I have never tried for real before, but todays experiment seems to work.
I used a diode to short out the unit if the polarity gets wrong. it works from approx 4volts, and it has only 5 components.
enclosed pictures:
dsk
I have five "daily drivers" deployed and use them constantly. Three D1/202's and two 302's. The carbon transmitters in all of them (three F-1's and two E-1's) have been replaced with amplified electronic mic/transmitters. Not good I guess from a purist/collector point of view, but a vast improvement in functionality while keeping the "stock" look. My callers say incoming voice is astonishingly clear.
I had a hope of getting this working on a LB phone with 3V battery, but, no! I need 3 elements. Well it works! :-)
dsk
Sharper photos, I hope.
dsk
DSK:
Pretty small unit. Do you have a picture of the finished product in actual use?
I have to try it out, and see if it really keeps on working.
dsk
I tried this but found that it didn't work very well. I'm not saying there's anything wrong with it, just that it's not suitable for my equipment.
I have however come up with a slightly more complicated version that works very well. It's still simple enough to make 'dead-bug' style.
A zip is attached which contains PCB details.
I had forgotten this thread, no it did not turn out as suitable for me. I might have used diodes with too high voltage drop, or done bad soldering, but no. No good!
dsk
INTERESTING INDEED!
I was recently very curious about the "carbon Mic replacement" mics at payphone.com which would seem to fit in a 500 handset. This means I can test this with the F1 as well.
Mark
I have found some replacement capsules: http://www.classicrotaryphones.com/forum/index.php?topic=23321.msg233918#msg233918 (http://www.classicrotaryphones.com/forum/index.php?topic=23321.msg233918#msg233918)
But for phones that operates on low voltages, they are not suitable.
Most field telephones and local battery telephones may have room for different batteries, so when changing transmitter it may be needed to change batteries.
Some older German phones has a current consumption in the sidetone balancing network making it difficult. Soldering in extra resistor+capacitor may solve it. Then the question is. Is that change of the phone worse than only putting in an transistorized capsule? It is reversible, but you need to solder.
dsk
One of my jobs at the transit authority was to build handsets for the train communications systems. I had to sometimes find sources for the components used in them. I remembered one of them carried electret microphone cartridges to replace carbon cartridges. Would any of these be of any value?
http://telephonecomponents.com/transmitters.html
At COT we would get a unit from Audiosears that was similar to the EMS 94 on the link WE would replace the carbon microphone and cup in a G type handset. I would dissassemble the unit and use the printed circuit in tight spaces in some handsets
Thank you for sharing more info.
dsk
Now, I have been playing around with some transistorized transmitter capsules, on on some phones dialing gets trouble, on some systems (ATAs) a shunting resistor may solve it, on others not, or has to be of so low resistance that the transmission volume is considerably reduced.
The capsules I have tested are made for German phones (W48 ish circuit) and those have enough shunting the transmitter with their bridge circuits.
dsk
The designs that give you dialing issues must be those that do not have a shunt contact shorting out the transmitter?
No, but in that moment the dial goes to rest position the transmitter use some time to increase the current from 0 and that is enough to make trouble for e.g. the old PAP2 ATA from Linksys. Putting in a carbon transmitter and everything works, but of course with the typical carbon transmitter sound. A 330 ohms resistor across the transmitter reduce the transmitters output in the system, but it helps. Maybe a zener diode may solve it? I just do not have the right one here, it should be rated something like 4 volts.
dsk
Ah, now I can see what the problem is.
Some of the German transmitter capsules have a 5.1 Volt zener diode built in. I found one in a brown AKG DKO48 at least.