#1
|
|||
|
|||
Headphone/microphone hearness for # 19
I am trying to test out old dried up spare headphone sets and hopefully understand how they work.
I need a schematic of the wiring as I am totally frustrated. I have rigged up an old transistor radio to provide the suitable signal from the earphone jack. My frustration is that I can make the earphone work if I connect directly to the earphone contacts but cannot make them work from the brass contacts on the rubber snatch plug. There are 5 wires in the loom .... black-white-red-blue-green...... I suspect one wire does double duty or something..... Black goes from snatch plug to one connection on the earphone(1) them doubles back to the microphone. A blue goes from the other connection of the same earphone(1) to the other earphone(2)... the other contact of earphone(2) is green........ but if I apply power/sound to the black and green wire of the snatch plug it does not play. To the microphone goes 4 wires.... white-red-black and blue..... Or am I going cross eye and colour blind.... Bob C. a.k.a sparky on training wheels.
__________________
Bob Carriere....B.T.B C15a Cab 11 Hammond, Ontario Canada |
#2
|
|||
|
|||
The ear pieces are wired in series so if you can hear sound when radio is applied to each then then headset portion works. The microphone + goes to the white wire, The mic - goes to one of the switch contacts in the handset. The other side of this switch goes to the red wire.
The black is common to the headset and another switch contact. Other side of headset goes to green wire and the other side of the switch goes to blue. The contacts on the snatch plug corrode quit easily so they should be cleaned. Try not to use anything abrasive like sandpaper or steel wool. If still not working you can pull the rubber boot of the rear of the plug to see if any wires are broken. |
#3
|
|||
|
|||
Quote:
There are (approximately) three varieties of headset assembly around: No.1 - with a bakelite "lollypop" microphone (Microphone, Hand, No.7). No.2 - with a grey-painted cast alloy microphone - this is for intercom use only with the Junction Distribution No.1 or No.2 fitted in early AFVs, it's a double-button carbon microphone that requires a 12 volt supply and a transformer. No.10 - with a "fist" microphone, either brown painted metal (Canadian) or circular Bakelite (British - Microphone, Hand, No.13). No.1 or No.10 are the types you need for use with the WS19. You may also need to clean the (microphone and pressel switch) contacts inside the microphone body before that will work properly. Hope this is some help. Chris. |
#4
|
|||
|
|||
Thanks for your response guys.....
But I still have questions....
Bruce thanks for the schematics.....much better than the crude one I drew up . ... I have used DeOxit on the brass contacts but did not seem to clean up much....... I may try the old "Brasso" next with a light touch. Also I have both the No 1 Lollipop and the Big bulky No 10 fist type. For the sake of this discussion I will focus on the lollipop type. I actually had a No 1 that was so dried up it was useless.... so I broke up the snatch plug and removed some section of cloth covering to see wiring color and physicaly and visually trace properly.... One more basic observation on the color wiring scheme Referring to Bruce's schematics... top right hand corner. When looking at the snatch plug as shown on the schematic... Pin no 1 is Blue Pin 2 is Green 3 is Black 4 is White 5 is Red So is it correct to say power comes from connection A in the control box to pin 2 Green on the snatch plug.... goes through the earphone wired in series and back by means of the Black wire (common/ground) pin 3 and connection C.......?....... so applying power to pin 2 and 3 on the plug should give me sound on BOTH earphones....? which I can't get !!!! Now for my observations/questions......please be patient.... When I apply power from the earphone cable from the radio to the RH earphone (RH on the schematic) directly to the two screws the RH earphone works. When I apply contacts to the black brass no 3 in the plug and the other to the screw of the RH earphone it works. If I apply the same source of power directly to the LH earphone it will NOT work....... I have done the same process to another no 1 and 2 other no 10 with the same results.... only one earphone can be powered. I can establish contact with the pin no 3 black on the plug on all other 3 set BUT cannot connect power to any of the other contacts and get sound. Leaving out pin 4 and 5 .. white and red.... I only have 2 other possibilities the blue or green..... but the blue seems to be cut off by the microphone switch.. I cannot understand why I cannot get sound off the LH earphone..... not all 3 sets could not be defective..... If they are wired in series..... if I applied power to the RH black earphone and to the green wire leaving the LH earphone I should have sound coming out of both earphone..... but I get nothing...? Why can't I ear sound from the LH earphone when I connect power directly to both screws/contacts of the earphone...? but it works on the RH earphone. Is my power source from the transistor radio too weak to power both earphones...... Remember I repeated the same negative results on 3 other sets besides the one I took apart....? I am sure glad not to be working with High Tension wiring as I would be fried by now. Speaking of fried.... last Saturday when I had friends over to chat about WS 19 sets I showed them a Dynamotor that my Dad had used in the 50s/60s to engrave his initials on his tools using the HT 2 of the Dynamotor. So I fired it up with a CPP-2 power supply and the Dynamotor wirled into life......on 550v you can put the two HT alligator clips together than slowly pull them apart with a nice white/blue steady spark for about 5 or 6 mm before it stops..... I was encouraged to turn if off and put it away. Awaiting your comments and guidance. Bob C.
__________________
Bob Carriere....B.T.B C15a Cab 11 Hammond, Ontario Canada |
#5
|
||||
|
||||
Doctor Frankenstien
Quote:
Thanks for hosting the session. It was, well, electrifying.
__________________
RHC Why is it that when you have the $$, you don't have the time, and when you have the time you don't have the $$? |
#6
|
|||
|
|||
I tested a #10 headset using an ohmmeter and there was continuity between pins 2 & 3. There was continuity across the right hand earphone and the left hand earphone, measured at the screws.
Take your multimeter and use the low ohms range (I trust you have one ) Measure from the common to test points 1, 2 & 3. If 1 is good then there is continuity across right headphone. Go to point 2. If good fine but if open there could be a break in wire between earpieces. If 2 is good then measure point 3. At each point your should have a low resistance reading. Using the ohmmmeter is a better way to test the headset & cables than listening to CBC. If the set measures high resistance (open circuit) then scrub down & prepare for surgery. Are the headset's Canadian (Chamois cushions)? |
#7
|
|||
|
|||
Thanks Bruce
....back to the work bench to play with the Ohm metre.
Bob C.
__________________
Bob Carriere....B.T.B C15a Cab 11 Hammond, Ontario Canada |
#8
|
|||
|
|||
I am back with test findings....
I Bruce.... last question first......
The lollipop No 1 that I am carefully disecting has some kind of black velvet removeable covers.... The other 2 No 10 have the chamois and another relatively new acquisition No 1 also has chamois on the ear pads. To prevent confusion I will stick to the disected No 1 set. See the attached picture of my findings..... note that I have added a letter A for the post on the RH earphone....then continued to the other 1, 2, 3 and added a Post plug 2 for the end return to the plug. ...so the left hand earphone seems to be open..!!! Before I put on the gloves for internal surgery to the LH earphone....... ....when I played the radio through the RH earphone and went on to connect directly to the post 2 and 3 of the left hand earphone NO sound came out.... i.e. infinity readings. Now without taking apart the other earphone sets I got the same results from the 2 No 10 sets.... one earphone plays loud and clear the other is dead.... just a coincidence...? Two other things I discovered.... One.... I took the microphone apart and applying the power source from the radio to the mic. I can hear clearly the sound coming from the metal mic set.... so that works..... Two..... The new relatively new old stock headset from the USA..... has a different black/red tracer cloth covering....with chamois on the earphone No 1 lollipop..... and the earphone works with the radio source.... BUT still only one earphone works...... AND I can trace/play the radio sound BUT by touching the post 2 green on the snatch plug instead of the common black no 3..... no response from the black post 3..... Final questions.... are there any fuses inside the control box used on the wooden board for training... the control box has the 3 earphone connectors coming out the side and in the parts manual is referred to as .... control unit 3A MK II.. What's next Doctor...?? Bob C.
__________________
Bob Carriere....B.T.B C15a Cab 11 Hammond, Ontario Canada |
#9
|
|||
|
|||
Quote:
On the headset front, check the earpiece continuity with an ohmmeter, infinity means it's duff, remove and faulty ones (undo the nuts and disconnect the wiring then spring the headband clips to remove the earpiece from the headband), and replace the faulty one with a "known good" earpiece from another headset. Chris. |
#10
|
|||
|
|||
Ready to operate....
...will disect the earphones tomorrow when the sun shines in the work room.....
Thanks for your help.....stay tuned. Bob C.
__________________
Bob Carriere....B.T.B C15a Cab 11 Hammond, Ontario Canada |
#11
|
|||
|
|||
Dissection complete.
Found a "minute" wisker of copper that WAS formerly connected to the voice coil..... broken....and so small as to make it impossible to mend..... copper wire is finer than a human hair.
So there were no continuity acroass the two ear piece..... which explains why only one earphone worked. Much like when I dissected frogs in class I could never put the frog together again.... so that earphone is Kaput!! Now will turn my attention to a more complete NO 1 set with chamois covers..... it also only works on one earphone..... but will tread lightly and not do a full irreversible dissection. Meanwhile I have opened up the control box and using the previous schematic I beleive that I can installattach a more modern earphone, so looking at installing a 1/4 male/female jack. This should allow me to test further the rec/trans. and see if it work properly. I fear that most of the rubber bellshaped connectors have corroded contacts and the rubber is as hard and brittle has hard wood. They may look OK for a static display but for actual use very impractical. I know of no means to make the rubber soft again. Installing a jack or having a female jack hang out of the control box is relatively easy as the boxes already have two soft rubber plugs to pass the wired through. Bob
__________________
Bob Carriere....B.T.B C15a Cab 11 Hammond, Ontario Canada |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Headphone sets for tank crew? | kevinT | WW2 Military History & Equipment | 0 | 21-01-06 20:34 |