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1957 Stromberg Carlson Hands Free Phone

Started by ....., July 24, 2017, 08:25:44 PM

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Alex G. Bell

Quote from: paul-f on July 28, 2017, 03:52:44 PM
You're welcome, Doug.

I see I haven't updated that page since 2002.  As I recall, I had a digital camera that was tethered to my computer, as most of the electronics were on an ISA card inside the computer. Those 320px × 240px photos were the maximum resolution!  How things have changed. I should update the page as time permits. I'll also check the paper files for more info.
That's surprising!  My first digital camera, purchased probably mid or 3Q 2003, was a stand-alone "Argus" brand device with fixed focus lens and 1600x1200 resolution.  But it had a "meniscus" lens for close-ups and did a very decent job of it.

It contained 16MB but accepted SD cards up to 2GB IIRC.  The first SD card I bought for it was 256KB.  When the  output was connected and set for NTSC video it also functioned as a live color video camera.

This camera cost $40 on clearance at Office Max, so it was already obsolete by mid/3Q 2003.

TelePlay

Quote from: Duffy on July 27, 2017, 08:18:04 PM
Thanks Paul for the picture and the link to your site. That information will help me out a lot with my restore.

Getting back to the missing microphone, have you found one at a reasonable price and if so do you mind saying where? I saw one on eBay where the seller wanted $450 for it. I think it shipped from Colorado, or one of those states. There seem to be quite a few on eBay right now ranging in price from under $50 up to $150.


paul-f

Quote from: Alex G. Bell on July 28, 2017, 04:17:19 PM
That's surprising!  My first digital camera, purchased probably mid or 3Q 2003, was a stand-alone "Argus" brand device ...

Not so surprising with the rest of the story. The computer with attached/integrated Intel brand camera was purchased at an industrial bankruptcy sale in the mid-1990s, so was old then. I bought my first "real" digital camera in 2003.

I've added a new snapshot of a nicer microphone from my collection on the web page and below.
Visit: paul-f.com         WE  500  Design_Line

.

Alex G. Bell

Quote from: paul-f on July 28, 2017, 06:08:01 PM
Not so surprising with the rest of the story. The computer with attached/integrated Intel brand camera was purchased at an industrial bankruptcy sale in the mid-1990s, so was old then. I bought my first "real" digital camera in 2003.

I've added a new snapshot of a nicer microphone from my collection on the web page and below.
What is its resistance?  Does it attract a compass needle?

Do you have the rest of the speakerphone? 

paul-f

Quote from: Alex G. Bell on July 28, 2017, 06:15:02 PM
What is its resistance? Measures infinite.

Does it attract a compass needle?  Yes.

Do you have the rest of the speakerphone?  Yes. Needs new cords and hasn't made it to the top of the project list.
Visit: paul-f.com         WE  500  Design_Line

.

Alex G. Bell

What is its resistance?
Quote from: paul-f on July 28, 2017, 07:38:15 PM
Measures infinite.
Does it attract a compass needle? 
QuoteYes.
Do you have the rest of the speakerphone? 
QuoteYes. Needs new cords and hasn't made it to the top of the project list.
If it attracts a compass needle it's probably dynamic and should not have infinite resistance.  My commercial Shure M510 measures 1000 ohms, which is high but reasonable for a dynamic mike.  Let's hope your connecting cord is open otherwise the element might be.

Have you ever had the main unit open?  If so, does it contain tubes or transistors?

Do you have full docs including schematics?

zenithchromacolor

#21
The Shure Controlled Reluctance models are expensive because the element is highly desired for use with amplified harmonica playing, often the elements are transplanted into "bullet" housings that are easier to hold against the harmonica. As mentioned, the same housing was used for crystal elements, which sell for much lower prices, such as the Shure 710. Note that the crystal elements tend to go bad with age, especially if they are exposed to a moist environment.

For example:

http://www.ebay.com/itm/172746775997

=============

EDIT:  Above listing for a 710A Crystal microphone sold on eBay for $15.00 with free shipping on July 24th, 2017.


.....

#22
I have had a chance to do some work on my phone. It's late so I'll post more before and after pictures later.

.....

#23
More pictures, Can anyone date this phone with the numbers shown? I also found the schematic tucked away inside the phone. Can you see it?
I need to replace the handset cord as this one is cracking. I used some heat shrinking tube to hold it together until I get another cord. There is one on eBay, but it's a little pricey. I also need the wall cord. 

Quote from: TelePlay on July 28, 2017, 04:35:13 PM
Getting back to the missing microphone, have you found one at a reasonable price and if so do you mind saying where? I saw one on eBay where the seller wanted $450 for it. I think it shipped from Colorado, or one of those states. There seem to be quite a few on eBay right now ranging in price from under $50 up to $150.

John, I think I may have found one with the correct end for a very reasonable price.

paul-f

Beautiful, Doug!

You have answered a lot of questions regarding what's inside.

With your permission, I'll add the schematic to the TCI Library.

Visit: paul-f.com         WE  500  Design_Line

.

.....

Quote from: paul-f on July 29, 2017, 11:04:56 AM
Beautiful, Doug!

You have answered a lot of questions regarding what's inside.

With your permission, I'll add the schematic to the TCI Library.

Sure, go ahead Paul. If you want larger resolution pictures I have 4000 X 6000 copies of each one.

Doug

unbeldi

#26
Quote from: paul-f on July 28, 2017, 07:38:15 PM
What is its resistance? Measures infinite.


The circuit diagram indicates that the 1583 uses a piezoelectric microphone, so its resistance should indeed be essentially infinite.

It should be easy to find a microphone at reasonable cost to at least get this unit working as intended.  Look for a Shure 710A, CA80, or so.

Perhaps: http://www.ebay.com/itm/382179697587
or:   http://www.ebay.com/itm/282586027406
or:   http://www.ebay.com/itm/182654863218
...

unbeldi

#27
The set contains several date markings in forms 7 10, 71x.

I believe at least until the mid-1960s (~1964 last observance), SC used the code format  ww-yy, were ww is the week number of year, and yy is the year.

This clearly deviates from that, I think the year is now simply a single digit, perhaps omitting the decade digit, and the format appears as y-ww.
So perhaps:
710 = March 1967 1957
715 = April 1967 1957
                                 PERHAPS.


The 210558 transmission unit, or network, is the standard type that was used in the 1543.

.....

Quote from: unbeldi on July 29, 2017, 12:33:40 PM
It should be easy to find a microphone at reasonable cost to at least get this unit working as intended.  Look for a Shure 710A, CA80, or so.

Perhaps: http://www.ebay.com/itm/382179697587
or:   http://www.ebay.com/itm/282586027406
or:   http://www.ebay.com/itm/182654863218
...

or maybe even this one: http://www.ebay.ca/itm/322610016853?ul_noapp=true   :)

Alex G. Bell

#29
The WE 1A and AE 88 Speakerphones also use hearing aid tubes (but 2 instead of 3) and (2) 3V4 miniature tubes. The circuit is probably quite similar.  However the 1A speakerphone used a modified U-style receiver unit as a dynamic mike.

The WE and AE use a mike input transformer with a low impedance dynamic mike instead of a crystal (piezo) mike.  The S-C uses a 3rd hearing aid tube as a mike preamp instead of an input transformer.  No doubt this was less costly and only possible because the amplifier was integrated with the phone and therefore nearby.  With the WE and AE the mike might be some distance from the control unit containing the amplifier.

Perhaps the original Shure mike was ceramic rather than "crystal".  Both are essentially piezo electric but ceramic has much lower output and I believe is much more stable over the long term.  That might explain the need for a 3rd hearing aid preamp tube.  I'd think that a crystal mike might not need a preamp tube but a ceramic one more likely would.