G05 Deflection board, transistors and heat-sinks

I'm afraid my electronics ignorance is going to show a little here: why is
it that some of the larger transistors on the G05-801's Deflection board
(Assembly 02-160005-01) have heat-sinks, and some don't?

Is it related to the amount of 'work' the transistor has to do, so the
harder it works the hotter it gets so the more heat needs to be dissipated?
Therefore it just depends which stage they are at in the circuit?

There are two MPSU57's and two MPSU07's on this board, all have heat-sinks.
However, the solitary MPSU03 and the two MJE253's don't have heat-sinks.
According to the schematics the two MJE253's (Q604 and Q704) should in fact
be MPSU57's, I haven't a clue why MJE253's were used, possibly because they
were available?

In case I have to replace these MJE253's (the board is faulty), I assume
that the MPSU57 equivalents/replacements can be used and that I won't need
to retro-fit any heat-sinks?

Thanks,
Phil

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Received on Tue Jan 8 02:27:50 2002