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Sony plasma model PFM42V1 just clicks and buzzes continuing problems

I had previously written about this set. There was a "buzzing" sound
when turn on was attempted. The green front panel light comes on but
the set doesn't power up. I got into it and found that there is a
power supply board on the right side. This is where the buzzing seemed
to be coming from. There is a large heat sink lying flat which is on
top of what looks like a huge (perhaps 3.0 X 5.0 ") IC. The heat sink
runs warm.
There are two voltages marked on a connector on this board. There are
5.0 volt and 15.0 volt points evident. The 5.0 volts was OK but the
15.0 volt line was at about 9.0 volts. There was also a capacitor on
this board, C16. This is a 47uf 250 volt electrolytic which was bulged
at the top and had unreadable ESR.
I replaced the cap and the symptoms were the same. Within a minute or
so the new cap was running quite warm. I powered down and checked all
the diodes near this cap and they all seemed to be OK. The board was
reinstalled at this point so I don't know what the voltage across the
new cap was.
Since something was going on around the area of that cap my intention
was to briefly power up again and recheck these voltages. The set was
powered up for about 20 seconds and I had just finished checking the
low voltages when I heard a fairly loud "crack" come from the area of
this board. There was no smell or evidence of any component failure,
unless its that large IC under the heat sink which I can't really see
very well.
The buzzing is now gone and while the 5.0 volt line is still OK, the
15.0 volt line is now reading 12.0 volts. There are also two small
fans mounted on two other boards on this set that do not run.
Admittedly I may be in a little over my head here but I really don't
want to walk away from this kind of work, especially when these things
are so expensive and consequently so likely to have a repair estimate
Can anyone please offer some further assistance with this repair.
Sorry that this is so long but I don't feel its possible to provide
too much information when dealing with something like this. Thanks
very much. Lenny Stein, Barlen Electronics.