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Mimic a Type 80 rectifier tube

Eric Wells

Aug 9, 2017
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Hello all. I'm slightly better than a newbie with electronics, as in I know how to read diagrams & assemble circuits. I have inherited an antique radio which I'd like to replace the old tubes with modern, energy efficient electronics. There are 4 different types of tubes, but the first I'd like to work with is the rectifier.

The type 80 rectifier is a half-wave rectifier with 650V 36mA AC input and 5V DC output. In addition to that I'd also like to include a bulb/LED of some sort to maintain that nostalgic orange glow the tube gives off when it's powered up.

Thank you
 

Tha fios agaibh

Aug 11, 2014
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Many are of the opinion that you get a warmer richer tone from tubes.
Why not just leave it as-is or restore it to its original glory? I get a kick out of the slow warning up of the tubes before music kicks-in.

I suspect you'll have to replace more than just the tubes if you want to transistorize this radio. Easier to just build from scratch.
 

Eric Wells

Aug 9, 2017
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I agree with that. My idea is to put the electronics into the tube packages and plug them into the original sockets. If, for whatever reason I want to put the original tubes back in, the radio would work just the same.

The tubes get incredibly hot, I'm hoping to make this radio a bit more energy efficient too.
 

Tha fios agaibh

Aug 11, 2014
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It sounds like it could get complicated trying to match the characteristics of the tubes let alone make it more efficient using existing components.

Cool idea, but I don't know if it's feasible.
 

Eric Wells

Aug 9, 2017
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Like I said, I'm a bit of a newbie. What kind of characteristics would be difficult to match?
 

Tha fios agaibh

Aug 11, 2014
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If you look at a data sheet for the tubes you are trying to replace it will tell you specific requirements of how they operate.
Similarly for transistors they have data sheet telling you their specs. Trying to get a transistor (or circuitry) to match the tube specs sounds like a daunting task.

You may be better off disabling original radio and building a transistor radio circuit and just tap into the original on/off volume control knob, speaker and tuning linkage?
 

kellys_eye

Jun 25, 2010
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Good luck trying to emulate a tube using solid-state electronics! Many have tried (unsuccessfully) other than for some 'basic' tube versions such as the triode. The FET is as close as you can get to a basic tube for performance.

But it isn't as simple as swapping out tubes - you will have to match the biasing requirements and impedances etc. To 'change' the tube radio to a solid-state one will mean considerable reworking of the schematic to the point of 'why bother'.

Some of the basic devices, such as the half-wave rectifier tube you refer to, can be swapped for two small diodes quite easily though. It's a common swap for those who aren't particular about originality.

There is a huge vintage radio preservation collective across the internet and the pleasure of restoring a vintage valve set cannot be under-estimated. Some sets are particularly collectable and VALUABLE for the fact.... what model do you have?
 

duke37

Jan 9, 2011
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According to my valve book the type 80 rectifier is full wave capable of 350-0-350V at 125mA.
This does not agree with your specification.
The output could be 350*1.414 = 500V, not 5V
The heater takes 2A at 5V so a dissipation of 10W. As said this valve can be replaced with a couple of diodes eliminating the heater.
The power consumed by the rest of the set will not decrease unless you reduce the voltage and replace the valves with solid state devices. It would be more realistic to get a transistor set to refurbish. I have a LW/MW seven transistor radio which on low volume runs on 9V at about 10mA so a power of 90mW. I doubt if you could do better than this.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Another issue is that the tube will have a higher voltage drop than silicon diodes. This will generally lead to a higher HT which may be a problem for the other valves.
 

73's de Edd

Aug 21, 2015
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Second request . . . What is the brand and model number of the set.
If it was 4 tubes . . .including the rectifier . . . it certainly wasn't much of a set to begin with.
 

Eric Wells

Aug 9, 2017
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Sorry for the response delay.

The brand & model number of the radio set is a Philco model 20.

Here's a link to the pdf with the socket readings, diagrams, chassis images, etc: http://www.nostalgiaair.org/PagesByModel/582/M0029582.pdf

Here's a quick image of the schematic:

Model%2020%20circuit%20diagram.gif

Model%2020%20circuit%20diagram.gif
 

Irv

Jun 7, 2017
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First of all, with old tube-type sets like this, even if you had all the tubes, brand new, chances are you would have to replace nearly all of the capacitors and some of the resistors. Those things break down due to age, heat and voltage. Replacing "just" the tubes with transistor circuitry wouldn't fix those parts. Secondly designing transistorized circuitry to "replace" the tubes and still use the existing (repaired) other parts would be a job for a highly skilled engineer (let's say tens of thousands of dollars worth of work). Still want to do that?
 

Eric Wells

Aug 9, 2017
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First of all, with old tube-type sets like this, even if you had all the tubes, brand new, chances are you would have to replace nearly all of the capacitors and some of the resistors. Those things break down due to age, heat and voltage. Replacing "just" the tubes with transistor circuitry wouldn't fix those parts. Secondly designing transistorized circuitry to "replace" the tubes and still use the existing (repaired) other parts would be a job for a highly skilled engineer (let's say tens of thousands of dollars worth of work). Still want to do that?

Yup, new capacitors are on their way and will be replaced next week. The radio is really working well in its current state, even with the old capacitors & tubes. I think the radio was well taken care of because some of the tubes were tested and installed in the 70's & the 80's.

Hmm, spend tens of thousands of dollars on this project... Tempting :/
 

Terry01

Jul 5, 2017
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I take it this is a very old set well worth bringing back to life? I love seeing old things brought back. Something well cool about old stuff. Good luck buddy,hope it turns out real nice for you.
 

Eric Wells

Aug 9, 2017
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I take it this is a very old set well worth bringing back to life? I love seeing old things brought back. Something well cool about old stuff. Good luck buddy,hope it turns out real nice for you.

Thank you. I'm in the middle of restoring it and am replacing some old, out of spec resistors & capacitors. I'm really looking forward to bringing it back to life.

What's neat is that I found a place in the circuitry which would allow me to attach an AUX audio input like a computer or a smartphone. I made a short video of the results:
 

Terry01

Jul 5, 2017
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Ha nice! I'm still very new with electronics but loving getting stuck in! There is so much to learn about so many things going off in so many directions!
Do you think when this was first made they would have thought someone would be plugging a smart phone into it nearly 100 years later? Like you say "WELL COOL"!
 
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