UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Standard Beam Approach

jamesinnewcastl · 4th Feb 2021, 2:13 pm

Whooo Hoo - It works!

Hi - in the next post I have put links to YouTube videos of the refurbished R1125 working again! Well the first part at least....

I've rebuilt it so far onto a jig so that I can get into it with scope probes etc, and to make any soldering/replacements easier, pic attached.

What you see on the scope is the modulated output from the (rather splendid for the very cheap ebay cost) SSG1000 Farnell signal generator. The top trace shows the output of the first valve which is a "simple cumulative-grid detector with anode voltage controlled Reinartz reaction". This drives the second valve being an audio amplifier whose anode load is a transformer with two outputs, each of which is tuned to a different frequency namely 700 and 1700 c/s. Yes tuned - there are some hefty toroids in there.

So in the first video the system is powered up using the original motor/generator power unit (you can hear it powering up and running). The carrier frequency is slowly increased as you can see on the read out with the modulation at 1700 c/s. As the carrier hits the tuned frequency you can see the O or 'outer' neon strike on the pilots instrument (top right). The carrier is also pulsed in the actual system and I simulate this using the SSG1000 carrier on/off control. The pilot would normally just see this neon pulsing as he passed over the Outer marker.

The next video is the same but with the carrier modulation at 700 c/s, this time the I or Inner neon strikes - not quite so bright for some reason.

Technically this is not great achievement nor is the circuit anything to write home about but I hope to show soon that it also generates the warning audio for the pilot and acts as an audio amplifier for other parts of the system. Not bad for a couple of valves.

Later, one day, I hope to restore the remainder of the system with the guidance signals operational and everything back in place!

Cheers
James

4th Feb 2021, 2:13 pm	#13
jamesinnewcastl Heptode Join Date: Jul 2009 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 723	Re: Standard Beam Approach - Rebuild update Whooo Hoo - It works! Hi - in the next post I have put links to YouTube videos of the refurbished R1125 working again! Well the first part at least.... I've rebuilt it so far onto a jig so that I can get into it with scope probes etc, and to make any soldering/replacements easier, pic attached. What you see on the scope is the modulated output from the (rather splendid for the very cheap ebay cost) SSG1000 Farnell signal generator. The top trace shows the output of the first valve which is a "simple cumulative-grid detector with anode voltage controlled Reinartz reaction". This drives the second valve being an audio amplifier whose anode load is a transformer with two outputs, each of which is tuned to a different frequency namely 700 and 1700 c/s. Yes tuned - there are some hefty toroids in there. So in the first video the system is powered up using the original motor/generator power unit (you can hear it powering up and running). The carrier frequency is slowly increased as you can see on the read out with the modulation at 1700 c/s. As the carrier hits the tuned frequency you can see the O or 'outer' neon strike on the pilots instrument (top right). The carrier is also pulsed in the actual system and I simulate this using the SSG1000 carrier on/off control. The pilot would normally just see this neon pulsing as he passed over the Outer marker. The next video is the same but with the carrier modulation at 700 c/s, this time the I or Inner neon strikes - not quite so bright for some reason. Technically this is not great achievement nor is the circuit anything to write home about but I hope to show soon that it also generates the warning audio for the pilot and acts as an audio amplifier for other parts of the system. Not bad for a couple of valves. Later, one day, I hope to restore the remainder of the system with the guidance signals operational and everything back in place! Cheers James Attached Thumbnails Last edited by jamesinnewcastl; 4th Feb 2021 at 2:20 pm.