Circuit board But what for ? - UK Vintage Radio Repair and Restoration Discussion Forum

60 oldjohn · 25th Nov 2021, 11:41 pm

The three transistors are 2N2369. What is it ?

John.

turretslug · 26th Nov 2021, 12:27 am

Wideband noise source, amplifying the AC component of whatever the Zener (?) is doing?

joebog1 · 26th Nov 2021, 12:29 am

I thought FM transmitter ??.

Joe

Terry_VK5TM · 26th Nov 2021, 4:34 am

Impedance meter for antenna's (amateur style) - not quite sure why it needed a fuse though.

The three transistors and zener diode on one side is indeed the noise source and the pot and toroid wound transformer forms part of the balance arrangement - the pot would have a knob over a scale marked in ohms.

The "detector" - for the balance null - for these things was usually a radio receiver.

Stockden · 26th Nov 2021, 8:33 am

Terry is right, it’s a “Cambridge Kits” RF noise bridge. I have one somewhere that I made long ago (1970s?). If I can find mine I’ll post a picture of it.

Hugh

60 oldjohn · 26th Nov 2021, 1:54 pm

Thank you everyone, I now see plenty about them on the net. I am offering this in the sales section.

John.

25th Nov 2021, 11:41 pm	#1
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Circuit board But what for ? The three transistors are 2N2369. What is it ? John. Attached Thumbnails __________________ My favourite text message "I'll be there in five minutes, if not read again"

26th Nov 2021, 12:27 am	#2
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,400	Re: Circuit board But what for ? Wideband noise source, amplifying the AC component of whatever the Zener (?) is doing?

26th Nov 2021, 12:29 am	#3
joebog1 Banned Join Date: Jun 2015 Location: Mareeba, North Queensland, Australia Posts: 2,704	Re: Circuit board But what for ? I thought FM transmitter ??. Joe

26th Nov 2021, 4:34 am	#4
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,342	Re: Circuit board But what for ? Impedance meter for antenna's (amateur style) - not quite sure why it needed a fuse though. The three transistors and zener diode on one side is indeed the noise source and the pot and toroid wound transformer forms part of the balance arrangement - the pot would have a knob over a scale marked in ohms. The "detector" - for the balance null - for these things was usually a radio receiver. __________________ Terry VK5TM https://www.vk5tm.com/

26th Nov 2021, 8:33 am	#5
Stockden Heptode Join Date: Mar 2008 Location: Forest of Dean, Gloucestershire, UK. Posts: 648	Re: Circuit board But what for ? Terry is right, it’s a “Cambridge Kits” RF noise bridge. I have one somewhere that I made long ago (1970s?). If I can find mine I’ll post a picture of it. Hugh

26th Nov 2021, 1:54 pm	#6
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,988	Re: Circuit board But what for ? Thank you everyone, I now see plenty about them on the net. I am offering this in the sales section. John. __________________ My favourite text message "I'll be there in five minutes, if not read again"