PVM-20M4A Power Supply Fault

This is another blog entry to detail what I did to fix a PVM-20M4. One night after playing some games I was in the process of turning everything off when something inside the monitor exploded and left the monitor lifeless. Since the monitor wouldn’t power on, the power board seemed like a logical place to look first and here is what I found:

This component is IC601 on the schematic – a STR-M6524. It’s a $10 part and replacements can be found on eBay. This fault seems like it is common and if you google around you can find others who have had the same thing happen. You cannot just replace this component, it will explode again (I learned the hard way). I found a Japanese repair blog that talked about what sounded like this fault and it suggested that when this happens two other components also fail – IC602 and Q501.

I pulled IC602 – a STR-S3115 and sure enough, pins 1 and 2 (V in and V out) were shorted together. I grabbed another one from eBay for $15 and replaced it:

I also decided that while I had the power supply board apart I may as well re-cap it just in case. None of them tested bad except C621 which might have been a bit out of spec. Also there’s a ceramic fuse that will also need to be replaced.

I used some arctic silver between the components and the heatsinks:

Q501 is located on the main board and to get at it you need to remove it. This means unplugging a lot of cables and sliding the board out – just take your time and label everything and you should be ok. This will require you to remove the anode cap so be sure to discharge the flyback correctly and don’t kill yourselves! It is a pretty big job and I didn’t want to do it again so I ordered one of Savon Pat’s cap kits to install while I had the board out.

Upon pulling Q501 out of circuit and testing it with a multi meter it was definitely faulty, there was short circuit between all three pins. Q501 is a 2SD1878 but a 2SD1881 has the same characteristics with a higher current rating so I upgraded this part, I was able to track one down from a local electronics supplier for under $20.

Here is where it lives on the board, I cleaned up the heat sink and installed the replacement with some arctic silver:

I installed the cap kit while I had the board out. If at first the solder won’t suck out add a bit more and try again, be very careful not to lift any pads. This monitor didn’t have terrible geometry before it failed but the the sides were a little wonky in places.

And the moment of truth, hopefully no explosions this time:

Lately I have been playing a lot of CPS2 and this monitor has been my daily driver for a couple of months. At this point I am fairly confident that the problem is fixed. I am not sure if the root cause was the transistor on the A board, the two failed ICs on the power supply or a dodgy capacitor. For anyone who has the same fault I would advise you to test all these components that I touched.

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