7 Nov
2014
7 Nov
'14
9:37 p.m.
, I would want to reduce the number of variables.
If it doesn't work
with an MJE13007, then what? Is it that this transistor is not suitable, or is there some
other
fault?
That's why god made oscilloscopes, Tony :) But really, a well-designed If an MJE13007 doesn't work, try another. If not
that, try, say, a
BU406. I seem to recall that some early Macs would work with an
MJE13007 just fine, but others of the same model required the BU406.
In other words the transistor can be critical.
Personally, I don't think that Zenith would ever make the mistake of
requiring selected semiconductors on what is essentially the video
section of a TV set, something that they made in the millions. The
service manual for the DT2 certainly makes no mention of it.
Hmmm... Not a horizontal output stage, but I have bitter memories of the PSU
in a Zenith MDA monitor. This darn PSU combined the reliability of a switcher with
the efficiency of a linear (!). It was a free-running (no regulation) chopper stage
feeding
a chopper transformer. The output of that was rectified/smoothed and gave about
20V DC. It was then regulated down to 12V for the monitor by a discrete transistor linear
circuit -- the reference voltage didn't come from a zener diode, it was the drop
across the
green power-on LED.
Anyway this thing would eat choppers. Sometime it would run for a few minutes and then
the
chopper would short. I finally found _a_ transistor that lasted. I could find no other
faults (caps
and diodes all OK or replaced, transformer rang OK, etc). I concluded the original
transistor had
been selected for something-or-other.
Does your DT2 manual give the industry standard number or just the house number for the
HOT? If the former, then sure, it's not selected. If the latter, it may well have
been.
And no, a failed HOT is not going to do more damage to the monitor. It might to the
OP's
(in)sanity, though :-)
-tony