Solid state substitution for 215A triode Peanut Tube

[W1TAV]

I have a Northern Electric R11 receiver  and R15 amplifier given to me this last weekend. Interesting bit of history in regards to the 1920's miniature tubes.   Before I go off reinventing the wheel, looking for tips and the efforts others in substituting SS Devices for this little triode.  I am by no means looking to hack this set, just thinking of a drop in or behind the cover clip lead connected substitution. (a la WA1QIX  )

[WA1GFZ]

what is the plate voltage? Do you know the operating plate current?
IRF610 if you can tolerate 135 pf input c
IRF510 lower voltage rating and may have less c

You can solder it across the tube socket. small resistor in series with source and will need a little positive bias on the gate

[Rob K2CU]

The 215A is a low power device. See: http://tubedata.tigahost.com/tubedata/sheets/136/2/215A.pdf for a datasheet.
The 215A has mu and transconductance (mhos) are on the order of 1/10th that of most J-FETs, devices most similar to triodes.
There is probably no direct substitution SS part to wire into either a tube base or across the socket. It might be possible to build up a circuit to mimic the characteristics of this tube. You might find better results by trying out one of the Russian rod tubes, connected as a triode. See: http://www.radiomuseum.org/forum/russian_subminiature_tubes.html and also: http://www.techtir.ie/blogs/watty/miniature_valves_2.


You can usually find these parts in lots of 10 or 20 on Ebay for about $1 -$2 per part. They might do the trick for you as they are also extremely low power with similar characteristics to the 215A. Since there are detailed curves available for the 215A at the above website, you should be able to figure a match up. I have purchased some of the 1zh24B and 1p24B parts to experiment with. Got them through Ebay and it only to a week to get the packages from Bulgaria and Odessa. Apparently the Russians were building loads of these parts through the 90's and using them in military equipment (EMP proof).

[k4kyv]

Why would you want to run a solid state replacement in a 1920s receiver?  If the original tubes are not available, you could build an adaptor socket and replace the tube with one of the miniature tubes designed to run portable battery sets, before the advent of transistor radios.  Those tubes have 1.5v filaments and  run with plate voltage as low as 45 volts.  It should be easy to find a triode with a pair of diodes inside, designed for the detector/1st audio stage.  Just ignore the diodes and run the triode section.  It would probably have higher gain than the original, but if self oscillation is a problem, insert a loss resistor in the plate or grid circuit to cut back the gain to the point of where it no longer oscillates. There would be no need to make any changes to the receiver itself, but you might have to use a different filament voltage (A battery).

I have heard of the 6C4 being used to replace 01-As, and type 30 tubes used to replace UX-199s.  I think I read somewhere that one of those little squatty miniature triodes with the pins coming out the sides (used around the time of WW2 for receivers in the UHF range) makes a good replacement as well.

Also, some of the sub-miniature tubes might work, if you have any lying around.  They commonly show up at hamfests, although tube data on these may be a  little hard to find. They didn't stay around very long, because solid state started to become practical about the time they were first released.

[w1vtp]

Steve

This might take a little detective work.  Take a look at this site. Raytheon in her tube heyday made a pretty good selection of "pencil tubes." Here's a web page with characteristics of some of them

http://pw2.netcom.com/~wa2ise/radios/penciltubes.html

As Don suggested using a tube instead of a SS device would be be the preferred approach.  Heck, There is a Raytheon substitution for the very expensive WD 11 tube that goes in my Radiola III (see  http://www.dialcover.com/tubes.html ).  Good luck with the search

Al

[W7TFO]

The WECo 215A was in production for over 50 years, you ought to be able to find a couple from some of the better tube gurus.

Here is what the man says below...

73DG

[W1TAV]

Thanks for all the good ideas!

Don, "Why Solid State"  You are correct with your thoughts. It is no different then when someone says to me they what to put electronic ignition in a Model T (yes they do make such a device) My first thought was the 215A was going to be unattainable. (at least at a reasonable cost) Given the restriction of the front panel socket, my thoughts were for a SS solution behind the scenes so to speak and putting a Dud 215A in for display.  

Thanks for the ideas of finding other 1V filament tubes from later portables.  It is very interesting that the US Navy was still employing the 215A in the 1970's!  

I was given the R11 and 2 R15's along with a Cat's Whisker.  

[k4kyv]

I suppose it's the difference between restoring a piece of "vintage" equipment actually put to routine use, versus one (perhaps "antique" would be a better word than "vintage") restored as a working museum piece.

I would place the Model T in the latter category along with the R11, whereas one might actually drive a restored 1935 sedan to work occasionally or even regularly, and use a pre-WW2 HRO with silver dial as a station receiver.

Therefore, I wouldn't convert the Model T to electronic ignition nor convert a R11 to solid state, but I might consider adding electronic ignition to the 1935 Chevrolet (without throwing away the old hardware), if I planned to drive it regularly, and make a few (fully reversible) modifications to the HRO to improve its performance if I planned to use it as the main station receiver.

I jury-rigged an outboard box of selectable mechanical filters in the pre-war HRO I used until I acquired the 75A4, but it didn't require drilling any holes and only required a couple of solder joints to the AVC line, and after I removed it, no-one could tell that such a modification had ever been installed.

Then there are the purists who insist that everything be completely original.  For example, even bolts that are completely hidden under the engine block of the Model T must have the proper style of head stamped with the proper markings (or lack thereof), and waxed capacitors hidden beneath the chassis of the HRO must be restuffed with a modern one to look original, rather than just throwing in an Orange Drop.

I probably wouldn't go to that full extreme (who's going to see the bolt in the Model T anyway, since it will remain hidden until next time the engine is pulled?), but it is disappointing to look under the chassis of a 1928 radio and see a bunch of orange drops staring you in the face.

I would look for an appropriate 1.5v 7-pin miniature triode as a temporary replacement and make up an adaptor socket, while keeping an eye out for a real 215A or something nearly identical. Look in the RCA Receiving Tube manual to find a suitable replacement type, and look up Antique Electronic Supply www.tubesandmore.com/ or one of the other well-known tube vendors to see if they have any in stock.

[KE6DF]

There are ads for 215a on epay.

http://www.ebay.com/itm/Pair-Northern-Western-Electric-215A-Radio-Tubes-Good-/150767702055?pt=Vintage_Electronics_R2&hash=item231a749027

[The Slab Bacon]

that thing looks just like a '99. I wonder if that was WE's equivelant to a '99??
Even if it isn't a '99 could prolly easily be made to work.

[KM1H]

There were lots of US submini tubes from the WW2 era to 80's and many are easy to find. Many work fine at 22-45V.

Also availble are the 12VDC space charge tubes in early 60's hybrid auto radios, those are almost free.

I used FET's in place of 01A's the very few times I actually cared to use one those archaic radios decades ago.

Carl

[k4kyv]

that thing looks just like a '99. I wonder if that was WE's equivelant to a '99??
Even if it isn't a '99 could prolly easily be made to work.

I think they are smaller than a '99, more like the size of a 6C4 or 6AQ5.

That reminds me. I recall years ago as a kid ruining a good WX-12 that I picked up in an antique shop in New Orleans.  It had a pretty raised-letter "Songbird" paper label glued to the envelope, and marked as type "X-12".  I was a little familiar with the numbering system, and knew that that the last two digits usually were the significant figures in the old numbered tube types.  For example, an early '80 rectifier might be labelled as a UX-280, CX-380 or something similar.  So I figured this must be a really early version of the type '12A tube, which takes 5.0 volts on the filament.  I hooked it up to a 6-volt lantern battery and poof went the filament! Turns out the WX-12 takes something like 1.1 volts.

[W1TAV]

Well I looks like the Raytheon 5676 Pencil Tube is a good Substitute without going Solid State or at $4.00 or so, not breaking the bank.  With a little bit of effort, it could be made to work in the same space as the peanut tube that at a glance would look about right.  As I have been looking around at radios of this vintage, it appears the the two amplifier units were indeed meant to be hooked together as a 2 stage amp. I see that Northern marketed this configuration in a later offering.  I have several other 1920's radios, however this is the 1st one I have ever wanted to bring back to life.
Don, I believe in keeping things stock or at least vintage, thanks for pulling me back from the Dark (no glow) side..