PDA

View Full Version : OT Need help to ID this tube



yf
05-31-2012, 05:41 AM
I was given this tube by an old time electrician who is unfortunately long gone.
I vaguely remember that he said it was used in some type of radio transmission apparatus.
I clearly remember he said it had cost many thousands of dollars new.
I wish I had asked him for more info back then (about 18 years ago).
I've been cleaning up and came across this and don't know anything about it.
For size reference, in the top pic, its sitting on 5/4 x6" lumber.
It weighs about 8 pounds.
I'm assuming he put the hose clamp on to protect the heat sink fins, which appear to be copper or high red brass.

TIA :-)

http://img.photobucket.com/albums/0603/machines/IMG_20120530_182604.jpg

http://img.photobucket.com/albums/0603/machines/IMG_20120530_182742.jpg

http://img.photobucket.com/albums/0603/machines/IMG_20120530_182759.jpg

http://img.photobucket.com/albums/0603/machines/IMG_20120530_182626.jpg

fredf
05-31-2012, 05:50 AM
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CFMQFjAA&url=http%3A%2F%2Fwww.rfeworld.com%2Fdatasheets%2F7 237A.pdf&ei=ly_HT9C-Ms_46QHPyOm_Dg&usg=AFQjCNE2Tp0QocTtPGWkatGpwuoBdzltrA&sig2=PVeJf97o9R1Ip6DTapotMg

yf
05-31-2012, 05:54 AM
I did find this.

http://www.rfeworld.com/datasheets/7237A.pdf

However aside from knowing its a triode I don't understand much of this data sheet.

Apparently this link is the same as the one posted above by fredf.

Stuart Br
05-31-2012, 08:27 AM
That's a Monster - 10kW at 30MHz or 6kW at 50MHz, boy that would hurt...

J Tiers
05-31-2012, 09:19 AM
The power and operation figures are mostly for 2 tubes in push-pull, so not *quite* as large....

But the tubes are clearly for medium power usage among transmitter tubes.

Note the driving power of 430 watts, 0.6 amps grid current... That's the power needed at the INPUT to get the listed output power...... you need a very substantial amplifier just to DRIVE the tube to those outputs

KIMFAB
05-31-2012, 10:38 AM
That looks very much like one of the output tubes used in the 10 Kw transmitters we had at the Naval transmitting site that I was stationed at in the late 60's.

Didn't get any pics unfortunately, being military and all.

I do, however, have a 1 Kw AM transmitter out back that would probably work as a driver for it. Probably could cut you a deal. :D

browne92
05-31-2012, 10:52 AM
If it was used in a push-pull configuration, those were usually changed out in pairs. If one died, you changed them both. That may be the survivor. Also, I don't know if that one falls into this category, but I seem to remember that larger tubes could be sent off and rebuilt.

Stirring up some memories now...

Forestgnome
05-31-2012, 01:00 PM
That looks very much like one of the output tubes used in the 10 Kw transmitters we had at the Naval transmitting site that I was stationed at in the late 60's.

Didn't get any pics unfortunately, being military and all.

I do, however, have a 1 Kw AM transmitter out back that would probably work as a driver for it. Probably could cut you a deal. :D
Small world. I was also at a couple of NavRadTransFac's. Dixon and Deep Freeze. Worked on the AN/FRT-39's, 40's, 72's, and 84's. For those not familiar these are 10kw-100kw HF transmitters. That tube is very similar to what we used, but the ones we used had ring electrodes at the bottom instead of pins. Typically the contacts and fins were silver-plated copper. Also there was usually beryllium in the ceramic so disposal was controlled. I believe the exciter section on the FRT's were 1kw.

yf
05-31-2012, 01:45 PM
First of all thank you to all who replied.
The replies raised more questions.

How can I test this?
If good, can I sell it?
If not, does it have any scrap value, or
should I make it into a table lamp? :-)

I still don't understand the data sheet, but I now know its a
transmitter.

Thanks for the responses.

darryl
05-31-2012, 04:47 PM
I have a few similar tubes, though not quite as large or powerful as that one. I was definitely thinking of the table lamp idea. I would power up the filament of course, which would make it into a heater. With some type of ornate grid suspended above, it would become a place to keep your coffee cup warm :)

Forestgnome
05-31-2012, 05:18 PM
About the only test you could do would be to use an ohmmeter and measure the filament resistance. Otherwise you need to be able to bias it to measure conductance which probably isn't feasible. It won't tell you that the tube is good, but will tell you that the filament should work. This is going back a ways, but if i remember right it should measure between 5-15 ohms. Someone correct me if they know better. The heat sink is the plate and should measure open to any other terminal. One terminal may or may not be connected (shorted) to the filament connections. That would be the cathode. The grid terminal also should be open to any other terminal. Just measure methodically between all combinations of two terminals to find the filaments. By the way, the hose clamp would be to make the plate connection. Generally a strap would slide underneath the clamp.

Forestgnome
05-31-2012, 05:23 PM
I just noticed the link to the datasheet. Filament would be 0.38 ohms.

dp
05-31-2012, 10:45 PM
I just noticed the link to the datasheet. Filament would be 0.38 ohms.

That is the hot resistance at nominal voltage input with 33A of current. Cold, it will look like a short circuit which for most purposes 0.38 Ohms already is :). A quick trip to a car's battery should produce a nice bright yellow glow.

These would have been installed push-pull to reduce harmonics and would have been plate-modulated class C amplifiers, or even class B if derated. They can also be used as modulator tubes for even more powerful systems, but RF is their sweet spot. As class C they could have been used in RTTY and other "digital" modes.

Be cautious of beryllium in the ceramic - assume it is there and treat it accordingly until you know otherwise.

darryl
06-01-2012, 12:01 AM
The data sheet shows a three pin array, with the center and slightly wider pin being a center tap on the filament. The other two pins are then the filament. I believe that since there's so much power involved just in the filament, that those pins would all be used to help draw heat away, either through the socket or through the connecting wires. If you wanted to power it just for laughs, it might be good to also use a method of drawing heat out of those pins- otherwise the glass might crack.

dp
06-01-2012, 12:14 AM
Everything about those tubes including the attachments would have been in the forced air stream. I worked with similarly sized tetrode devices and as I recall the heater/filament circuit would kick in the blowers and the HV needed to have a "thermal invite" before it would be tripped on.

That was the era of cheap energy :)

All the small RF gear I worked on in the 70's went solid state. The last tube transmitter I designed went into production in 1975.

J Tiers
06-01-2012, 12:23 AM
The last tube transmitter I designed went into production in 1975.

The last tube equipment we designed at the old place is still in production........ and they are designing more.:D

MaxHeadRoom
06-01-2012, 12:30 AM
Also resembles the tube in the HF heating equipment I used to install.
IIRC the filament was around 3 kw?
Max.

willmac
06-01-2012, 08:16 AM
Tubes (valves over here) are not dead yet for radio transmitters. The BBC has bought up the last remaining world supply of the tubes they need to keep their 198 kHz service going. This includes the "Test Match Special" coverage which is a ball by ball coverage of international cricket. Since a cricket match like this goes on for up to 5 days and a series lasts up to 5 matches, the service is unique. The Empire will fall and civilisation will end when the last tubes fail and the service goes off air.

See this for full details:

http://www.guardian.co.uk/media/2011/oct/09/bbc-radio4-long-wave-goodbye

browne92
06-01-2012, 11:39 AM
These folks might be interested in it:

http://www.kennetron.com/

If not, I'd stick with the table lamp :)

Lew Hartswick
06-01-2012, 12:23 PM
A quick trip to a car's battery should produce a nice bright yellow glow.
You aren't going to see much of a "glow" with that ceramic envelope.
:-)
...lew...

Forestgnome
06-01-2012, 03:29 PM
That is the hot resistance at nominal voltage input with 33A of current. Cold, it will look like a short circuit which for most purposes 0.38 Ohms already is :). A quick trip to a car's battery should produce a nice bright yellow glow.


True enough.

dp
06-01-2012, 06:34 PM
You aren't going to see much of a "glow" with that ceramic envelope.
:-)
...lew...

Memory may be tricked by my meds but I think there is a glass envelope at the fin section.

Forestgnome
06-02-2012, 11:55 AM
Memory may be tricked by my meds but I think there is a glass envelope at the fin section.
I believe you're correct, however I don't know how visible the glow is as the one's I worked with always had cooling shrouds when operating. Wouldn't want to stick my head in the PA compartment anyway with 10kv bias on!

dp
06-02-2012, 01:58 PM
I know the feeling - I got knocked across the wheel house of a container ship I was working on when I went to discharge the plate voltage of the modulator (thyratron) tube on the 60 kw radar. They have a rod inside the chassis and I managed to get within a blue caterpillar of the plate when reaching for it. That contracts every muscle in your body. I think that was 26kv.

Forestgnome
06-03-2012, 02:19 AM
First day on the job as an ET at the transmitter site, short sleeves, thought I had shut down all circuits. Bare arm in the PA compartment, put a wrench on the screen connection, 1200vdc. Threw me back to the wall. I was done for the day!

yf
06-03-2012, 03:54 AM
Is there any equipment still used that requires this tube?

Paul Alciatore
06-03-2012, 04:12 AM
First of all thank you to all who replied.
The replies raised more questions.

How can I test this?
If good, can I sell it?
If not, does it have any scrap value, or
should I make it into a table lamp? :-)

I still don't understand the data sheet, but I now know its a
transmitter.

Thanks for the responses.

How to test? As said above, check filament for continuity. Check to other connection areas for shorts. Beyond that, the only practical way to test it is in a transmitter designed to use it. Unless it is at full power, with forced air cooling, and being driven by the full power indicated on the data sheet, any other test means nothing beyond what you will see with a $10 Ohm meter.

Can you sell it? Good or bad, you can sell it. But don't expect much. I have maintained many high power transmitters and I would never have used a used tube except in a total emergency. Even at the cheapest station I worked for, I always used new tubes or newly rebuilt tubes from the tube manufacturer and the stingiest owners I worked for never really objected. There was just too much at stake to take a chance on a unknown tube. The tube manufacturers did pay a small amount for returns that could be rebuilt. I doubt that Amperex would be interested in that today, but you could inquire.

It would make a dandy lamp and that has been the fate of many such tubes.

As for the three or four pins conducting heat away from it, probably not or at least not to any great extent. Even though the filament did generate a good amount of heat, the real heat was generated on the plate which is where those fins are attached. If it was operating at an output power of 10 KW then the waste heat was a good fraction of that value, at least 3 or 4 KW and possibly much more. Besides, you wanted the filament to be hot to emit as many electrons as possible. The last thing you wanted to do was cool it. They are large to allow for good conduction even after many hours of hot operation which would encourage the oxidation that is plainly visible on them. The filament was probably the cathode so in addition to the heating current, it probably also had to pass the full plate current. For all that current, they needed to be big. They are probably silver plated and some silver polish should clean them up nicely. The pitting and other discoloration tells me it has probably been used.

BTW, that is a relatively small tube for transmitters. I have used tubes that were about five feet tall and cost tens of thousands of dollars. Try installing a $40,000 tube and have it turn out dead shorted when power is first applied. Not a good feeling. The factory, upon inspecting the returned tube, admitted that they dropped a washer inside it when it was built.

dp
06-03-2012, 12:14 PM
This site might offer some info on the worth of the tube:

http://www.arselectronics.com/ARSWEB/BCpage1.html

Forestgnome
06-04-2012, 10:21 AM
This site might offer some info on the worth of the tube:

http://www.arselectronics.com/ARSWEB/BCpage1.html
Looking at that site reminded me that we used to turn our tubes in to be rebuilt. Might be worth something as a core. Perhaps the company at that link buys cores.

Paul Alciatore
06-04-2012, 01:36 PM
Looking at that site reminded me that we used to turn our tubes in to be rebuilt. Might be worth something as a core. Perhaps the company at that link buys cores.

It is listed there as being available either new or rebuilt. If they rebuild them, they can properly test them.