This model like most Hitachi sets will blank or shut the tubes off for a number of reasons----if you have sound the power supply etc is almost certain NOT to be the problem.
The first real question that will tell me something is do you see the filament in each of the 3 tubes light? This will tell me if the heater for each tube is up or not.
Reasons to blank the tubes: The set will instantly detect a loss of vertical or horizontal sweep--it will turn the tubes off to prevent instant screen damage to all of them. The set also monitors the screen voltage to each tube, and several other voltages--if any are MIA IT WILL BLANK ALL THREE TUBES.
I presume you do not get on screen display like the menu etc. What I need to know now is do the filaments in each of the three tubes light? You have to look closely to see this--each tube has a filament and if it does not light--that is the place to begin.
Tell me as much as you can so I have a real chance to help you--I know most of these sets very well as I have repaired hundreds of them--hands on experience with me--I try not to guess.
1.) With a voltmeter measure voltage on the green led's (each will go to an actual diode) to see which voltage is going down---the led's are there to indicate status of certain voltages.
2.) Do a visual look at the two convergence IC's on the large heatsink on the far right side of the set--STK-392-110 AND OR STK-392-150----look for any discolored or burnt resistors around them.
3.) You would have to gain access to the bottom of the main board: Look at I401---it is the vertical output IC--look for bad solder connections at it.
BEFORE I WOULD DO ANY OF THE ABOVE THERE IS ONE THING I WOULD DO FIRST--With the front grill off (the grill below the front screen) I would remove the inspection plate behind it and find the black block with 6 controls----you have to look closely at the block--3 are focus and 3 are screens--what I would do is locate the BLUE SCREEN control and with the set on slowly turn it up---if you get a full rastor(screen lit) with no video---the convergence and vertical circuits are ruled out--DO NOT TURN IT WAY UP--just enough to see what you have---if you see just a blue line left to right in the middle of the screen turn it instantly back down--that would point to the vertical circuit.
Read all this closely and BEFORE YOU ATTEMPT ANYTHING if you have questions ask me first.
SD TECH
Several possible ways to proceed now:
1.) With a voltmeter measure voltage on the green led's (each will go to an actual diode) to see which voltage is going down---the led's are there to indicate status of certain voltages.
2.) Do a visual look at the two convergence IC's on the large heatsink on the far right side of the set--STK-392-110 AND OR STK-392-150----look for any discolored or burnt resistors around them.
3.) You would have to gain access to the bottom of the main board: Look at I401---it is the vertical output IC--look for bad solder connections at it.
BEFORE I WOULD DO ANY OF THE ABOVE THERE IS ONE THING I WOULD DO FIRST--With the front grill off (the grill below the front screen) I would remove the inspection plate behind it and find the black block with 6 controls----you have to look closely at the block--3 are focus and 3 are screens--what I would do is locate the BLUE SCREEN control and with the set on slowly turn it up---if you get a full rastor(screen lit) with no video---the convergence and vertical circuits are ruled out--DO NOT TURN IT WAY UP--just enough to see what you have---if you see just a blue line left to right in the middle of the screen turn it instantly back down--that would point to the vertical circuit.
Read all this closely and BEFORE YOU ATTEMPT ANYTHING if you have questions ask me first.
That rules out video problem and maybe also vertical problem---
There should be up to 6 or 8 diodes around those led lights--make a list and start checking voltage on each when set is turned on---what you are looking for is one where voltage does NOT come up--if they all turn off but one or more turns off first look there.
Once you narrow it down to one or two of them with the SET UNPLUGGED check resistance to ground on the output side of the diode---there will be multiple voltages---one should be around 130vdc (volts DC) that one powers the high voltage and deflection circuits---on a high resistance setting it should not read less than 4,000 ohms and should climb.
The other voltages--two will go to the convergence circuit and be between 20 and 30 volts--one will be a positive voltage and the other a negative voltage--the convergence chips work with two voltages.
FYI: if the set has high voltage you should hear a whoosh upon turn on---20,000 plus volts should produce a sound you can hear--if no high voltage you have to look for the 130 volt line either not getting to the deflection board(horz output transistor).
You are getting closer to the area where the problem is.
The deflection and high voltage circuit develop high voltage to the 3 tubes; a 200 volt source for the screens to the tubes usually comes from there as well--large red wire on flyback delivers high voltage and a smaller red wire from there the screen voltage---you may have an open---for whatever reason the set may not be developing High voltage.
SD TECH
That rules out video problem and maybe also vertical problem---
There should be up to 6 or 8 diodes around those led lights--make a list and start checking voltage on each when set is turned on---what you are looking for is one where voltage does NOT come up--if they all turn off but one or more turns off first look there.
Once you narrow it down to one or two of them with the SET UNPLUGGED check resistance to ground on the output side of the diode---there will be multiple voltages---one should be around 130vdc (volts DC) that one powers the high voltage and deflection circuits---on a high resistance setting it should not read less than 4,000 ohms and should climb.
The other voltages--two will go to the convergence circuit and be between 20 and 30 volts--one will be a positive voltage and the other a negative voltage--the convergence chips work with two voltages.
FYI: if the set has high voltage you should hear a whoosh upon turn on---20,000 plus volts should produce a sound you can hear--if no high voltage you have to look for the 130 volt line either not getting to the deflection board(horz output transistor).
You are getting closer to the area where the problem is.
The deflection and high voltage circuit develop high voltage to the 3 tubes; a 200 volt source for the screens to the tubes usually comes from there as well--large red wire on flyback delivers high voltage and a smaller red wire from there the screen voltage---you may have an open---for whatever reason the set may not be developing High voltage.
Answers & Comments
This model like most Hitachi sets will blank or shut the tubes off for a number of reasons----if you have sound the power supply etc is almost certain NOT to be the problem.
The first real question that will tell me something is do you see the filament in each of the 3 tubes light? This will tell me if the heater for each tube is up or not.
Reasons to blank the tubes: The set will instantly detect a loss of vertical or horizontal sweep--it will turn the tubes off to prevent instant screen damage to all of them. The set also monitors the screen voltage to each tube, and several other voltages--if any are MIA IT WILL BLANK ALL THREE TUBES.
I presume you do not get on screen display like the menu etc. What I need to know now is do the filaments in each of the three tubes light? You have to look closely to see this--each tube has a filament and if it does not light--that is the place to begin.
Tell me as much as you can so I have a real chance to help you--I know most of these sets very well as I have repaired hundreds of them--hands on experience with me--I try not to guess.
SD TECH
Several possible ways to proceed now:
1.) With a voltmeter measure voltage on the green led's (each will go to an actual diode) to see which voltage is going down---the led's are there to indicate status of certain voltages.
2.) Do a visual look at the two convergence IC's on the large heatsink on the far right side of the set--STK-392-110 AND OR STK-392-150----look for any discolored or burnt resistors around them.
3.) You would have to gain access to the bottom of the main board: Look at I401---it is the vertical output IC--look for bad solder connections at it.
BEFORE I WOULD DO ANY OF THE ABOVE THERE IS ONE THING I WOULD DO FIRST--With the front grill off (the grill below the front screen) I would remove the inspection plate behind it and find the black block with 6 controls----you have to look closely at the block--3 are focus and 3 are screens--what I would do is locate the BLUE SCREEN control and with the set on slowly turn it up---if you get a full rastor(screen lit) with no video---the convergence and vertical circuits are ruled out--DO NOT TURN IT WAY UP--just enough to see what you have---if you see just a blue line left to right in the middle of the screen turn it instantly back down--that would point to the vertical circuit.
Read all this closely and BEFORE YOU ATTEMPT ANYTHING if you have questions ask me first.
SD TECH
That rules out video problem and maybe also vertical problem---
There should be up to 6 or 8 diodes around those led lights--make a list and start checking voltage on each when set is turned on---what you are looking for is one where voltage does NOT come up--if they all turn off but one or more turns off first look there.
Once you narrow it down to one or two of them with the SET UNPLUGGED check resistance to ground on the output side of the diode---there will be multiple voltages---one should be around 130vdc (volts DC) that one powers the high voltage and deflection circuits---on a high resistance setting it should not read less than 4,000 ohms and should climb.
The other voltages--two will go to the convergence circuit and be between 20 and 30 volts--one will be a positive voltage and the other a negative voltage--the convergence chips work with two voltages.
FYI: if the set has high voltage you should hear a whoosh upon turn on---20,000 plus volts should produce a sound you can hear--if no high voltage you have to look for the 130 volt line either not getting to the deflection board(horz output transistor).
You are getting closer to the area where the problem is.
The deflection and high voltage circuit develop high voltage to the 3 tubes; a 200 volt source for the screens to the tubes usually comes from there as well--large red wire on flyback delivers high voltage and a smaller red wire from there the screen voltage---you may have an open---for whatever reason the set may not be developing High voltage.
SD TECH