Author Topic: WE J/K-500, 5-52  (Read 4670 times)

Offline McHeath

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Re: WE J/K-500, 5-52
« Reply #15 on: May 09, 2010, 02:08:29 AM »
Yeah that's what it was!  Funny how some things stick in the mind and you can't forget them no matter what, while other things simply won't stick no matter how hard you want them to.  I cannot get the resistor reading colors and tolerance codes to stick, but I can recall useless factoids about long dead Byzantine emperors that I learned in my teens.  The mind is funny that way.

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #16 on: May 09, 2010, 12:39:26 PM »

McHeath;
Remember...
 
Black is-0
Brown is-1

Then they go in rainbow order...
Red-2
Orange-3
Yellow-4
Green-5
Blue-6
Violet-7
Gray-8
White-9

Tolerance
No 4th color band-20%
Silver 4th Color Band-10%
Gold 4th color band-5%

http://tinyurl.com/22ww4y7

D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #17 on: May 09, 2010, 12:41:51 PM »
Briny;
Where the heck is Claude from Cleveland, I want my copper clapper returned.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #18 on: May 09, 2010, 06:15:56 PM »
By definition, the 500 J/K did NOT have an equalizer. 

It was made purely for long loops where limiting both the current and the sidetone were not necessary.  that is why there is a flat terminal board in place of the equalizer.  It is not a matter of having a burned out component in the equalizer, because there is none.

Naturally, when hooked to a normal loop, it will have too much volume and objectionable sidetone if not limited by a resistor.





Bill;
Check this pdf, it does say the J/K has an equalizer, or is J or k different from J/k.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline Phonesrfun

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Re: WE J/K-500, 5-52
« Reply #19 on: May 09, 2010, 09:01:47 PM »
Bill;
Check this pdf, it does say the J/K has an equalizer, or is J or k different from J/k.
D/P

Notice that the diagram is for both the A/B and the J/K, and it says that the J/K version has the terminal strip.  While it doesn't come out and say that the terminal strip is in place of the equalizer on the J/K, that is what is meant.  It is probably covered in detail in a BSP someplace.

-Bill G

Offline Jim S.

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Re: WE J/K-500, 5-52
« Reply #20 on: May 09, 2010, 09:21:12 PM »

McHeath;
Remember...
 
Black is-0
Brown is-1

Then they go in rainbow order...
Red-2
Orange-3
Yellow-4
Green-5
Blue-6
Violet-7
Gray-8
White-9

Tolerance
No 4th color band-20%
Silver 4th Color Band-10%
Gold 4th color band-5%

http://tinyurl.com/22ww4y7

D/P
Remember:
Bad Boys Rape Our Young Girls But Violet Gives Willing, Sometimes
for Gold, sometimes for Silver, and sometimes for Nothing.
Bad _Black
Boys_Brown
Rape _red
Our _orange
Young_Yellow
Girls _Green
But _Blue
Violet_ Violet
Gives _Gray
Willing_ White

Tolerance

Gold 5%
Silver 10%
Nothing 20%


Jim
You live, You learn,
You die, you forget it all.

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #21 on: May 09, 2010, 10:11:21 PM »
Funny how those sayings can stick for life. When I was 10 i took some music lessons, and that taught us FACE, EGBDF, Every Good Boy Does Fine.

D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #22 on: May 09, 2010, 10:23:53 PM »
Bill;
Check this pdf, it does say the J/K has an equalizer, or is J or k different from J/k.
D/P

Notice that the diagram is for both the A/B and the J/K, and it says that the J/K version has the terminal strip.  While it doesn't come out and say that the terminal strip is in place of the equalizer on the J/K, that is what is meant.  It is probably covered in detail in a BSP someplace.



Bill;
 If the Equalizer was indeed replaced by the terminal block, wouldn't the schematic also note what replaced the need for the Eq, and note as such on the schematic. I still don't understand why the Eq all of a sudden was no longer needed.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline Phonesrfun

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Re: WE J/K-500, 5-52
« Reply #23 on: May 09, 2010, 11:14:18 PM »
Bill;
If the Equalizer was indeed replaced by the terminal block, wouldn't the schematic also note what replaced the need for the Eq, and note as such on the schematic. I still don't understand why the Eq all of a sudden was no longer needed.
D/P

Dan:

It was not a matter of the equalizer no longer being needed, per se.

BTW, Faul F's site has the BSP references for the 500 J/K model and also states that the J/K was the equivalent of the A/B, but without the equalizer.

Here is the story on that as I understand it.

The equalizer first of all was costlier than their earlier pro forma analysis had come up with.  This is even stated in the 1953 Bell System Technical Journal article that announced the 425B network, where they combined the equalization circuit in with the 425 network and made it all one unit.  In the reading of the 1949 article where they are discussing the properties of the equalizer, they state that on long loops, the effect of the equalizer is almost negligible, but not quite.  In other words, the equalizer which had a sole purpose of reducing the current and the sidetone on short loops was supposed to not have any effect on long loops, but it still did have some small effect on those long loops, which would make it so that even on long loops there was some attenuation of the voice current.  

It appears that the whole reason for having the 500 J/K without the equalizer was only for the long loop situations where the full advantage of the T1 and U1 receiver could be realized with zero attenuation.  Those long loops with the older 302's and older needed the 307 which was set up for local battery talking and common battery signaling.  The 500 J/K was, I believe a totally common battery solution that did away with the need for the local battery on long loops previously required by the 307.  So, not only was the equalizer a costly item to have on the longer loops and was not even needed, it still had some objectionable attenuation, thus the need for one without an equalizer altogether, and thus the 500 J/K.

Apparently, the 1953 425B network that used varistors in the equalization circuit did have zero, or at least closer to zero attenuation on the longer loops, and that did away with the need for the J/K series altogether in the later model.

If anyone else (Paul?) wants to chime in on this thread with their understanding, that would be great.

-Bill G

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #24 on: May 10, 2010, 12:11:26 AM »
I think I understand now what you are saying. The equalizer was not needed to the point that it could be left out with negligible notice to performance, then in 53 they added what was required to solve a little problem but not a major problem thought previously to be more of a problem then it really was.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline Phonesrfun

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Re: WE J/K-500, 5-52
« Reply #25 on: May 10, 2010, 01:13:45 AM »
Yes, with one important thing.  The equalizer was needed on short loops where the current was high enough to create a condition where the new transmitter and receiver elements (T1/U1) were too efficient and would cause objectionably loud volumes and sidetones without equalizations, and therefore needed the equalizer to knock it down to basically 302-like levels.  The 500 with the new T1/U1 elements were far superior to the 302's F1/HA1 elements on longer loops.

Remember, that on short loops, the voltage and current at the home was higher and more efficient than on longer loops where there was far more line resistance.

The whole excercise of designing the T1/U1 transmitter and receiver was to extend the range of the phone on longer loops.  On shorter loops, this was not needed, so the equalizer was placed in the phone to basically un-do the gains that were created by the new elements.

This was particularly important where a phone was in an office.  Let's say that the XYZ company that had a PBX was 5 miles away from the central office.  Calls within the office were extremely short loops.  Measured in feet or hundereds of feet.  The phone would need an equalizer to knowck down the volume for calls within the office, since the PBX provided battery right there on premises.  However, once the called dialed "9" for an outside line, they were connected to a line whose battery was 5 miles away.  The equalizer needed to compensate and allow the full volume and no attenuation during that call for things to be equal.

Now take the example of the farmhouse that is 10 miles outside of town.  It would never need attenuation, since every call is over a long loop and the equalizer would be a costly part of the phone that would never be called into service, and in fact, due to the fact that attenuation on the early equalizer could never be taken all the way out, would actually add attenuation to the call unnecessarily.   The J/K without an equalizer would be the solution there.

In the case of the farmhouse in the 302 days, there was so much loss in the line that a standard 302 would not work well, so they had the 307 with the local battery to provide the necessary power to drive the F1 transmitter.

My hat is off to the research at Bell Labs to work to tackle all this and to get us to where we are today, to the point where one phone is so versatile that it can handle a very wide range of line loop lengths and resistances and compensate accordingly.  But it was something that came about by better physics and by newer components that came about with semiconductors that could control impedances based on voltage, current, and resistance.

The 500 was an example of a lot of engineering and a balance between optimum performance and cost.  Cost would dirive the R&D to create newer and better components, and the drive to provide the best service over a wide range of electrical variables was also driving the quest for providing a standard level of service to all subscribers, so that the experience of using the phone out on the farm would be pretty much the same as the person who lived in an apartment that was right across the street from the central office.

Each mile of cable between the subscriber and the central office inserts an additional 430 ohms of resistance and 3.5db of voice loss at voice frequencies.  Some central offices had subscribers located very far away and some very close and everything in between.  The big probems with 302 and earlier phones were the subscribers located at the fringes of the central offices.

I believe the thing that drove this at the Bell System was that after the war, there were many GI's that under the GI bill bought new homes out in the suburbs, and there was a great need for a phone with greater gains, but at the same time those gains needed to be mitigated for the core subscribers still located close in.  Otherwise they would have been forever needing a model for close in and another model for the far away places, and perhaps yet another one for the in-betweens.

Until they came up with a more efficient equalizer than the one used in the early 500's, The J/K was designed for the outer parts of the fringe areas where absolutely no volume reduction could be tolerated.  The J/K model was discontinued with the 425B network.

There were still times when a subscriber was so far out that even the 425B was not efficient enough to do the job.  At that point, they put repeaters in to handle those situations to boost the signal along the way.

I live in a rural area where up in the hills there are people that are 10, 20 miles and even further out.  To this day, there are repeaters that serve those people.  They can be seen along side the road.  Some look like a stainless steel pressure cooker attached to a pole.

-Bill G

Offline Jester

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Re: WE J/K-500, 5-52
« Reply #26 on: May 10, 2010, 06:29:54 PM »
McHeath,
Thank you for the picture--it confirmed what I was thinking, but better safe than sorry.

D/P,
Thank you for the interpretation of the color bands!  Since I don't have those commited to memory, I try to keep a cheat sheet around.  Mind you, I always lose track of where I last laid it. ;D

Bill,
Since you mentioned that questions are good on another thread, I have a couple for this one.

1.  You continuously mention "rural service" in reference to the J/K/T phones.  Is there any knowledge or documentation on how far from central(minumum) these phones would have been used?

2.  On a less important note, has anyone seen one of these in a color other than black?

3.  Is there a (relatively) easy way to make a solid state EQ that could be used on the J/K/T?
« Last Edit: May 10, 2010, 11:08:32 PM by Jester »
Stephen

Offline paul-f

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Re: WE J/K-500, 5-52
« Reply #27 on: May 11, 2010, 12:20:35 AM »
An internet search for "resistor color codes" turns up a lot of tables and aids.  Here's a neat one:
     http://www.dannyg.com/examples/res2/resistor.htm

500T sets were renamed 500J or 500K in 1952.  Later in 1952 the 425B network came out in the 500C and 500D, so the earlier sets weren't needed.

Color started in 1953.  Therefore, any 500T, 500J or 500K sets found in color would have had a color change in refurb.
Visit: paul-f.com         WE 500  Design_Line

.

Offline Dan/Panther

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Re: WE J/K-500, 5-52
« Reply #28 on: May 11, 2010, 01:11:48 AM »
Paul;
I love that chart. I have a Radio Shack Cardboard wheel thing I got in highschool almost like that.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline benhutcherson

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Re: WE J/K-500, 5-52
« Reply #29 on: May 11, 2010, 12:07:09 PM »
Here are some photos of my 5-52 500T, for comparison. I find it interesting that I have a 500T made in the same month as the 500 J/K in this thread