Help about 5R4 rectifier

[Miguel Lopez]

Hello

I have a 5R4 tube which supposely should be a rectifier, but I have some doubts about it.

All the pictures that I have seen on the web of the 5R4 diode shows a glass envelopo device, like the one shown in the pictures bellow, but the one I have is a metal envelope device which looks exactly as the 5T4 in the pictures bellow, so what this tube is? Help please.

https://www.radiomuseum.org/tubes/tube_5r4.html
https://www.tubeworld.com/5r4.htm
http://www.r-type.org/exhib/aaa0145.htm

[ms660]

It's not a solid state replacement is it?

Lawrence.

[Miguel Lopez]

I hope it isn't. AFAIK, it's a full wave vacuum rectifier. Sorry, I have not test it yet.

[ms660]

The only other picture I've come across on the web is a 5R4GYM by International Servicemaster.

Lawrence.

[Station X]

As far as I know the solid state replacement for the 5R4 was designated 1N1239.

I believe it had a metal can similar to that shown, but some versions used short cans.

A test with a meter would soon show if it's a solid state version.

https://www.radiomuseum.org/tubes/tube_1n1239.html

[Station X]

Lawrence's 5R4GYM looks much more likely.

[Miguel Lopez]

Thank you guys.

I'll make the test today and I will let you know tomorrow.

Thanks

[Radio Wrangler]

Originally Posted by Miguel Lopez

Hello

I have a 5R4 tube which supposely should be a rectifier, but I have some doubts about it.

All the pictures that I have seen on the web of the 5R4 diode shows a glass envelopo device, like the one shown in the pictures bellow, but the one I have is a metal envelope device which looks exactly as the 5T4 in the pictures bellow, so what this tube is? Help please.

https://www.radiomuseum.org/tubes/tube_5r4.html
https://www.tubeworld.com/5r4.htm
http://www.r-type.org/exhib/aaa0145.htm

Hi Miguel.

The original 5R4 at the time of its introduction was one of RCAs series of metal-cased tubes and it's quite common to find one all in black-painted metal, with American military markings from the WW2 era. It's one of the larger of the metal valves.

The 5R4G and GY are the same rating of rectifier, but in a 'shouldered' glass envelope. These seem to be the most common 5R4 variant. The glass bottle is cemented onto a normal international-octal base.

The first picture you've linked to shows a variant with a base that extends up around the glass. I've never seen one like this before.

The 5R4 is a tough and reliable valve.

David

[turretslug]

That extended base is an anti-creepage type, intended to mate with a deeply-recessed socket- the 5R4 has an unusually high PIV for an IO rectifier and it was apparently found that flashover between tags and the metallic securing ring could occur under some circumstances of high humidity and/or low atmospheric pressure, hence the "W" professional/military style with revised base. That type of presentation is quite common on surplus market types, seemingly made by Chatham, but the matching recessed socket is much rarer and more difficult to find. I first encountered it in a slightly fearsome "audiophile" amp using 211 output valves with around 1100V HT, that high PIV means that they are in demand for this sort of full-wave application.

[ms660]

I can't find a 5R4 (metal) in the RCA tube manuals (receiving or transmitting) unless I've missed it.

Anyone find the data for the original metal one or a picture?

Lawrence.

[Station X]

Picture here?

https://tubeworldexpress.com/collect...9-40-and-50-40

[ms660]

Originally Posted by Station X

Picture here?

https://tubeworldexpress.com/collect...9-40-and-50-40

That's the servicemaster one I referred to earlier, I still haven't found anything on an original RCA 5R4 metal valve, no pic, no data, maybe I'm having a bad search day.

Lawrence.

[Station X]

I think we need a picture of Miguel's actual valve.

[Miguel Lopez]

Well, it is defitively a vacuum diode

I tested the two diodes with the ohmeter and found infinite impedance between any pair of diodes leads (which is expevted on a vacuum diode). Then I measured between pins 2 and 8 and I had a reading of 2,13 ohms which is very close to the datasheet specifications if we have into account that the filament was cold. (well, I had connected it before to 5 VAC to see if there was a contact spark but it was just a few seconds)

I did not connected it to a test circuit but I guess that it definitively must be a vacuum diode and not an SS replacement, which makes me very happy.

Originally Posted by Station X

I think we need a picture of Miguel's actual valve.

I promise to show one picture tomorrow

[Miguel Lopez]

A promise is a promise. Here is the picture.

Yesterday I did the final test. I connected it as it should be an SS replacement with a center-tapped transformer and a load. I had no output

Then I powered the filament with 5 V and almost inmediately I had output, so I have to conclude that it is a vacuum diode and not an SS replacement.

[Radio Wrangler]

It's directly heated, so there is no thermal lag of having to warm up a cathode. 5R4s come up quickly. In the glass versions you can see the filaments are coated ribbon.

That's a real 5R4!

David