Regarding AE40 Receiver pop

[Partyline4]

I realized a while back that the reason that many older telephones such as the AE40 produce a loud POP! when the handset is lifted is because there is no varistor.

The question in mind is would that continuous POP! cause any damage to the receiver?

If it has lasted this long making that POP! thousands of times, does the loud POP! really damage the element?



What are your thoughts?

[unbeldi]

Until the 500-set introduced in 1950, no Western Electric telephone ever had a varistor installed from the factory.  Varistors didn't exist until the very late 1920s after the copper-oxide rectifier effect had been discovered in 1927.
After that it was only used for certain applications.

The 202 and 300-series got along very well without them, having carefully designed hook switches and off-normal dial contacts that provided proper sequencing in establishing a circuit and removing the receiver at appropriate times.

Other manufacturers were not as diligent.  But still I am not sure that an AE40 should be so annoying, at least I don't recall observing that on mine. The hooks switch in the AE-40 must be properly sequenced so that one set of contacts makes last (or breaks first).

[Partyline4]

Does anyone have a link to the adjustment specs for the AE40 H.S.?

It seems to be normal.


My Cousin down the road has an ivory AE40 that does the same thing.

You hear a loud pop when it goes off hook.

[unbeldi]

Ok, I took a look at the circuit diagram of the AE 40 and have to concede that this can hardly be avoided.  This may not be apparent from the wiring diagrams as they don't make it exactly easy to understand the actual operation of the set.

I posted a forum topic in the wiring diagram section with a true circuit diagram, and here it is:



The topic is here:  http://www.classicrotaryphones.com/forum/index.php?topic=13908.0

I will expand the post there eventually with a circuit description.

But briefly, we can see that the sequencing of the hookswitch contacts, HS1 and HS2, only assures that the ringer is disconnected from the line by HS2 before the audio circuit is connected by HS1.  This switching action also completes the circuit of a high-frequency filter (R1, C1) to minimize radio interference while dialing with an RC filter across the hookswitch and the dial pulse switch (DP).

The circuit does not exclude the receiver from the circuit during the on- to off-hook state.  This makes the receiver susceptible to some noise. There is some damping of the pop provided by the filter (R1,C1) but this likely only prevents arcing between the contacts, and some pop seems unavoidable.

During dialing the off-normal switch ON2 places a shunt across the receiver to kill off any pops.

So, there is really nothing to adjust here other than to make sure that HS1 closes only after HS2 has already transitioned.

The only modern aid that could be applied is to use a different dial with more ON contacts—AE did make such dials to be compatible with Western Electric—or to install a varistor.  The varistor could be installed between terminals R and C inside the telephone set.

Hope this clears that up.

[Partyline4]

Thank you so much Unbeldi!

What a mammoth of information!


I discovered that when the switch hook moves rapidly, there is no pop.

It seems like the sluggishness determines the severity of the pop when going off hook.


Very interesting.

[KaiserFrazer67]

Glad I found this thread; I hope you don't mind my re-opening it.

I am having the same hookswitch pop problems with a newly-acquired AE 50 wall phone that I'm restoring.  Close observation of the hookswitch while opening and closing it shows me that HS1 is breaking first and making last as it is supposed to.  I'm glad I'm not the only one with this problem, so from what I can gather from this post, hookswitch pop on an AE 40/50 seems to be, to a certain extent, SOP.

Unbeldi, you mention putting a varistor in between the R and C terminals to dampen some of the pop; what type/size of varistor do you recommend, and where can I get one?   I don't have as much understanding of telephone circuitry as I'd like--not yet, anyway.  I have some very basic electronics training from tech school (late 1980's-early 1990's), but we covered rheostats and potentiometers, not varistors (I had to just look up what one is, in fact).  It's like trying to clean the cobwebs off of information I literally haven't used in almost 30 years!  Thank goodness I can still read a schematic (for the most part...  ).

Thanks much,

-Tom from Oakfield, Wisconsin

[twocvbloke]

The GPO's solution to the receiver pop was a Rectifier No. 205A which was two back-to-back diodes wired in parallel with the receiver (usually inside the phone at the receiver terminals), this was to reduce the possibility of acoustic shock when pressing the hookswitch with the receiver still at the users ear...

[unbeldi]

Glad I found this thread; I hope you don't mind my re-opening it.

I am having the same hookswitch pop problems with a newly-acquired AE 50 wall phone that I'm restoring.  Close observation of the hookswitch while opening and closing it shows me that HS1 is breaking first and making last as it is supposed to.  I'm glad I'm not the only one with this problem, so from what I can gather from this post, hookswitch pop on an AE 40/50 seems to be, to a certain extent, SOP.

Unbeldi, you mention putting a varistor in between the R and C terminals to dampen some of the pop; what type/size of varistor do you recommend, and where can I get one?   I don't have as much understanding of telephone circuitry as I'd like--not yet, anyway.  I have some very basic electronics training from tech school (late 1980's-early 1990's), but we covered rheostats and potentiometers, not varistors (I had to just look up what one is, in fact).  It's like trying to clean the cobwebs off of information I literally haven't used in almost 30 years!  Thank goodness I can still read a schematic (for the most part...  ).

Thanks much,

-Tom from Oakfield, Wisconsin

As already stated, you can indeed use two anti-parallel diodes.  Or if you have some junk U1 receiver capsules from 500-type sets, you can take the varistor off the back.

If using modern diodes, two of the 1N400x series will do.  They range from 50 volts for 1N4001 to 1000 V for 1N4007, so any will work.  They are dirt cheap, pennies a piece, and typically I have bought the whole set with 5 or 10 each for a dollar or two from Chinese eBay vendors.  Many of those even provide free shipping, which takes two or three weeks.

[KaiserFrazer67]

...Or if you have some junk U1 receiver capsules from 500-type sets, you can take the varistor off the back.

I take it that's the round silver thing that says "44A" on it?  So that's what that does...!    Just so happens I have one out of an extra 554.
Thanks very much for the tips, Unbeldi.  I will try that!

[poplar1]

Phoneco (phonecoinc.com) in Galesville, Wisconsin has lots of extra varistors from all the hot-wired repro candlestick phones. Last time I checked they were asking 25 cents each.