One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement the
heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that mode. I
could live with it that way, but being an engineer I'm sort of anal
about having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current
ratings of the "grain of wheat" incandescent indicator bulbs used in
those thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise working
thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working
bulb in our other identical thermostat, but I thought I'd ask here first.

Thanks guys,
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Jeff Wisnia writes:

One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement
the heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that
mode. I could live with it that way, but being an engineer I'm sort of
anal about having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current
ratings of the "grain of wheat" incandescent indicator bulbs used in
those thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise
working thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working
bulb in our other identical thermostat, but I thought I'd ask here
first.

As an engieer, doing the measurement will be unavoidable.

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"Jeff Wisnia" wrote in message
eonecommunications...
One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement the
heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that mode. I
could live with it that way, but being an engineer I'm sort of anal about
having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current ratings
of the "grain of wheat" incandescent indicator bulbs used in those
thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise working
thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working bulb
in our other identical thermostat, but I thought I'd ask here first.

Thanks guys,
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.


Jeff.. Why not measure voltage and use a LED? WW

WW wrote:
"Jeff Wisnia" wrote in message
eonecommunications...

One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement the
heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that mode. I
could live with it that way, but being an engineer I'm sort of anal about
having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current ratings
of the "grain of wheat" incandescent indicator bulbs used in those
thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise working
thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working bulb
in our other identical thermostat, but I thought I'd ask here first.

Thanks guys,
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.



Jeff.. Why not measure voltage and use a LED? WW


I could use a white LED, resistor (and prolly a diode across the LED too
since the voltage is AC.) But, as its taken 23 years for that first
incandescent bulb to burn out because it's probable it was designed to
run on the cool side, a replacement bulb will likely outlive me. G

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

On Thu, 13 Nov 2008 20:54:25 -0500, Jeff Wisnia
put finger to keyboard and composed:

One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement the
heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that mode. I
could live with it that way, but being an engineer I'm sort of anal
about having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current
ratings of the "grain of wheat" incandescent indicator bulbs used in
those thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise working
thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working
bulb in our other identical thermostat, but I thought I'd ask here first.

Thanks guys,

Does this help at all:
http://www.hvacmechanic.com/forums/r...ages/26276.htm

It looks like you may need a 24V bulb. AFAICT, the most common rating
appears to be 60mA.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

On Thu, 13 Nov 2008 20:54:25 -0500, Jeff Wisnia
put finger to keyboard and composed:


One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement the
heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that mode. I
could live with it that way, but being an engineer I'm sort of anal
about having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current
ratings of the "grain of wheat" incandescent indicator bulbs used in
those thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise working
thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working
bulb in our other identical thermostat, but I thought I'd ask here first.

Thanks guys,


Does this help at all:
http://www.hvacmechanic.com/forums/r...ages/26276.htm

It looks like you may need a 24V bulb. AFAICT, the most common rating
appears to be 60mA.

- Franc Zabkar


Thanks...The schematic of the thermostat in that link will be handy.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Jeff Wisnia wrote:

Franc Zabkar wrote:

On Thu, 13 Nov 2008 20:54:25 -0500, Jeff Wisnia
put finger to keyboard and composed:


One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
doing its thing and when the temperature setting is increased a few
degrees above ambient the auxillary heaters come on OK to supplement
the heat pump's output.

The blue "Aux Heat" indicator recently stopped lighting in that mode.
I could live with it that way, but being an engineer I'm sort of anal
about having everything working the way it was designed to.

Does anyone happen to know the type number or the voltage/current
ratings of the "grain of wheat" incandescent indicator bulbs used in
those thermostats. (It's soldered in.)

It would be annoying to spend good money to replace an otherwise
working thermostat just for the want of a bulb.

I suppose I could measure the voltage and current draw of the working
bulb in our other identical thermostat, but I thought I'd ask here
first.

Thanks guys,



Does this help at all:
http://www.hvacmechanic.com/forums/r...ages/26276.htm

It looks like you may need a 24V bulb. AFAICT, the most common rating
appears to be 60mA.

- Franc Zabkar



Thanks...The schematic of the thermostat in that link will be handy.

Jeff


I soldered in a new bulb yesterday. Tracing the circuit showed that
here's a single diode in the common return lead to both the bulbs in the
thermostat so the bulbs effectively see only half of the nominal 24 volt
AC supply.

I used a 12-14 volt "grain of wheat" bulb left over from my sons' model
railroading period of 20+ years ago and it worked fine.

Taking another closer look at the schematic in that link you gave me
shows the "arrow half" of the symbol for that diode, but it was very
easy for me to overlook. (And perhaps you too, since you thought I'd
need a 24 volt bulb. G)

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.98*10^14 fathoms per fortnight.

On Sun, 16 Nov 2008 12:17:08 -0500, Jeff Wisnia
put finger to keyboard and
composed:

Taking another closer look at the schematic in that link you gave me
shows the "arrow half" of the symbol for that diode, but it was very
easy for me to overlook. (And perhaps you too, since you thought I'd
need a 24 volt bulb. G)

Jeff

Yes, I missed it. But even if I had seen it, I would have still needed
to be told that it was a diode.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

On Sun, 16 Nov 2008 12:17:08 -0500, Jeff Wisnia
put finger to keyboard and
composed:


Taking another closer look at the schematic in that link you gave me
shows the "arrow half" of the symbol for that diode, but it was very
easy for me to overlook. (And perhaps you too, since you thought I'd
need a 24 volt bulb. G)

Jeff


Yes, I missed it. But even if I had seen it, I would have still needed
to be told that it was a diode.

- Franc Zabkar


But, I think I may have grabbed a bulb from the kid's model RR junkbox
that had a higher voltage rating than the 12-14 volts I thought it had.

Mentioning the successful repair to someone else got me a response that
running a 120 volt bulb off of 240 vac in series with a rectifier is NOT
equivalent to running it off of 120 vac without the rectifier and the
bulb will blow out rather quickly, because its filament is overvoltaged
quite a bit of the time.

I've got to think that one out a few more times before I'm ready to say
yes or no to it. Perhaps someone reading this post can pouint me to a
cite on the subject.

Jeff


--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Jeff Wisnia wrote:

Franc Zabkar wrote:

On Sun, 16 Nov 2008 12:17:08 -0500, Jeff Wisnia
put finger to keyboard and
composed:


Taking another closer look at the schematic in that link you gave me
shows the "arrow half" of the symbol for that diode, but it was very
easy for me to overlook. (And perhaps you too, since you thought I'd
need a 24 volt bulb. G)

Jeff


Yes, I missed it. But even if I had seen it, I would have still needed
to be told that it was a diode.

- Franc Zabkar

But, I think I may have grabbed a bulb from the kid's model RR junkbox
that had a higher voltage rating than the 12-14 volts I thought it had.

Mentioning the successful repair to someone else got me a response that
running a 120 volt bulb off of 240 vac in series with a rectifier is NOT
equivalent to running it off of 120 vac without the rectifier and the
bulb will blow out rather quickly, because its filament is overvoltaged
quite a bit of the time.

I've got to think that one out a few more times before I'm ready to say
yes or no to it. Perhaps someone reading this post can point me to a
cite on the subject.


There was a lot of discussion, and arguments on
news:rec.antiques.radio+phono a while back. Basically, a diode removes
one half the cycle, or applies power for half the normal time. you
have to multiply by .707 to get the equivalent voltage.

240 VAC *.707 gives an equivalent of 169.68, minus the .6 volt drop
across the diode, which leaves approx. 169 volts. Channel Master built
some B&W tvs with a 'dropping diode', and a series filament string
totaling 84 volts.


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