On Wed, 26 Jul 2006 18:52:00 -0400, "Michael" noreply@nospam put
finger to keyboard and composed:

In my case, varying the AC line input so that the DC input to the regulator
moves from 153 to 180V leads to an actual change of 5.8V on the regulator B+
line output (from about 130 to 135.8V DC). But there was less than 2.5 V
change between 156 and 180 V input.

I'm wondering if my observed variation in the B+ line is, in fact, normal
for this TV design.

The way I read Sanken's datasheet is that the output can vary by 2.6V
if the current is kept constant at 0.5A while the input varies from
153V to 180V. Alternatively, if the input is constant while the
current is varied between 0.25A and 0.5A, then the output variation is
only 1.0V. I also see a temperature gradient of 7.0mV/degC.

If the input is constant and the load is maintained at 7mA, then the
output is 135 +/- 0.8V.

The NTE1743 datasheet has similar specs for load regulation and
tempco.

Is it possible that your replacement part is made to less stringent
specs? For example, what if the zener reference were affected by self
heating? An ordinary zener diode with a voltage in excess of about
5.6V will have a positive tempco. This would cause the regulator's
output to increase with case temperature.

Is it possible that your replacement part is actually an STR3030 (=
NTE1742)? The STR3030 is a 130V regulator.

Try increasing the output voltage by replacing the diode at the common
terminal with a 4V7 zener.

- Franc Zabkar
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