332L Hum problem - UK Vintage Radio Repair and Restoration Discussion Forum

Dickie · 29th Sep 2014, 8:50 pm

I've just completed the refurb of a badly converted 332L that refused to ring out. This involved correcting the handset transmitter/receiver connections(!), correcting the internal links, and stripping, cleaning and retiming the dial mechanism. It's now able to receive and send calls without a problem. The only outstanding issue is a very obtrusive hum in the receiver. The transmitter looks like a type 21 electret inset. If I replace it with a conventional transmitter from a 746 the hum disappears and all's well, although it doesn't fit mechanically of course. Do I simply have a faulty transmitter and need to replace it, or is it more complicated than that?

ThePillenwerfer · 29th Sep 2014, 8:56 pm

Have you tried the 21 in the 746? If that 'phone starts humming you'll know it's faulty.

- Joe

Dickie · 29th Sep 2014, 9:07 pm

Doh! Why didn't I think of that? Just tried it and 746 starts humming. That answers my question. Thank you!

ThePillenwerfer · 29th Sep 2014, 9:35 pm

Always easier to see the wood from without the forest.

- Joe

dagskarlsen · 1st Oct 2014, 9:35 pm

Now you know the source, I have had some similar problems, disappearing at a raised voltage. Probably not easy to chive here, but it may be OK in another setup.

dsk

29th Sep 2014, 8:50 pm	#1
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	332L Hum problem I've just completed the refurb of a badly converted 332L that refused to ring out. This involved correcting the handset transmitter/receiver connections(!), correcting the internal links, and stripping, cleaning and retiming the dial mechanism. It's now able to receive and send calls without a problem. The only outstanding issue is a very obtrusive hum in the receiver. The transmitter looks like a type 21 electret inset. If I replace it with a conventional transmitter from a 746 the hum disappears and all's well, although it doesn't fit mechanically of course. Do I simply have a faulty transmitter and need to replace it, or is it more complicated than that? __________________ Regards, Richard, BVWS member

29th Sep 2014, 8:56 pm	#2
ThePillenwerfer Octode Join Date: Mar 2011 Location: Sheffield, South Yorkshire, UK. Posts: 1,453	Re: 332L Hum problem Have you tried the 21 in the 746? If that 'phone starts humming you'll know it's faulty. - Joe __________________ "Experts are only good at one thing: explaining why something will not work!"

29th Sep 2014, 9:07 pm	#3
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: 332L Hum problem Doh! Why didn't I think of that? Just tried it and 746 starts humming. That answers my question. Thank you! __________________ Regards, Richard, BVWS member

29th Sep 2014, 9:35 pm	#4
ThePillenwerfer Octode Join Date: Mar 2011 Location: Sheffield, South Yorkshire, UK. Posts: 1,453	Re: 332L Hum problem Always easier to see the wood from without the forest. - Joe __________________ "Experts are only good at one thing: explaining why something will not work!"

1st Oct 2014, 9:35 pm	#5
dagskarlsen Heptode Join Date: Jan 2008 Location: Hakadal, Norway Posts: 643	Re: 332L Hum problem Now you know the source, I have had some similar problems, disappearing at a raised voltage. Probably not easy to chive here, but it may be OK in another setup. dsk