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Letting go...

Started by Sargeguy, December 05, 2013, 09:59:17 PM

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Sargeguy

That's what I figured.  The sidetone does not bother me, I think it's actually sort of interesting to point it out when explaining how old phones performed. 
Greg Sargeant
Providence, RI
TCI /ATCA #4409

unbeldi

#16
.

poplar1

#17
Another reason for having two capacitors instead of one:
A capacitor that could withstand the high ringing voltages required heavy insulating paper. Because of the physical size required, it was limited to about 1 MF. By changing to two capacitors, the talk capacitor could now be 2 MF with lighter insulation.

(Ralph O. Meyer's Old Time Telephones, 2nd Ed., page 113)

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

poplar1

Quote from: Sargeguy on December 10, 2013, 01:40:07 AM
That's what I figured.  The sidetone does not bother me, I think it's actually sort of interesting to point it out when explaining how old phones performed. 

I was surprised that you didn't install it with a 534A--or 334A or 295A. The 684A looks too new.

Unfortunately, 534As have usually been converted to 634As or 634BAs. Still, you can use the WR diagram with a 684, 634 or 302 base. I don't know why anyone would prefer the drop-the-capacitor  rather than the WR sidetone circuit with an anti-sidetone subset. (You don't have to change any wiring in the phone, just 2 wires in  the subset.)

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

Sargeguy

I am actually trying to sort out a 334 for that exact purpose and use the 684 for another purpose.  I have a 584D, which has no network, , so it will probably be upgraded to a 684 eventually.  I am trying to track down the wiring diagram for the 334 so I can re wire it as designed and print it out and stick it inside the door.  TCI does not seem to have it.
Greg Sargeant
Providence, RI
TCI /ATCA #4409

poplar1

The 334A, 295A and 534A are probably all wired the same. You might also look at a 333A wall set although it is rotated 180 degrees.
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

Quote from: poplar1 on December 10, 2013, 09:15:22 AM
Another reason for having two capacitors instead of one:
A capacitor that could withstand the high ringing voltages required heavy insulating paper. Because of the physical size required, it was limited to about 1 MF. By changing to two capacitors, the talk capacitor could now be 2 MF with lighter insulation.

(Ralph O. Meyer's Old Time Telephones, 2nd Ed., page 113)

I have wondered about this statement in the book.  It sounds logical, but when you examine the catalogs you'll find that even in 1908 the 21D capacitor was rated at 500V.  Yes, it was big, 1"x1"x4" or so. But it seems to have been used by itself in some subsets, I believe. For some reason later it was only used in the voice path in the subsets with two condensers (554-C and some 634As) and they used a 1μF condenser in the 534A (21BW).

poplar1

My 334A has a 21D.

While it may be true that lighter insulation for a talk-only capacitor permitted a smaller size later on (think 302); still, as you pointed out, the 554C had two capacitors.

In any case, having two capacitors allows you to have a larger value for the talk circuit and a smaller value for the ringer, particularly useful when using high impedance ringers.
"C'est pas une restauration, c'est une rénovation."--François Martin.

unbeldi

Quote from: poplar1 on December 10, 2013, 12:00:31 PM
My 334A has a 21D.

While it may be true that lighter insulation for a talk-only capacitor permitted a smaller size later on (think 302); still, as you pointed out, the 554C had two capacitors.

In any case, having two capacitors allows you to have a larger value for the talk circuit and a smaller value for the ringer, particularly useful when using high impedance ringers.
Yes, the 334A was one of those, I have found about 3 or 4 types that used the 21D. We know why the 554-C used two caps, because of its use in tip party message rate, which required the separation.

It is interesting that in the 195A in the 302, the 2μF component, while being tested at 500V, was only recommended for sustained expose to a much lower voltage, 130VDC, and I think 100VAC or so. So clearly the size argument was a consideration there.

Sargeguy

#24
Since last Thursday I have restored 13 phones, 9 are actually in sellable condition, the rest either need more extensive work such as soldering or re-painting, or replacement cords.  Of course I have only sold one phone so far (and bought another two) at the show and it looks like snow this weekend.   :(

I hadn't wired any D-1s or 302s in a few years, focusing instead on candlesticks and wood, so whatever limited wiring skills I did had atrophied.  Even if I don't sell any, I have at least cleared a backlog of unfinished projects and developed a "shtick" for demonstrating them for customers. 

Members of this forum have been invaluable as usual, especially poplar1, unibeldi, Phonesrfun and Kenton K, among others, thanks for all the help.  Hopefully I can get some sleep this weekend!  
Greg Sargeant
Providence, RI
TCI /ATCA #4409

Sargeguy

The 51-AL sold for $475 before I could swap out the 684A for the 334
Greg Sargeant
Providence, RI
TCI /ATCA #4409