MAG DJ530

[bill]

I've got a MAG DJ530 monitor that suddenly crapped out. The standby
circuit appears to be functioning, as when I depress the momentary on
switch the front LED lights for about a half a second, and the relay
clicks. But it shuts down immeadiatly. I can keep depressing the on
switch and it will keep up the same pattern. It SOUNDS to me when it
tries to start that the main power supply MIGHT be overloaded (i.e.
there is a short somewhere) but it's hard to tell (by ear anyway).

I have tested just about every semiconductor on the board, including
the HOT and several MOSFETs, everything checks out clean (I tested
them out of circuit, with a professional tester). I have checked and
double checked all DIODES. I ESRed all the capacitors and found a
couple that were bad (or borderline) but it still did not make any
difference. I removed the HOT and it does the same thing. I have
been over the board several times with a magnifying glass and I can
find no evidence of any burnt components. The board has a 7812
voltage regulator whose soldered connections were heat cracked, so I
resoldered them and no difference. Then I replaced the 7812 just to
be sure with a known good one and no difference.

Anyone have any suggestions? It's my own monitor so I don't mind
spending the time on it, but I'm only willing to put another couple of
hours into the project before I relagate it to the spare parts bins.

Thanks

-Bill

 

[Jerry G.]

Is the power supply fully verified that it is working correctly?

Are there drive pulses coming from the scan generator, to the various scan
stages?

Is there proper drive to the HV generator, if it is separate from the
horizontal output stage?

Are the safety or protection circuits properly verified.

A long while back, I serviced some monitors that are similar to the one you
have. I have had number of them where the flyback has failed.

--

Jerry G.
======


<bill> wrote in message I've got a MAG DJ530 monitor that suddenly crapped out. The standby
circuit appears to be functioning, as when I depress the momentary on
switch the front LED lights for about a half a second, and the relay
clicks. But it shuts down immeadiatly. I can keep depressing the on
switch and it will keep up the same pattern. It SOUNDS to me when it
tries to start that the main power supply MIGHT be overloaded (i.e.
there is a short somewhere) but it's hard to tell (by ear anyway).

I have tested just about every semiconductor on the board, including
the HOT and several MOSFETs, everything checks out clean (I tested
them out of circuit, with a professional tester). I have checked and
double checked all DIODES. I ESRed all the capacitors and found a
couple that were bad (or borderline) but it still did not make any
difference. I removed the HOT and it does the same thing. I have
been over the board several times with a magnifying glass and I can
find no evidence of any burnt components. The board has a 7812
voltage regulator whose soldered connections were heat cracked, so I
resoldered them and no difference. Then I replaced the 7812 just to
be sure with a known good one and no difference.

Anyone have any suggestions? It's my own monitor so I don't mind
spending the time on it, but I'm only willing to put another couple of
hours into the project before I relagate it to the spare parts bins.

Thanks

-Bill