Dear Badcaps staff,
this Hp MX70 crt monitor has the chassis Lite-On C1770NSL. In this video you can see the problem.
Here's the schematich.
There are 53V at pin 2 of Flyback Transformer (FBT) when the monitor is off.
There are pulses up to 250V at pin 2 of FBT when the monitor is on. In this situation there is no voltage coming out from pin 4 of FBT.
Transistor and diode are not shorted or opened.
There are 4 N-ch mosfets, all ok.
I've checked with an LCR meter some polyester capacitor near the FBT, they are good.
The voltages 80V, 59V, 11.6V and 7V are ok.
There are horizontal drive pulses.
The one coming from pin 8 of IC401 TDA4841 is not stable in amplitude, but don't know if this is the cause or an effect.
The other two pulses coming from pin 15 and 29 are stable (TDA4841).
All the electrolytic capacitor have been tested.
The entire board and crt board have been resolded.
I think I'll do the lamp test removing the 424 resistor (base of Q402) and connecting the lamp to C and E.
because I'm too lazy to remove Q402 again.
Can't find the solution.
Thank you for reading.
Feel free to suggest some test to do.
this Hp MX70 crt monitor has the chassis Lite-On C1770NSL. In this video you can see the problem.
Here's the schematich.
There are 53V at pin 2 of Flyback Transformer (FBT) when the monitor is off.
There are pulses up to 250V at pin 2 of FBT when the monitor is on. In this situation there is no voltage coming out from pin 4 of FBT.
Transistor and diode are not shorted or opened.
There are 4 N-ch mosfets, all ok.
I've checked with an LCR meter some polyester capacitor near the FBT, they are good.
The voltages 80V, 59V, 11.6V and 7V are ok.
There are horizontal drive pulses.
The one coming from pin 8 of IC401 TDA4841 is not stable in amplitude, but don't know if this is the cause or an effect.
The other two pulses coming from pin 15 and 29 are stable (TDA4841).
All the electrolytic capacitor have been tested.
The entire board and crt board have been resolded.
I think I'll do the lamp test removing the 424 resistor (base of Q402) and connecting the lamp to C and E.
because I'm too lazy to remove Q402 again.
Can't find the solution.
Thank you for reading.
Feel free to suggest some test to do.
But today, I’m making an exception here. Why? No idea. Perhaps only because the repair details are still “fresh” in my head… which is ironic, given this is a 16 year old monitor that hardly anyone will care about today. It is new to me, though. 
I picked it up last November from someone on my local Craigslist. It wasn’t very close to where I live, but was close to a family friend that I had to go visit anyways. So after watching the posting on Craigslist for a few weeks and seeing it getting...
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