Maker Pro
Maker Pro

Citizen 27 inch color TV Model #C27401

Having big issues in solving this problem.
Power switch on this model is mechanical.
Here is the Problem.........
Push the power switch on and the red light lights up.
That's all.....
No High voltage, no audio, absolutely dead.
I checked the voltage reg....OK
I checked the HOT....OK
Checked ossilator HOT coil.....OK
Checked flyback......OK
Looked for cold solder joint....seems ok
Checked all power resistors...OK
Can't seem to find a schematic for this model either.
This TV is fairly new with hardly any use on it at all..
I checked with other techies in my area and they have a couple of these
TV's on their bench as well with the same problem...

I am stumped on this one.... :-(

I need some help on this one...
Any suggestions?
Thanks in advance
Michael Bearns
 
Jamie said:
Look for an onboard POWER RELAY, most likely in a black rectangular
case.
There was one very cheap TV, I once had my hands into that used the
heater of the CRT as part of the power supply. if that opened, it would
also not allow the power supply to start up. It was a good idea how
ever, bad CRT's many times would cause major problems else where when
things like ARC's took place.

Also, look for the degaussing circuit which is suppose to time out
and then switch on TV. It's been a while since I've really have had my
head into TV's. I've found not much profit in them. Just more of a side
line to help people out around me.
Thanks for the information jamie......
This TV does not have a relay.....
CRT heater is working......
degaussing circuit does time out......
 
J

Jamie

Jan 1, 1970
0
Having big issues in solving this problem.
Power switch on this model is mechanical.
Here is the Problem.........
Push the power switch on and the red light lights up.
That's all.....
No High voltage, no audio, absolutely dead.
I checked the voltage reg....OK
I checked the HOT....OK
Checked ossilator HOT coil.....OK
Checked flyback......OK
Looked for cold solder joint....seems ok
Checked all power resistors...OK
Can't seem to find a schematic for this model either.
This TV is fairly new with hardly any use on it at all..
I checked with other techies in my area and they have a couple of these
TV's on their bench as well with the same problem...

I am stumped on this one.... :-(

I need some help on this one...
Any suggestions?
Thanks in advance
Michael Bearns
Look for an onboard POWER RELAY, most likely in a black rectangular
case.
There was one very cheap TV, I once had my hands into that used the
heater of the CRT as part of the power supply. if that opened, it would
also not allow the power supply to start up. It was a good idea how
ever, bad CRT's many times would cause major problems else where when
things like ARC's took place.

Also, look for the degaussing circuit which is suppose to time out
and then switch on TV. It's been a while since I've really have had my
head into TV's. I've found not much profit in them. Just more of a side
line to help people out around me.
 
Jamie said:
Look for an onboard POWER RELAY, most likely in a black rectangular
case.
There was one very cheap TV, I once had my hands into that used the
heater of the CRT as part of the power supply. if that opened, it would
also not allow the power supply to start up. It was a good idea how
ever, bad CRT's many times would cause major problems else where when
things like ARC's took place.

Also, look for the degaussing circuit which is suppose to time out
and then switch on TV. It's been a while since I've really have had my
head into TV's. I've found not much profit in them. Just more of a side
line to help people out around me.
Thanks for the information jamie......
This TV does not have a relay.....
CRT heater is working......
degaussing circuit does time out......
 
J

Jamie

Jan 1, 1970
0
Thanks for the information jamie......
This TV does not have a relay.....
CRT heater is working......
degaussing circuit does time out......
Well, Have you check to see if there is any HV B+ at the collector of
the HOT ?
Open yoke and flybacks can also cause issues.
A lot of times, You need a feed back voltage from the flyback which
is normally a low voltage supply for the rest of the unit.
it's also used to insure power is good and keep the main supply on.
normally, a momentary flicker of this voltage will cause main supply
shut down.. Some times its simply bad caps at this section of the
unit and thus will produce a line pulse effectively the same as a transient
pulse that disables the main supply..

What you need to do is connect a scope to this and see if
you're getting a brief signal to the HOT Base and collector and
also look at any low voltage secondary taps for badly filtered
supply outputs that will show as a pulse on start attempt.




Happy hunting.
 
Jamie said:
Well, Have you check to see if there is any HV B+ at the collector of
the HOT ?
Open yoke and flybacks can also cause issues.
A lot of times, You need a feed back voltage from the flyback which
is normally a low voltage supply for the rest of the unit.
it's also used to insure power is good and keep the main supply on.
normally, a momentary flicker of this voltage will cause main supply
shut down.. Some times its simply bad caps at this section of the
unit and thus will produce a line pulse effectively the same as a transient
pulse that disables the main supply..

What you need to do is connect a scope to this and see if
you're getting a brief signal to the HOT Base and collector and
also look at any low voltage secondary taps for badly filtered
supply outputs that will show as a pulse on start attempt.




Happy hunting.
I have checked the yoke for opens.....OK
Flyback has been replaced.... No Change
All Caps are within their specs.... high voltage section.
B+ voltage is their as well.....
scope is being serviced and calibrated at this time, so this is not an
option.....
I am going to check the other things you mentioned tommorrow as I'm
getting eye strain. lol
thanks for the info.......
 
Does the remote work? had one of these with dead like yours and when
you pushed the button on with the tv set would not fire up but the
remote worked. once the set was turned on the switch on the tv would
work properly Mechanical Power switch on the tv was flakey
 
Power switch is working fine......
I have the remote as well and that is working as well.......
I checked what I could without a schematic.
Everything I did checked seem to be working....
I'm at my wits end......
From what I gathered this tv has only been on a couple of times and is
fairly new... I just can't figure this one out.... it might be a life
time project...LOL
-------------------------------
 
I doubled checked what you have said about the switch and remote.
Since I could not find a defective part in the TV set, Maybe I was
looking for the big picture, excuse the pun.
I tried one of my universal remotes on the set and randomly entered the
automatic scan from the remote that i had. bingo! the set came on.
I took apart the factory remote and the LED was broken off the board. I
resoldered the led and put fresh batteries in the remote and it works
perfectly. The switch on the tv does not turn on the tv. the switch is
used to put the tv on stand by mode so it can receive information from
the remote. I feel pretty foolish at this point and egg on my face. 30
years in the business and I get stumped on a simple problem/fix. I won't
forget this fix ever.

In conclusion, I thank you for the diagnoses on the remote, you were
spot on.

Problem has been solved and also would thank the others who had
suggestion for me in the repair of this TV.

Michael Bearns :)
 
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