Author Topic: Kellogg 925 feedback problem  (Read 1309 times)

Offline cloyd

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Kellogg 925 feedback problem
« on: November 07, 2016, 09:56:54 AM »
Hello all,
Callers complain that they are getting an echo on their end when I use my 925 phone.  Can anyone shed some light on how to fix the problem?  I bought the phone off of ebay so if anyone recognizes it as their former phone, I would love to know any history they have for it.
-- I am always doing what I cannot do yet, in order to learn how to do it. - Van Gogh -- 1885

Offline cloyd

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Re: Kellogg 925 feedback problem
« Reply #1 on: November 07, 2016, 09:58:14 AM »
More pics than you need but I know how much I enjoy the photos!
Thank you,
Tina Loyd
-- I am always doing what I cannot do yet, in order to learn how to do it. - Van Gogh -- 1885

Offline TelePlay

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Re: Kellogg 925 feedback problem
« Reply #2 on: November 07, 2016, 11:44:42 AM »
Oh, so nice and clean . . .

Thanks for posting the ringer picture. Nice to see what the bias spring looked like on the ringer coming out of the factory.
            John . . .

              

Offline cloyd

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Re: Kellogg 925 feedback problem
« Reply #3 on: November 07, 2016, 11:56:42 AM »
John,
Yes, it is nice and clean but that is the shape that I received it in.  It's nice to receive something that has already had that attention given to it.

I can post a better picture of the ringer too.  Glad it is helpful!

Tina
-- I am always doing what I cannot do yet, in order to learn how to do it. - Van Gogh -- 1885

Offline dsk

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Re: Kellogg 925 feedback problem
« Reply #4 on: November 07, 2016, 02:22:14 PM »
Not sure if it helps, but try to move the wire from terminal 6 to7 on the induction coil (transformer).
This should make the phone better tuned for shorter loops.

dsk

I have even got a regular New York number :-) 646 570 1796

unbeldi

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Re: Kellogg 925 feedback problem
« Reply #5 on: November 07, 2016, 05:32:13 PM »
Your Kellogg set looks terrific.
It was used in the US Armed Forces Signal Corp.  There it was known as the TA-102/FTC.  The Kellogg model number they used was 925BAX, but they changed the dial to an Automatic Electric dial with a special contact arrangement, TA-45/GT.


Echo is usually a sign of impedance mismatch. I am assuming your speaking partners are hearing their own voice delayed?  How are you connecting the telephone?  On a PBX or on a telco line? 
« Last Edit: November 07, 2016, 06:23:12 PM by unbeldi »

Offline cloyd

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Re: Kellogg 925 feedback problem
« Reply #6 on: November 07, 2016, 06:21:27 PM »
Your Kellogg set looks terrific.
It was used in the US Armed Forces Signal Corp.  There it was known as the TA-102/FTC.  The Kellogg model number they used was 925BAX, but they changed the dial to an Automatic Electric dial with a special contact arrangement, TA-45/GT.


Echo is usually a sign of impedance mismatch. I am assuming your speaking partners are hearing their own voice delayed?  How are you connecting the telephone?  On a PBX or on a telco line?
Thank you, yes, I lucked out and got a nice one for a change!  The dial plate is shiny metallic too.  Very attractive.  I am connecting the phone on my PBX Panasonic 616.  I hope you have an easy solution for me!
Tina
-- I am always doing what I cannot do yet, in order to learn how to do it. - Van Gogh -- 1885

Offline cloyd

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Re: Kellogg 925 feedback problem
« Reply #7 on: November 07, 2016, 06:22:57 PM »
Not sure if it helps, but try to move the wire from terminal 6 to7 on the induction coil (transformer).
This should make the phone better tuned for shorter loops.

dsk

Thank you for the input.  I welcome all suggestions!
Thanks,
Tina
-- I am always doing what I cannot do yet, in order to learn how to do it. - Van Gogh -- 1885

unbeldi

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Re: Kellogg 925 feedback problem
« Reply #8 on: November 07, 2016, 06:25:50 PM »
I am not sure that your dial is in fact the TA-45, since yours has 4 springs, instead of 5.

But here is the diagram from the Army manual TM-11-468.  Make sure the wiring is correct on your set.



unbeldi

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Re: Kellogg 925 feedback problem
« Reply #9 on: November 07, 2016, 06:32:55 PM »

From  the diagram we see that dsk's idea of disconnecting screw #6 in fact disconnects the anti-sidetone correction. It will certainly change the impedance of the receiving end slightly, but I don't see that will change line echo.   The impedance of the set is primarily given by the primary side of the induction coil and the transmitter.

Do you have another Kellogg phone from which you can swap the transmitter for testing ?


Offline dsk

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Re: Kellogg 925 feedback problem
« Reply #10 on: November 07, 2016, 11:59:11 PM »
According to the diagram in "Old-Time Telephones" of Ralph O Meyer the terminal no 7 is to a resistor between 6 and 7. The resistance of this should be 62 ohms. This action will not only reduce the sidetone damping, but the booster effect too.  If the coil has no resistor (resistor winding) both the sidetone damping and the booster effect will be totally removed This may remove the echo, but give the unpleasant feeling of having no damping of your own voice. Trying with different resistor values will in this case tune it to perfection.  On a 616 you will have a short line and may need to ad just the phone.

dsk

I have even got a regular New York number :-) 646 570 1796

Offline Phonesrfun

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Re: Kellogg 925 feedback problem
« Reply #11 on: November 08, 2016, 12:31:32 AM »
Maybe someone with more knowledge of the 616 can chime in here and tell me if I am off base or not.


Doesn't the Panasonic 616 provide its own local loop and effectively isolate the phone from the outside line?  If that is the case would small impedance differences between a Kellogg 925 and, say a WE 302, or even a WE 500 even matter unless the Panasonic could not handle the mismatch?  I wonder what the difference would be to connect the 925 directly to the phone line. 



-Bill G

unbeldi

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Re: Kellogg 925 feedback problem
« Reply #12 on: November 08, 2016, 09:34:34 AM »
Maybe someone with more knowledge of the 616 can chime in here and tell me if I am off base or not.


Doesn't the Panasonic 616 provide its own local loop and effectively isolate the phone from the outside line?  If that is the case would small impedance differences between a Kellogg 925 and, say a WE 302, or even a WE 500 even matter unless the Panasonic could not handle the mismatch?  I wonder what the difference would be to connect the 925 directly to the phone line.

I think that is very valid, and yes, the PBX station lines are electrically isolated from the CO lines by 1:1 transformers, unless the power fail mode is active on the PBX, when the first six stations are directly connected by relays.
But we have to assume that she already tested that it is is only the Kellogg set that has this problem.  I do find it odd that there would be any echo on a short station line no matter how mismatched the impedance is.

Hmm, is this echo problem perhaps restricted to a specific caller ?


Offline dsk

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Re: Kellogg 925 feedback problem
« Reply #13 on: November 08, 2016, 11:08:10 AM »
I have never had this problem on the Pansonic, on POTS line, but when I connected the Panasonic to my PAP2T I had one phone causing echo, It was no bolt in adjustments on that old Norwegian phone, but it disappeared when i put in a 220 ohms resistor in series with the phone, but weaker sound too, adding a 2.2 micro-farad capacitor in parallel with the resistor made the incoming signal stronger, and everything worked well.  The circuit of this telephone was based on the same circuit as the w.e. 302.
Here it seems to be a built in possibility by moving a wire, so why not try? 

dsk

I have even got a regular New York number :-) 646 570 1796

unbeldi

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Re: Kellogg 925 feedback problem
« Reply #14 on: November 08, 2016, 11:31:34 AM »
I have never had this problem on the Pansonic, on POTS line, but when I connected the Panasonic to my PAP2T I had one phone causing echo, It was no bolt in adjustments on that old Norwegian phone, but it disappeared when i put in a 220 ohms resistor in series with the phone, but weaker sound too, adding a 2.2 micro-farad capacitor in parallel with the resistor made the incoming signal stronger, and everything worked well.  The circuit of this telephone was based on the same circuit as the w.e. 302.
Here it seems to be a built in possibility by moving a wire, so why not try? 

dsk

Ah, you are correct in that the anti-sidetone balance of the 925 triad circuit is actually on the transmitter side, not the receiver side.  The receiver circuit is just the secondary winding with a condenser and receiver is series. This is the reason that this circuit uses three capacitors.  The anti-sidetone balance on these is accomplished across the transmitter.