Sidetone Differences On My 500's

[rp2813]

I'm curious about why one of my mid 50's vintage 500's would have a higer and very noticeable level of sidetone than all of the others I own or have used, which range from 1950-1959.  Is there a particular component that would cause this condition?  It's not super bothersome, my voice definitely comes though loud and clear which indicates I've got a nice transmitter capsule in it, but I've never noticed this amount of sidetone in a 500 before.  Not as bad as my 202 but also not typical of a 500, I think.

Any ideas?

Thanks

Ralph

[McHeath]

What network does that 500 have? 

I have a 1951 500 with a 425A that has much louder sidetone than my other 500s.  So much so that it's annoying and I had to add a resistor to the handset cord to reduce it.  The old BSPs say to simply replace the network when sidetone is objectionable, not much help though when we don't really want to do that today. 

[JorgeAmely]

Colin T. Chambers, the owner of the website www.oldphoneguy.com ( dead link 03-18-22 )  and author of the document titled "Building telephone testers and learning how to use them" has an excellent and easy to understand ( ) explanation on how anti-side tone networks operate. The document is available from his website.

I read it a couple times and from I was able to understand (page 48 and on), the network electrically emulates the way the outside phone line looks like to aid in reducing your own voice level. If some of these electrical components have degraded over time or are somehow out of tolerance to start with, then this phone would be less capable of reducing the level of your own voice on the speaker. That alone would make it a candidate for network replacement.

[Phonesrfun]

I agree with everything that has been said.  The network in a 500 is not at all serviceable and needs to be replaced if bad, and that would entail drilling out the rivets to take the old one off and then using pop rivets or screws to replace it.

I'd probably just live with it rather than going through all that.

One precautionary thing to do before tearing into the phone would be to check the wiring to make sure it is wired correctly.

-Bill

[rp2813]

Thanks guys.  I was going to inquire if it was the network at fault but thought another component would be a more likely suspect.  It's not that bad but as I stated, it is noticeable and made me curious.  This phone will likely be taken out of service and replaced with a 2500 at some point, so I won't do anything to it.  It's not worth replacing the network since it's a matching dates mid-50's phone.  It doesn't have the 425A network.  My 10/50 phone has a 425A and no sidetone issues at all.

Ralph

[JorgeAmely]

Bill:
Wasn't you who said that the early networks used light bulb filaments as part of the network to adjust the volume based on the distance to the CO?

Perhaps the tiny bulb filament broke due to impact many moons ago.

I would use another 500 and retire this one. Pretty much anyone that owns a 500, owns a few more.

OK, time to confess. How many WE500s do you have at home?

[Phonesrfun]

Bill:
Wasn't you who said that the early networks used light bulb filaments as part of the network to adjust the volume based on the distance to the CO?

It wasn't me, but.....Not a bad analogy.

Only the early 500's with the 425A network and with a separate compensating network had such a variable resistor.   It would heat up based on the amount of current going through it, which was a function of distance from the central office.  The heat in turn affected the balance of the network to self compensate for the distance.  This method was replaced early on with the later 425 series networks that used varistors.

But, I believe rp2813 has indicated the phone in question does not have the early 425A network. 

-Bill

[Dan/Panther]

rp2813;
Why not simply switch the transmitter element with one from another phone, to see if that is the component that is given you the over sensitive sidetone.
If another element works fine, you won't need to change the network.
Has anyone ever pulled the cover from a network to see if they can be repaired without removing them, maybe replace all the insides. Leave the case intact, and retain the original dates ?
D/P

[Phonesrfun]

The potted WE 500 networks are filled with a very obnoxious gel-like goo that makes them very hard to do anything with.   Check it out on a junker 500 phone sometime.  Besides that, the varistors are custom made, and of course, the induction coil is also custom.  About the only off the shelf things in a WE network might be the resistors and capacitors.

-Bill

[JorgeAmely]

I once opened a 425B network.

Remember the movie Alien, when the monster open his/her mouth?

[Phonesrfun]

Dan/Panther:

I guess I should have read your whole post before I posted mine.  Your idea of removing the lid which has all the items soldered to it does have merit.  It could be removed as a unit which would entail just bending the tabs open to lift it up and off.

However, you still have to deal with the alien saliva part that Jorge and I have referred to.  It is very thick, gooey, and smells like mildew.  If you thought the innards of a soft plastic 302 smelled bad, try the 425 network goo.

I am sure one could do it, and it would not be as hard as bleaching or sanding a phone.


-Bill

[JorgeAmely]

Bill:

Back then they did not publish the MSDS (Material Safety Data Sheet ) of the stuff inside the network, let alone the early AE80 network.

Do you know if these things are safe to touch?

[Phonesrfun]

I think it is probably inert, but really, I have no clue.  I have touched it before, but that was many, many years ago, and I still have all fingers.

-Bill

[Dennis Markham]

Every now and then when I remove the network screws the tips of them have the sticky substance on them.  It is difficult to remove but it has never harmed my skin.

[McHeath]

Last year I pulled the top off a 425B and was curious about that slime as well.  Nowhere have I been able to find out what it is, perhaps cosmoline which looks similar and will endure for decades as well. 

I have thought that you could replace the top of a network which will replace any bad components and keep the riveted shell.