Basic Testing of Old Timey Western Electric subsets (295, 334, etc.)

[Sargeguy]

*** WORK IN PROGRESS_CORRECTIONS ADDITIONS APPRECIATED***

I'm starting this post for myself more than anything because I am generally useless when it comes to wiring but I have learned a few things in the last week or so that I will most likely forget shortly.  This topic was started to consolidate a lot of the great information I got from our members.

So you purchase a subset off eBay, say a Western Electric 295A in walnut with patent dates stamped in the side and hex nuts on the nickel bells.  The set is in fantastic shape-only a moderate coat of white paint specks on the outside and no hornets' nest on the inside.  It looks like a keeper, but when you hook it up it's a dud!  What do you do next?

Step 1: Purchase a Multimeter

I use a Craftsman Digital MultiMeter Model No. 82140  that I purchased at Sears. It costs $25.  According to my electrician friend, it's "fine" for my purposes. There is another version, the 82141 which has color coded functions and doesn't include the voltage tester that you won't need, it's $20

Once you have bought your multi-meter watch this video that explains the basic functions:

How to use a Multimeter - tutorial - KK4WW

Or read the manual:

http://download.sears.com/own/03482146e.pdf

Step 2:  Hook up your subset to a known good line and see what happens.  

Make sure you have it wired so that it works.  Often times old 295A subsets have one of the ringer wires on G when it should be on L1.  The 1906 wiring diagram on the door will show it this way but you'll need a more current schematic, like the 1909 version.

Does it fail to ring?  
Do you get a busy signal when you call in or pick up another extension?  
Do you get nothing at all?

If you answered yes to either of these questions, proceed to the next step

Step 3: Test your coil

Your coil is the thing with the two wood blocks on each end and a cylinder connecting them.  It should have four wires coming from it labelled 1,2,3,and 4 respectively.  Most terminals are labelled to indicate the model number.  If not you can usually determine which coil you have once you measure the Ohms as described below.

Set your Multimeter to 200 on the Ohms part of the dial, then test the resistance between the terminals as follows:

No. 13 coil

1.4 Ohms between P and P
17 Ohms between S and S

No. 20 coil

16 Ohms between 1 and 2
27 Ohms between 3 and 4

No 46 coil

14 ohms between 1 and 2
9 ohms  between 3 and 4

101A coil

22 ohms between L1 and R
19 ohms GN and C
75 ohms between GN-R

Step 4:  Test your condenser/capacitor

The condenser/capacitor is that rectangular black or metallic block with 2 or 4 wires coming from it.


Step 5:  Test your ringer

Previously I used a Western Electric TYPE 5 magneto box with two leads terminated in alligator clamps to test ringers.  That is still the most fun way to do it, but sometimes the clapper could be seized by corrosion or the bias spring was too tight (or a combination of the two) and it would not ring.  There is a more clinical method of testing a ringer.

Set your Multimeter to 200 in the Ohms part of the dial and connect the black lead to the black wire and the red lead to the wire that used to be red.  You should receive a value close to the sum of the two numbers printed on the ringer coils.  For a 1000 Ohm ringer (500 and 500) you would expect to receive a value close to 1000.

Step 6: Test your wires

The Multimeter can also test your wires to make sure that they are capable of conducting electrical current.  FRom the manual:

CONTINUITY CHECK
WARNING: To avoid electric shock, never measure continuity on
circuits or wires that have voltage on them.
1. Set the function switch to the position.
2. Insert the black lead banana plug into the
negative (COM) jack
Insert the red test lead banana plug into the
positive ($) jack.
3. Touch the test probe tips to the circuit or wire
you wish to check.
4. If the resistance is less than approximately 30$,
the audible signal will sound. If the circuit is
open, the display will indicate "1".

This can also be helpful when figuring out which dingy gray wires in the wiring harness lead back to which circuits in the coil or capacitor, or for figuring out which conductor is which in old faded cords.

[Sargeguy]

Other Tools that May Come in Handy:

A two line spade to modular cord with alligator clamps attached to the spades.  This saves you the trouble of screwing and unscrewing the line to the terminals on subsets of phones that do not have lines attached, or troubleshooting the line cord

A 2MFD 100VDC capacitor (actually should be 2MFD 250VDC) with alligator clamps attached to each end.  Convenient when bypassing a condenser to see if it is the problem.

A set of 4 test leads in Red, Green, Black and Yellow.  This is really handy when you need to test the functionality of a subset connected to a desk stand or desk set.  Connect one end to the spades on the subset cord and the other to the terminals.  Save a lot of screwing and unscrewing or dragging around the subset with the phone attached.  Also enables you to troubleshoot the subset cord by bypassing it.

A known "good" phone.  Got a manual D-1 missing it's base plate with crappy paint and a chewed up F-1?  Perfect! provided it works

[Greg G.]

Awesome!  I was asking how to test subsets in a separate thread a while back.  I'll bookmark this and come back to it.

[Phonesrfun]

Greg (Sargent):

Your resistance measurements of the induction coils all match exactly to the values Ralph Meyers uses in his book "Old Time Telephones...."

You left the number 13 coil blank, probably because you didn't have one to measure.  On page 100 of his book, in table 15.1, he lists the number 13 coil.

P-P would measure 1.4 Ohms, and S-S would measure 17 Ohms.

[Sargeguy]

I am in the process of looking for Ralph's book, among other things.

[Greg G.]

Step 1: Purchase a Multimeter

I use a Craftsman Digital MultiMeter Model No. 82140  that I purchased at Sears. It costs $25.  According to my electrician friend, it's "fine" for my purposes. There is another version, the 82141 which has color coded functions and doesn't include the voltage tester that you won't need, it's $20

Once you have bought your multi-meter watch this video that explains the basic functions:

How to use a Multimeter - tutorial - KK4WW

Or read the manual:

http://download.sears.com/own/03482146e.pdf

Will one of these suffice?  If not, I'll ask Anita for the Craftsman meter for Christmas.

[Sargeguy]

I think so.

[Phonesrfun]

I use a digital multimeter a lot, but frankly some things are better served with an analog multimeter (the kind with a pointer-type needle).

My digital meter has a capacitor checking setting that allows me to actually measure capacitors.  However, when I want to do a quick check of a capacitor, I still use the analog meter using resistance (ohms).  Note that by using an ohm meter to check a capacitor, the ohm meter is not used to tell you the value of the cap.  It only shows you the results of putting a small charge on the capacitor from the internal battery of the ohm meter.  It shows visually the charging and discharging of the cap.  That is all it shows.

When using an analog ohmmeter to check a capacitor, you want to put the meter in the ohms position and set it on a low ohms setting.  Connect the test leads to the capacitor and the needle should temporarily show conductivity as the cap is charging up, and then settle down to no conductivity (infinite resistance) as the cap becomes fully charged.  Reverse the test leads on the cap and the needle will once again jump as the capacitor discharges and then re-charges with the opposite polarity from the meter.  Once again as the cap becomes fully charged from the meter battery, the meter will go down to infinite resistance.  The larger the micro Farad reading of the cap, the larger and slower the jump of the needle.  

The problem with a digital ohm meter to view the charging and discharging of a capacitor is the fact that it samples the readings, and the values of the samples go flashing by as a stream of meaningless numbers.  The needle on an analog meter jumps and you can actually watch it jump.  Granted, it happens quickly and doesn't give a useable reading, but one gets a feel for it after a while.  A digital meter with a capacitor checker would be optimum if you want to pay out for that feature.

The older caps in older phones, say, pre 1930's are notorious for breaking down and not functioning very well.  Once they break down, they tend to act more like a resistor, or worse as a dead short.  Capacitors made after the 2nd World War were much better, especially many in telephony, since the world was able to benefit by work the Gemans had perfected in making metal film capacitors that were much smaller and more reliable than other caps out ther before that time.