Unable to hear on phone

[Paul Boomer]

 DSK,

I Ohm checked all the wires and coils after disconnecting each component and they all have continuity, there must have been oxidation on some connection because now I can barely be heard on the other phone and before I couldn't be heard at all. I can hear fine on mine in the shop. What is the max batt voltage that these phones can handle or will that make a difference? One phone Batt is 3.5V and the other is 3.04V.

Is the Batt in the phone to boost the signal coming into the phone or to boost the signal out of the phone?

Thanks Paul

[dsk]

The battery is for the transmitter circuit only, and whats inside the transmitter capsule is depending on the current, the current is pressed trough by voltage.  Usually such telephones use 3V batteries, and that will push trough a current of 18-35 milli-amp, more may fry the carbon granulates in the transmitter. 


The battery voltage should not drop under 2.5 V when it is in use. disconnected the voltage does not tell us much, at least not when it is 2.9V or more.

The receiver should work perfect with no batteries in the phone.

If the phone has been in a corrosive environment oxidation may be on several locations, most likely in the hook-switch  contacts.  Do not use file, or sand-paper on these. Regular dry paper strips from normal printer paper will usually be enough. 

If you test by using a screwdriver and short the contacts close to where the wires are soldered you will hear a difference if they need to be cleaned.

It is no risk to touch, or short those with a screwdriver for just some seconds, or minutes, in worst case you draw current from the battery as regular use in off hook position. 

dsk

[Paul Boomer]

  So the battery voltage should be checked in the off hook position? I'll check that.   Paul