On Mar 1, 5:11*pm, Jon Kirwan wrote:
On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold





wrote:
I've got a tankless electric water heater from eemax. that stopped
working the other day. *eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. *The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. *The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. *Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? *(60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. *(Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

Assuming the neon bulb is still okay, why not measure the
break down? *I'd start with perhaps 100k with your 240V. *If
the breakdown is around 100V, the current will be in the area
of 1mA, which is probably safe enough. *And 100mW, or so, so
you won't burn something up.

At say 2 watts, you would be talking in the area of 10k, my
guess. *Not 100 ohms.

Jon- Hide quoted text -

- Show quoted text -

Thanks Jon. This value seemed way to small to me too.

George H.