Repairing my vacuum tube-based RF signal generator from the 60s

Рет қаралды 3,629

Күн бұрын

I had a Leader LSG-10 RF signal generator laying around for quite a while which wasn't getting a lot of use because the modulation wasn't working. In this video I show you the device and I try to repair it.
00:00 Introduction
01:42 How to use the signal generator
09:14 Disassembly
10:23 Identifying the death caps
13:04 Overview of the circuit
17:54 Measuring voltages & checking capacitors
22:38 Swapping death caps
24:10 Remaining swapped components
26:04 First powerup & checks
29:38 Modulation test and repair
35:47 Repair finished & outro
WARNING: Do not attempt to repair electronic equipment if you don't know what you're doing.
If you enjoy my content, consider buying me a coffee:
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Full playlist for the restoration of the Telefunken Operette 6:
• Telefunken Operette 6
Electrocution logo:
Nesdon Booth, The Noun Project
License codes:
FHB6IHBWOF6MUCVP

Пікірлер: 24

@terryblackman6217 Жыл бұрын

Good morning Kristof. I very much enjoyed today's video, I find it so refreshing seeing the restoration of a piece of vintage test gear. Thank you for sharing. Terry

@retro_tech Жыл бұрын

Thanks a lot!

@hardlygamaliel455 Жыл бұрын

I may have an explanation of why the audio oscillator suddenly started working. Oscillators rely on having enough feedback to overcome losses in the circuit. In this circuit the feedback is set by the 0.02 uF and the 0.1 uF capacitors. I believe that the oscillator may be "right on the edge" with just enough feedback to start (sometimes) but not reliably. This could be either due to the values of the capacitors changing or to the 6AR5 tube getting "weak" over time.

@retro_tech Жыл бұрын

That sounds logical. I suspect the capacitors. Maybe after a bit of use, they were "worn in" again and performing again above the threshold to get the oscillator starting. In any case I swapped them because they were quite significantly out of spec.

@DavidLindes Жыл бұрын

So interesting to see all this circuitry (even if it is fairly simple) without any circuit boards! I guess I haven't cracked open enough vintage gear... this is totally novel to me. :) Interesting restoration; thanks for sharing!

@retro_tech Жыл бұрын

Thanks! You should see a tube radio then... 😄

@DavidLindes Жыл бұрын

@@retro_tech haha, I guess I should! Perhaps I'll dig around on your channel a bit. :) 73s!

@michaelmacdonald3408 Жыл бұрын

That cap that was faulty started to reform but yes replace all those paper caps not worth mucking around.

@retro_tech Жыл бұрын

Indeed.

@LaserGuy64 Жыл бұрын

Thanks for the nice content!!

@retro_tech Жыл бұрын

Thanks!

@justicelut Жыл бұрын

I have the lsg11 model. Replaced the selenium with two diodes for full wave rectification, also earthed the chassis to mains ground. A Zener diodes regulates the full wave to 75 volts for the ht. they are very basic units but handy for am radio checking!

@retro_tech Жыл бұрын

Indeed. Thanks for the suggestions.

@andybbeck2043 Жыл бұрын

super channel 👏

@retro_tech Жыл бұрын

Thanks!

@FloydAtema 5 ай бұрын

Cool channel, instant sub!

@retro_tech 5 ай бұрын

Thanks!

@Donno308 Жыл бұрын

Hi Kristof I found this video very interesting. I have a very similar signal generator- mine is model LSG 11. It s essentially the same as yours except for the modulation you have a choice of 400Hz, 1000Hz or Crystal and it has a socket to insert a crystal. This is my only signal generator and it works quite well for AM alignments and signal tracing. If I keep on restoring FM radios I guess I’ll have to buy a modern sig gen but they’re not cheap! I do have a frequency counter to check it with (you might have seen it in my videos) but I have found the scale on the old Leader LSG 11 is dead accurate! After watching this I will definitely replace those “death caps”. I recently gave your channel a bit of a plug on some Facebook vintage radio groups. I hope you don’t mind. Maybe it will help things along a little. All the best

@retro_tech Жыл бұрын

Yes, I already noticed the signal generator in your videos. For AM alignments it's indeed very usable. For FM, not so much. I also don't have an FM RF signal generator since they are quite expensive. But you can also use a cheap FM transmitter to get the FM pretty close. Thanks for advertising my channel!

@stellolaorga7166 Жыл бұрын

hola tengo el mismo y funcionado.

@InssiAjaton Жыл бұрын

How about dirty switch contacts. You started playing and the contacts cleaned by repeated wiping action. On the other hand, one capacitor +tolerance and the other - and quite soon you are out of the oscillation condition. To get anything near sine wave, the feedback has to stay close to the critical gain, that is at the amount where the oscillation just started. Another issue is your output signal jitter. I would speculate it is related to your lower anode voltage. And regarding tothat, you probably have extra ripple on the DC, due to you likely operating at 50 Hz rather than the American 60 Hz. Having the single wave rectification and selenium diode both contribute. Silicon diodes have less than 1 V drop. A 250 V rated selenium stack may have well over 15 V drop.

@retro_tech Жыл бұрын

Thanks for the suggestions! It's definitely not dirty switch contacts, though, as the oscillation started working when I bridged one of the capacitors with a new one.

@kriegsmarinesammler9328 Жыл бұрын

Ik heb vandaag net een Model 11 opgehaald, belangerijkste Capacitors zijn goed nagekeken en uitgetest. Hij blijkt alles te doen, behalve zijn Ton/signaal/frequenz maakt hij niet. External input/sound ontvangt mn Telefunken Ela 1012 wel, moet ik nog eens verder onderzoeken. (The scale frequency on my LSG11 is not as accurate tho.)

@retro_tech Жыл бұрын

Veel succes!