Satlook Mark III repair

[fubar.gr]

They brought me a broken Satlook Mark III, which is basically a portable CRT TV with a satellite receiver and is intended for antenna installation technicians.

The first thing I realized was that the built-in battery ( it has a 12 volt UPS-style battery) was dead at just 1.5 Volts.

I took the dead battery out of the device and connected the cables to my bench power supply. As soon as I turned it on, it started to make a loud high pitched, alternating sound, so I turned it off immediately.

I then took it apart. There were two boards, the first having some voltage regulators and the other having the flyback and generally the crt control circuitry.

I looked for visibly blown capacitors or anything blown but did not see anything .

The CRT board had two TO-220 transistors on large heatsinks . I tested them off-circuit and they looked fine.

I removed the flyback from the board but I do not know how to test it. It has E176185 MC-FB-001 on it but couldn't find a datasheet.



Then, at the other board I saw something strange . It has several voltage regulators and I found their datasheets. But this one, while marked as VR2 on the board, the component (BUK555-100A) is actually an n-type MOSFET.



I thought that was simply a mistake. But I noticed that the third pin (source) is connected directly to the battery positive. This can't be right, can it?

Also, when this board is powered on it's own, it draws around 200mA. Isn't that too much?


So far I have the following questions :

1 ) How do I check the flyback? I do have a UNI-T 513 insulation resistance tester if that helps.
2) Is the MOSFET placed correctly there?

[Fraser]

2 comments from me....... LOPT failure unlikely on these units and best diagnosed in circuit. Failure usually kills the driver transistor and you lose power rails. And secondly.....I attach the schematics of the Satlook III for your use  Enjoy ..... they are pretty simple units



Oh and VR2 appears on the second schematic (Tuner) in the bottom right hand corner. It's part of the battery charger circuit 

[Fraser]

Just noticed on your picture of the LOPT......are those PCB feed-throughs still attached to the pins ? If so you will need to ensure that the pins are correctly soldered to the PCB on both sides otherwise you will have more problems to solve.

[fluxcapacitor]

Is there something missing above R126 .Can you check R67 ,R126 and R117 .