UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Telephony and Telecomms

Notices

Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment

Closed Thread
 
Thread Tools
Old 27th Apr 2017, 8:24 pm   #1
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default Mic won't work on Tele 310

As above, I just can't get the mic to work. Have tried the handset on a different phone and it works fine so it can't be that. I've traced out all the connections on the phone and get continuity on everything. I also get a dial tone. I've bridged out the dial between D4 and D5. A visual inspection shows the wiring to be in good condition. The only odd measurement was around 50 ohms on the induction coil between 3 and 4.

I'm guessing I might have to solder in a new induction coil but I just wanted to make sure I wasn't missing anything obvious.

On the diagram (N410) I've connected my phone cords to T1 and T8 and bridged T1 and T2. I've got my own PBX.

Any ideas?
els1967 is offline  
Old 27th Apr 2017, 9:19 pm   #2
ThePillenwerfer
Octode
 
ThePillenwerfer's Avatar
 
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
Default Re: Mic won't work on Tele 310

To be honest I can't make much sense of N410. However, similar instruments have the 75Ω part of the coil in parallel with the receiver and 30Ω non-inductive resistance which would lower the resistance reading between coil terminals 3 and 4 if these weren't disconnected first.
ThePillenwerfer is offline  
Old 27th Apr 2017, 9:30 pm   #3
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default Re: Mic won't work on Tele 310

Ok thanks.
els1967 is offline  
Old 29th Apr 2017, 3:27 pm   #4
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default Re: Mic won't work on Tele 310

Traced it to a short on the 0.1uF cap. thus shorting out the speech network. Odd as it's not often these fail. Does anyone have a spare square one?
els1967 is offline  
Old 29th Apr 2017, 4:03 pm   #5
ThePillenwerfer
Octode
 
ThePillenwerfer's Avatar
 
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
Default Re: Mic won't work on Tele 310

Thanks for the up-date; I'd been wondering about it.

I doubt it would matter if you left that cap disconnected. You could also replace it with a normal modern one, but it's a different matter if you want to keep things original. Another option would be re-stuffing as there'd be plenty of room.
ThePillenwerfer is offline  
Old 29th Apr 2017, 4:42 pm   #6
russell_w_b
Dekatron
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,684
Default Re: Mic won't work on Tele 310

All that cap is for is to bypass any RF if you're located near a transmitter and the carbon mic decides to act as a demodulator.
__________________
Regds,

Russell W. B.
G4YLI.
russell_w_b is offline  
Old 29th Apr 2017, 9:36 pm   #7
els1967
Pentode
 
Join Date: Aug 2016
Location: Dunstable, Bedfordshire, UK.
Posts: 139
Default Re: Mic won't work on Tele 310

Well the most interesting part was finding the fault. I've got a few spare GPO caps around, prob. will fit one then shove it in the attic tbh.
els1967 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:53 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.