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Powering Multiple Princess Phones

Started by princessphone, January 02, 2014, 11:50:20 AM

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princessphone

Happy New Year!
Hi there, I'm a new member and thank you for allowing me to join. This is my first visit to a forum and I hope someone can give me some help or suggestions.
I've been cleaning up the old phone wiring in my house and being a big fan of the retro Princess phones, I thought of supplying supplementary power to several phone jacks throughout the house (to feed the light bulbs in the Princesses) by means of a single WE 2012A transformer, which I located near an expansion board in the basement.
This arrangement works fine with only 1 Princess phone no matter which location. However when a second Princess is added the lights dim by about 50% (more so with each phone added), even when all the handsets are down.
The 2012A is rated at 1.75 VA (about 0.2 amp), which is about the limit for a GE46 0.25 bulb. Therefore I replaced the 2012A with an Edwards 598 transformer 8V AC 20VA (2.5 amps). These are used to power door bells / chimes in buildings that run longer wire than in the average home. But the results are the same. A lot less light with more than one phone. The wire gauge varies between 24 and 22 which I think should be enough to carry the juice. This has got me really puzzled.
Installing a separate transformer for each Princess works OK, however I would like to explore the possibility or feasibility of a single power source.
Please give me your thoughts on this project.
Sincerely, John DeJonge
PS  Edwards also makes an industrial signal power transformer ( 8V AC 10 amp) but I would be scared and foolish to hook that baby up without a qualified electrician.

poplar1

Bell used a KS-16886, List 2 transformer for up to 10 "dial night light" (Princess) telephones. (A Trimline is a "dial light" telephone since it does not have a night light.) The 6.6 volts AC  output is 1.5 Amps.

Since the Edwards 598 is 8VAC 2.5 Amps, that is even greater than the KS-16886 L2. So the dim lamp problem may be the wiring. Are the jacks home run--i.e., an individual wire run from the basement to each location?

---------------------------------------------------------------------------------------------------------------------------------------------
Bell System Practices:
Section 501-136-100
Issue 3, June 1968

Table B, Note 2:

                               The KS-16886, L2 transformer is designed to power ten dial night light telephone sets and is not
                               recommended for single telephone installations. Do not use a common feeder where more than one set
                               may be off-hook at the same time. Home runs from each set to the transformer provide best illumina-
                               tion.

---------------------------------------------------------------------------------------------------------------------------------------------


"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

#2
This has been discussed in numerous threads here on the forum.
A search will turn them up.
I rememberer the following recent ones, which addressed the topic within at some point
*http://www.classicrotaryphones.com/forum/index.php?topic=10250.msg110642
*http://www.classicrotaryphones.com/forum/index.php?topic=10224.msg108723

There are several BSPs that address transformer aspects.
*BSP 502-701-100 Issue 1, February 1970
*BSP 501-136-100 Issue 7, November 1979

The 2012A transformer can only supply enough current for one Princess.  501-136-100 advises to use a KS-20426L1 transformer for multiple Princess sets. However, the L3 type was removed from service, because of problems.

I see, that Poplar1 just posted another solution.

poplar1

Also, 25 foot mounting cords (line cords) should not be used, at least not with a 2012A or 2012C. "The added resistance of this cord results in decreased illumination." (3.06)
"C'est pas une restauration, c'est une rénovation."--François Martin.

jsowers

Another thing to check--do you have the night light feature turned on? It operates when the handset is on-hook and could result in extra current drain and produce the results you described. It's also very hard to see it in the daytime. Just something to check. I hope you solve your problem, and welcome to the Forum!
Jonathan

dsk

Welcome to the forum  :)

To use a higher output transformer as you did seems right, but the increase of voltage may shorten the lamp lifetime.

If the wiring are shaped like a star, only one pair of wires carry the current to each lamp, and the voltage drop should not affect the other phones so much, if the wiring are going from one jack to the next etc. The voltage drop will affect the other telephones quite much.
In a domestic installation of 230V (Norway) the maximum voltage drop are 4% in hence to not affect the equipment used. If we allow about 10% the light intensity may decrease to a little over 50%, and 10% of 6 volts are only 0.6 volt drop!

That is actually the reason for using 50V on the telephone line, when the Local Battery phones used 3 volts.

Since the voltage drop not will be constant, you can not rise the voltage to much in order to compensate.

One way to do it would be to put in a source of 20-30V dc (transformer, rectifier no voltage regulator, but one fuse of e.g. 1 amp) and a voltage regulator in each jack e.g. one of these :http://tinyurl.com/pg3wtte

Today, this are a lo cost solution, but just not to ink about in the old days.

dsk

paul-f

Welcome to the forum, John!   ;D

We love to see photos, and would enjoy seeing and hearing more about your collection.

Do you collect the multi-line, message waiting and other variations of the Princess sets?
Visit: paul-f.com         WE  500  Design_Line

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