I have two D1 phones and two 295A subsets. Both phones work on subset #1, neither works on subset #2.
Subset #2 has a slightly different schematic on the inside of the lid, but the terminals are all the same. Both subsets have L1, L1, 2, 4, C and G. The only difference between the two is that subset #1 has (2) L2 terminal, while subset #2 only has one L2 terminal.
When I connect a working D1 phone to subset #2 I can faintly hear a dial tone. When I dial the dial tone does not break. It's very faint. When I use another phone in the house to dial my number when this working phone is attached to subset #2, I get a busy signal.
I've attached a diagram showing how I have subset #2 wired. I do not attach anything to the ground terminal. There are no wires spades touching an adjacent terminal. I have switched the red and green line cords to change polarity. So far, I've not been able to find anything different between the wiring of the two subset. I have also checked with my meter the ohms for all components in both subsets and the components measure "good". When I connect my analog meter to the capacitor the needle jumps quickly to the right then holds steady for a bit before it starts to wobble a little and might even jump to the left about half way before return all the way to the right. I don't know if this is significant of anything or not.
Larry
Te diagram you supplied is correctly wired, so I would check to see if the condenser (capacitor) which connects to L2 and C and in series with the ringer coil is shorted. That is the nature of what you described. If so, the ringer, which has a low resistance is effectively connected directly across the line, busying it out. If it is shorted, you could find a smaller 2mF cap to put in the circuit while leaving the bigger old capacitor in place.
What voltage would that 2mF capacitor be?
I suspected the capacitor was faulty. When I disconnect one lead from the capacitor I don't get a busy signal when calling my number.
Larry
250 volt
A 295A subset has a low impedance ringer, so with a 2 µF capacitor you're going to load your telephone line quite heavily. If you have additional telephones on the line, this may result in ring trip. The original capacitor in the subset had 1 µF.
The impedance of a capacitor decreases with increasing size at a given frequency, so it would be better to stick with the original value.
The value used in these subsets, that had the capacitor function as both the ringing capacitor as well as the DC-blocking capacitor in the audio circuit, is a compromise. In the audio circuit one would want the capacitor as large as possible. Western Electric used 2 µF units for that; Automatic Electric even used 4 µF and 5 µF in the AE 34 and 40. The ideal size of capacitor just for ringing would be 0.5 µF, so 1 µF indeed seems like a good compromise that doesn't attenuate the audio too much, while also not loading the line too heavily.
Note that the unit is microfarad (µF, in old literature M.F.), not millifarad (mF).
PS: Well, I stand corrected by the 1908 catalog which still specifies a 21-D condenser, which is a 2 µF unit (huge). Later, they used a 21-AA of 1 µF. But, based on the science of electronics, I would not use 2 µF.
Quote from: Phonesrfun on August 27, 2015, 03:56:46 PM
250 volt
Where do you buy that capacitor? It's not marked 2mf.
It is marked 2.2k which is 2.2 micro Farad. I just tested it on my digital VOM and it tests at 2.253 micro Farad. I bought a few of these a few years ago at an electronics surplus store. I mentioned in a private message that I would send you one no charge. As unbeldi said, a lesser capacity one would probably load the line down even less than a 2, but all I have are 2's. 2 is the original value, so at least it would be electrically original. The older ringers were much lower in resistance as compared with the later ringers. So, if you want a 2 microfarad, PM me with your address.
Larry:
I just got your PM
Quote from: Larry on August 27, 2015, 06:00:29 PM
Quote from: Phonesrfun on August 27, 2015, 03:56:46 PM
250 volt
Where do you buy that capacitor? It's not marked 2mf.
Unfortunately, there is no uniform marking of capacitors. The systems in use today depend on the size and the type of the capacitor, and sometimes on the manufacturer.
Larger units with enough room for printing often have the size written out in full. Others use 2 or 3 digits which represent a base value and an exponent for decimal multiples of pF, and sometimes nF.
The one shown has only the numerical value and no unit, and apparently the implied unit is µF (which can also be inferred from the size). So its nominal value is 2.2 µF. The capital K designates the manufacturing tolerance, which is 10%. A capital J would be 5%. So in practice, this unit could be anywhere in the range of ca. 2.0 to 2.4 µF.
Thanks for the explanation. It's been a long time since I worked with capacitors and resistors. The markings on the capacitor made it look more like a resistor.
Many years ago I "tinkered" with old radios from the 20s - 40s. On occasion I could rejuvenate a capacitor by overcharging it for a bit. I guess that doesn't work on these condensers from the earlier days.
Quote from: Larry on August 28, 2015, 12:27:57 PM
Thanks for the explanation. It's been a long time since I worked with capacitors and resistors. The markings on the capacitor made it look more like a resistor.
Many years ago I "tinkered" with old radios from the 20s - 40s. On occasion I could rejuvenate a capacitor by overcharging it for a bit. I guess that doesn't work on these condensers from the earlier days.
That doesn't work with old capacitors like these usually. Perhaps a very high current from a car battery can burn out a short, but this is not reliable. Only capacitors made from metallized films can be healed reliably. I think those didn't become available in the US until after WWII, when the equipment was removed from Germany and replicated. Western Electric was largely involved with that and ... presto... they were able to make capacitors that were a fraction of the previous size, for example in the 500 set.
In the 1910s or so, Western Electric repaired
some condensers by inserting into the roll of foil and insulator (paper usually) from the end a new pickup electrode. This yielded a capacitor that was somewhat smaller in value than the nominal capacitance, but still deemed satisfactory. This is explained in some Bell System document. I think it may have been a specification explaining some capacitors with smaller sizes. But by the end of WWI they realized that the old capacitors where too large anyways from an electrical stand point, and the 1 µF condenser became the standard for single condenser substations.
Perhaps you could remove the capacitors from both phones, exchange them, reconnect each one in the other phone, and test. If the fault follows the capacitor, ...
Bill
Quote from: Phonesrfun on August 27, 2015, 03:56:46 PM
250 volt
Ok. Capacitor received and installed. Phone now dials out and receives incoming, but the bells didn't ring. The coils for the ringer are 500 ohms each and I got 960 on my meter when I checked across them. I double checked my wiring and that's correct. Then it hit me. BIAS SPRING.
So, adjusted the bias spring and this old time D1 102 with scratchy E1 bullet is working again!! I found a replacement E1 with a 626 transmitter so I'll replace the E1 in a few days.
Thanks to everyone for helping me along. Learned a lot and had fun, too.
Larry
Wow, the post office did a fast turn-around on that one!
i was really surprised to get it today !!
LW
Not to move too far off topic, but I just read an article in today's paper that said that the post office is reporting that late mail is up by 50% this year as a result of the closures of distribution centers.
As it is, from my town in Walla Walla, WA, even though we have a post office, our outgoing mail is postmarked from Spokane about 150 miles away.
PS:
Congratulations on getting it to work and thinking about the bias spring. Good work.
Mailed from Walla Walla Washington on Saturday arrived here in Myrtle Beach, SC today. That's the fastest service I've ever received from the West Coast. It usually takes a week.
LW