right,this needs some explanation,i'll abridge it a bit,it still might look like a novel to some
the original and real reason the tv died was a protection diode,just after the 120 volt rail on the secondary side of the power supply,its sits between that rail and ground it was dead short,not its part of the power supply
previous owner replaced the switching regulator on the primary side of the supply,this was installed without a sil pad(i'll get to that in a minute) which introduced a dead short on pins 3 and 4,pin 3 connects internally on the regulator to the heat spreader on the ic,pin 4 is connected to the heatsink
a sil pad is a insulation pad that goes between the two part to electrically insulate them,but allow some heat transfer,moving along
pins 3 and 4 intern are connected directly to the mains rectifier dc side,which blew the fuse
inspection of the board,previous owner removed all the capacitors,to check and then reinstall them,this led to lifted/broken pads and broken missing traces,it happens sometimes but not to this extent,while im checking this i noticed some capacitors where put in the wrong locations,triggering me to check them all,there are over 50 and tidy up a bit
i also noticed the fuse holder,is slack,it doesnt really hold the fuse tightly,it sortof suggests it had a few fuses installed and was power cycled,i can just alter the tension with some pliers it needs to be tight
one connected wasnt connected to the board broken traces etc
parts replaced to make the supply work
r2m protection diode,reason for replacement,its dead jim
str54041 replaced due to the way it was installed
4 amp 600v bridge rectifier,due to having a dead short being apllied to it on tis output,it didnt test bad,but i dont know how many times a fuse was rpelced and power cycled,due the fuse holder being loose,not any chances
4 amp fuse
power on test shows power supply if prefetly fine,but no picture,yes there is more faults
after some fault finding and ilimination,turns out there isnt any horizontal drive,traced this back to the ic that generates the pulses,its not there,two options,its either the chip or its not got power,it turns out,its power,there was a broken trace to the ic,this fault was introduced by the previous owner,it was a lifted pad
now we have a picture not a nice picture but its there,but there are still faults
it had a early start a vertical problem so i recapped the vertical output,problem solved,this was already there i think before the tv died at first,there is another fault
it had a sync issue,that couldnt be just tweeked out,after having a think,it was either happening at the source where it comes into the tv,or at the horizontal sync adjustment area
the effect on screen is a distorted top part about an inch or so down
since both areas,is just a total of two capacitors,i just went ahead and did both,problem gone
i bit of time spent tweeking pots to try to make the picture as good as its going to be,etc
there a bit more to it than that,but im trying to keep this short,beleive it or not
i dont normally do writups,but this i thought needed some explanation in some form
i think thats about it,final conclusion: some strange decisions were made
some pictures to show it works,tv was made in 1993 going ic date codes,its mono,pal only has rgb through scart etc,and basic remote,white case,dont see that very often
it has a interesting way it goes into standby,power supply does not turn off,it simply turns the horizontal drive off or on,my suggestion is to turn it off at the mains switch on tv when not in use
