifted caps or stray capacitance shorted turns on transformers etc


or more often a cracked or gone brown 400v ceramic coupling cap near to the line output transistor

that diode sounds like it provides an LT rail
look to the vertical frame driver section .. driver ic


the way to tell with the poly types is to remove them and look for the tell tale burn on the pins or pin on the underside
you can look all day and never find this fault

unless your methodical

another way these timing faults can be caused is
1} shorted turns on the lopt's low or high tenssion turns
2} bad poly caps caused by excessive node voltage when one of the linearity coils has a shorted turns
{black transformer has just one winding not your usual transformer but a high Q choke if it goes wrong the voltage and current nodes and antinodes move around to different places in the circuit and can be much enhanced and impure }

3} excessive voltage or under volts /bad waveforms {triangle wave instead of dc} from the psu usualy caused by low value dryed up electrolytic caps near to switch mode driver ic

most faults can be traced to a bad high voltage poly or to an electrolytic
in the psu or the lopt linearity or purity sections
{shrunken sleaving on electrolytics or there smell is a good indicator}



i hope you find the real issue before you buy a new one

and dont forget to resolder fully all parts esp the plugs and connectors
and pins of the ht poly caps {as they turn to carbon slowly if the nodes move}

DO THE WHOLE REPAIR AT ONCE AS A SERVICE SHOULD BE

hehe