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Radio Novel rectifier circuit

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Nuvistor
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It’s probably been done before but new to me, this circuit snippet is from PW Oct 1951 and uses a EL91 pentode as a half wave rectifier. The circuit is a 3 valve plus rectifier Midget TRF. Thanks to World radio history web site for the information.

IMG 3102

Frank

 
Posted : 20/03/2024 5:01 pm
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Cathovisor
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You might find some precedent in some early post-war German designs that used the RV12P2000 valve in every stage.

 
Posted : 20/03/2024 11:11 pm
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Nuvistor
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@cathovisor Perhaps where the author got his idea from, he claims it was reliable and had half the heater current of an EY91.

Frank

 
Posted : 21/03/2024 7:33 am
irob2345
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Sorry I wouldn't call it "novel", he's only connecting the pentode as a diode and half-wave rectifying the mains.

He obviously didn't read the data sheet. The EL91 has an absolute max H-K breakdown voltage of 150 volts.

Very unwise usage, since the cathode voltage would exceed 300 volts WRT the heater.

I'd call it "dumb"!

 
Posted : 21/03/2024 9:15 am
Nuvistor
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@irob2345 He used a separate heater winding connecting HK together to circumvent that problem.

Perhaps its just novel to me, I have not seen it before.

Frank

 
Posted : 21/03/2024 10:54 am
Boater Sam
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Grid 3 is of course internally connected to the cathode. Must be a very low power set at anode current is 16mA maximum.

Boater Sam

 
Posted : 21/03/2024 12:25 pm
turretslug
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I'd be a bit concerned about PIV, too. It all shouts "austerity, 1951-style" to me. 

 
Posted : 21/03/2024 12:38 pm
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Nuvistor
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Posted by: @turretslug

It all shouts "austerity, 1951-style" to me. 

There is no doubt about that, however the author claims it was a reliable little set. As per Cathovisors post the Germans were doing very similar things with valves to get radios working.

 

Frank

 
Posted : 21/03/2024 12:56 pm
irob2345
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Posted by: @nuvistor

He used a separate heater winding connecting HK together to circumvent that problem.

Of course! I missed that in my cursory look!

Still dodgy tho....

Mod Note: Fixed incorrect quote

How to correctly and selectively quote someone's post, using the forum appropriate method

 
Posted : 21/03/2024 1:19 pm
Cathovisor
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@turretslug Considering the Korean War was causing huge shortages of nickel (for valve making) and Perspex at the time, this doesn't surprise me one bit.

Here's a set where no less than seven P2000s were used: https://www.radiomuseum.org/r/blaupunkt_5gw646_5_gw_646.html

 
Posted : 21/03/2024 3:29 pm
Nuvistor
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@irob2345 I think it may well have been a ‘needs must’ situation, shortages were common due to having to have most goods for export to help pay the war debt and as Cathovisor states the war in Korea taking materials.

Make do and mend was very common at that time, definitely not a throw away society.

Frank

 
Posted : 21/03/2024 4:52 pm
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