Acer 7254E CRT Monitor

[senz_90]

Okay, got this monitor for free and I think to give it for my friend those are lack of money to buy a monitor if I could repair it.

the problem is led indicator blinking and no high voltage on screen (try to feel it with my back of hands).

I am trying to troubleshoot it but it stuck my mind and I want to ask some advice to help me. what I've done is measure voltage on mains caps and got about 260VDC (looks normal), try to measure UC3842 IC Vcc pin get about 12VDC fluctuate (jumping up and down) on my analog VOM needle, very small dc voltage fluctuate on all secondary diodes. No voltage to HOT. it looks a fault laying on primary section, but none are checked failed !! I have try to replace the IC and the mosfet is fine but still no result.

HOT were checked fine too.
I am trying to isolate the problem by remove smps transformer as jestine smps book, and get not flicker on my vom. I am sure the problem is on primary but when I try to remove secondary diodes one by one, I found one diodes that lead to vertical IC makes the led stay on when removed from the circuit. I try to changes all caps on primary section except the big one and 0,22uf ones, also one caps to vertical IC and no result.

I have measure the smps transformer with ring tester and get 4 ring (led lamp) lit on my tester. Is this looks defective?

Any sign or ideas? any help would be very appreciated. and I will attach some photo if needed. thanks.

[senz_90]

Re: Acer 7254E CRT Monitor

fixed !! i have try measuring horizontal section since this secondary diode is connected to vertical ic as flyback generator from reading on datasheet. I have think the problem maybe on the primary but this secondary diode test shorted to ground. I am miss something when measures horizontal section before.
This time i am find b+fet irf630 was shorted and yes it's true after removal from the board and now the secondary diode didn't shorted anymore. the other pairs of fet acts as buck or boost regulators ( didn't sure enough) were checked fine. changes it and worked likes a charm !!

[selldoor]

Re: Acer 7254E CRT Monitor

Well done!!
Not many hands on crt members about- mostly in the US so you probably missed the time slot for help. I know nothing about crt and few people want them these days -often difficult to even give them away, here.

[senz_90]

Re: Acer 7254E CRT Monitor

Well done!!
Not many hands on crt members about- mostly in the US so you probably missed the time slot for help. I know nothing about crt and few people want them these days -often difficult to even give them away, here.

thanks !!
in my country there are still many crt tv and monitor repairer because we still have many household using a crt tv and monitor due to economy factor, not likes europe or usa or others wealth country. I have even hear this "if broken just trash it and buy a new one". this makes repair shop have to struggle from bankrupt? who knows.

after 2012 years the price for led or lcd tv/monitor decreases rapidly and become popular but i am still wanna get an experience and satisfy my hobby to repair broken things.
I would happy to live on europe or usa and my house will full of saved crt tv and monitor. LOL