Author Topic: Another Princess question  (Read 1465 times)

Offline Argyris

  • *
  • Posts: 25
Another Princess question
« on: December 26, 2015, 08:43:56 PM »
To get my Princess phone (Touch-Tone, 1971) to light, I wired a transformer directly to the light circuit. I didn't have an original Western Electirc transformer, so I used a random 6-volt power adapter I had kicking around, and it worked.

HOWEVER: I just noticed on one old document that the original WE transformers put out 6.3 volts AC. Is that really correct? Mine, like most "wallwart" power adapters, delivers DC voltage, and I do notice that the light is pretty dim.  Can anyone confirm that the old ones were AC?



Offline Phonesrfun

  • **
  • Posts: 4867
  • "Number Please"
Re: Another Princess question
« Reply #1 on: December 26, 2015, 09:07:40 PM »
The light doesn't care whether it is AC or DC.  The WE transformer is AC on the output.  You might measure your wall-wart voltage while it is powering the light.  If it is a small transformer, it might be loaded down to a lower voltage,
-Bill G

Offline Phonesrfun

  • **
  • Posts: 4867
  • "Number Please"
Re: Another Princess question
« Reply #2 on: December 26, 2015, 09:18:47 PM »
PS. The 2012 transformer is rated at 6-8 volts on its secondary with 110-120 on the primary.  So, with normal 120 volt service in a home, 8 volts is probably the more likely output. 


Also, when the Princess is on-hook and the switch is set to be a night-light, the lamp has a resistor in series and is intended to be dim.  When the phone is off-hook, it is intended to be brighter. 
-Bill G

Offline Argyris

  • *
  • Posts: 25
Re: Another Princess question
« Reply #3 on: December 26, 2015, 10:24:33 PM »
Thanks, Bill.  Will open it up and check the voltage draw with the light on. I will also look for a bigger transformer--there are plenty around these days.

The night light is dim to the point where it can't be seen through the dial buttons--it's just a filament glow that you can barely make out through the slots at the bottom.  I suspect that the resistor value has drifted upward with age.  I'll check that as well.





Offline andre_janew

  • **
  • Posts: 1601
Re: Another Princess question
« Reply #4 on: December 27, 2015, 12:56:35 PM »
Also, if you have a 9VDC adapter, you may want to try it as well.  The extra voltage probably won't burn out the bulb because it most likely won't have enough amperage to do so.

unbeldi

  • Guest
Re: Another Princess question
« Reply #5 on: December 27, 2015, 01:13:59 PM »
We discussed the electrical specifications and measurements of the 2012A or C transformer and the lamps in the Princess in detail in the past.

The original transformer is rated at 1.75 VA, so at the rated filament current of those lamps (250 mA) it outputs exactly 7 volts.   The #46 lamp is rated at 6.3 V, IIRC, (or its GE replacement)   The transformer is selfprotecting, and has an internal impedance of 50%.  This means it outputs ca. 14 volts without a load, but that doesn't mean one can use a regulated DC supply of that voltage. Other transformers must be current limiting to the specs of the bulb.
« Last Edit: December 27, 2015, 01:21:28 PM by unbeldi »

Offline andre_janew

  • **
  • Posts: 1601
Re: Another Princess question
« Reply #6 on: December 27, 2015, 04:07:02 PM »
So, I figure 9 volts at 195 mA shouldn't be a problem.

Offline TelePlay

  • Global Moderator
  • *****
  • Posts: 7251
    • . . . times keep changin'
Re: Another Princess question
« Reply #7 on: December 27, 2015, 04:20:28 PM »
So, I figure 9 volts at 195 mA shouldn't be a problem.

Just curious, what has 195 mA, or in other words, where did you get that number, or, why are you using that number?

Offline andre_janew

  • **
  • Posts: 1601
Re: Another Princess question
« Reply #8 on: December 27, 2015, 04:31:58 PM »
Volts times amps equals wattage.  Wattage divided by volts equals amps.  (7 volts x 250mA = 1.75 watts)

Offline TelePlay

  • Global Moderator
  • *****
  • Posts: 7251
    • . . . times keep changin'
Re: Another Princess question
« Reply #9 on: December 27, 2015, 04:49:42 PM »
So, I figure 9 volts at 195 mA shouldn't be a problem.

Just curious, what has 195 mA, or in other words, where did you get that number, or, why are you using that number?

What I meant was, what lamp are you using that has a filament current of 195 mA? What lamp is rated 195 mA?

Offline Argyris

  • *
  • Posts: 25
Re: Another Princess question
« Reply #10 on: December 30, 2015, 04:49:23 PM »
For the record, I just decided to go ahead and order a WE transformer (it cost me a whole five bucks), and the bulb is brighter now. Problem, such as it was, solved. Original equipment!