Phil Allison wrote:
"Dave"

Have a very small (5" screen) black and white TV that has lost its
verticle hold.

** Verticle ???

It is not a faulty power transistor in the vertical output - or
their would be no pix at all.

MIL would like it repaired if possible,

** MIL ?

Is there a fourth letter missing .....


and kept in storage in case of another hurricane knocking out power
and services like the last one did. Upon opening it up I see a power
transistor (2SB834) with signs of overheating. My meter tells me
that the E/B and B/C pn junctions are switching at .574 and .572
volts, respectively. Am I missing the mark, or does this sound a
little low to others as well, as if the pn junctions have been
damaged?

** Sounds normal to me.

Its a few more minutes until my candy store opens, and several hours
before I'll be able to get by there, but to me, this transistor
souinds like a good candidate for replacement. Would appreciate
hearing what others think, if anyone cares to comment. Otherwise
I'll bide my time until I can prove the part one way or another. Just
hope I don't have to order the damn thing and wait a week.

** Loss of vertical HOLD is far more likely to be a fault in the
small signal circuitry OR the power supply.

Can you still adjust the vertical frequency to get the picture
viewable - but rolling ?

The first thing to check is all the filter and coupling electros in
the vertical and PSU for the vertical.

You need an ESR meter or lotsa luck.


.... Phil

Phil is correct. The vertical output isn't likely to be the problem. Look
specifically in the sync separator and vertical oscillator areas for your
problem. The vertical oscillator isn't being locked to the vertical sync
pulses. That's why the picture is rolling.
Of course, the first thing to check is the power supply voltages and ripple
in those circuit areas. Clean power is essential to proper operation of any
circuit.
--
David
dgminala at mediacombb dot net