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HA-1 vs. HC-3 receiver element

Started by Jack Aman, March 07, 2015, 06:55:40 PM

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Jack Aman

Hey guys...what is the difference between the HA-1 and the HC-3?  Are they interchangeable?

unbeldi

#1
The HC3 receiver is slightly smaller than an HA1.  The HC receivers had increased gain over the HA elements.

These receivers were primarily used in headsets, including the Nos. 52 and  53 operator sets.

Since they had better efficiency, they were sometimes installed into F1 handsets for stations on very long loops from the central office.  For this purpose,  Western Electric made a brass adapter ring so that an HC3 could be used in an F1 handset.

In this photo I captured a receiver that was originally an HC3, but is converted to an HC5 (see ink crossout and stamp) with the brass adapter ring.  There are two HC5s, front view and rear view.



Ok, the HC5 is a variation of the HC3 with a slightly modified connector plate so that it matches the contacts of HA1 element.  The adapter ring is part of the HC5 package.  The electric characteristics of the HC3 and HC5 are identical.  300 Ω impedance at 1000 Hz.


There was also an HC4 with twice the impedance of the HC3.


PS: I almost forgot, I found an HC5 in a 202 telephone not very long ago:  HERE





unbeldi

#2
I found an eBay auction with pictures of an HC3.

Here is what that terminal plate looks like:

Jack Aman

Could one of these be made to work in an E-1 handset?  One of my daily drivers is a D1 with an E1 handset that was overhauled for me.  The E-1 has been converted with an electronic transmitter, and some type of receiver capsule in place of the original tinny sounding diaphragm type device.  It is not strictly "original" any more of course and I suppose purists would disapprove, but it looks terrific and functions beautifully and I use it every day.  The receiver cap is fused on tighter than June Cleaver's hairdo as these are prone to do and I can't peek and see what has been put in there.  I now have another E1 and would like to undertake the conversion myself.  What will fit in there?

unbeldi

#4
I have not pondered that.

Here is what the receiver in an E1 handset looks like after removing the diaphragm.


An HA1 is probably too large, but perhaps an HC3 or an LB1 could be fitted. I think the LB1 may have a lower profile than the HC3.  It was used in the later versions of the No. 52 head set.
But it would probably still require a lathe to turn out the receiver assembly.

....
PS:   Ok, even an LB1 is too large in diameter to fit inside the receiver assembly. It's about 3 millimeters smaller in diameter than the outside.  Conceivably there might be enough material so the assembly cylinder could be turned out. But the height of the LB1 isn't much better turns out.

I am sure there more modern alternatives from some audio headset that would make a better fit.

Jack Aman

Thanks as always for the exellent info.

unbeldi

What kind of electronic transmitter was used in your converted handset?   Is it a little printed circuit board with a chip on it?

Jack Aman

It is a fiberglass disc appropriately sized to fit in the transmitter housing of the handset.  Stuck on to it with a dab of silicone is a little round microphone element about 1 cm in size.  On the backside are a couple of little electronic widgets (sorry I can't be more specific)  little cylinders with color codes on them.  A pair of wires red and white with spade ends connect to the lugs within the handset.  Clever design...my callers indicate my outgoing transmission is perfectly clear...much better than people get used to accepting as normal in the cellphone era.

Jack Aman

It seems like I read here (or somewhere) that a Trimline receiver capsule could be used to retrofit an E1 handset.  Does anyone here recall that thread?  Or has anyone done it?

rdelius

Here is an example of a modified one.The capsule is similar to an LB1 and made by Audiosears.The old magnet was removed. the screws shortened and the inside turned on a lathe for more room to fit the modern capsule.

Jack Aman

Nice clean modification.  Is that element comparable to a Trimline capsule?   Thanks.

rdelius

Same diameter but only 1/2 inch thick

unbeldi

Indeed it looks like this one has the same diameter as the LB1, judging by the amount of metal wall remaining after machining. It looks about what I would have expected to remain.