Help with unknown vacuum tube / valve

In the assortment of vacuum tubes I bought there are few items that look all the same and all without marking. What is worse is that they do not look like any of the almost 40 kinds of tubes that do have a marking!

So I ask my readers for help to give a name to these B9A/noval tubes. All nine pins are connected. There are two identical sections and filament runs happy at 6.3V. The anode/plate is probably connected to pin 9.

Is it a double triode? A double pentode?

Please suggest your answer in the comments or via email to ik1zyw at yahoo.com. Thanks!
 

"Side" view.

"Front" view.

 

Things got out of control with the all-valve TX project

The more I read about valve (vacuum tube) oscillators and transmitters, the more I understand the inner workings of those relatively simple circuits. Once I realised that a triode-heptode or triode-pentode tube can work both as oscillator and "PA", I concentrated my efforts around a PCL-805. Until my own hands presented me the nest shown in the picture.

Alright. I will take one step back and beam my first venture into the world of vacuum tubes towards two separate stages: the crystal oscillator and the power amplifier. I do have enough tubes and sockets. What I am missing is a decent assortment of high voltage capacitors and high wattage resistors! Let alone RFC!

Valve sockets!

Now that I got a hundred vacuum tubes and an idea of a project, I needed some matching sockets. Without in-person flea markets, I turned to eBay and with a bit of luck I spotted a lot of assorted used sockets that nobody wanted. I think I got about 100 pieces, which makes it 0.15€ each once shipping is taken into account. Of course I will never need all of them so I probably ended up overpaying just one socket :)

Besides lots of octal, loctal and noval sockets in different shapes, there were few interesting items, proof of a time when electronics were booming and everyone tried to impose their standard (or a technological lock-in).

I've collected them for a group picture (I forgot the ubiquitous *octal).

Numbers represent the # of contact points.

Needless to say that I have no tubes that fit most of these, and some tubes that have no matching socket.

If anyone wishes to give them a name, please do so in the Comments!

 

 

EF80, EF183, EF184 XTAL oscillator

(This post has been deleted by Blogger because someone flagged it as malicious. No idea why. Then they changed their mind and returned the post in Draft state.)

While passing through forgotten boxes of forgotten components looking for some interesting TTL/CMOS ICs for an artistic project, I found two large XTALs for 2.0971 MHz. I think they were meant for some valve circuit, so I looked for an oscillator circuit with one of the tubes I have most: EF80.

Using the DIY B9A base I rigged together the most promising circuit I found online of a CW TX, with resistors "close enough" to quoted values. The ugly result is shown in the picture as well as the circuit diagram.

Diagram and test circuit.

 

I fed 6Vdc to the filament and 150V HT and it did oscillate. Cool. Time for experiments.

I could reduce filament to 5V at 300mA and everything was fine.

I could reduce the HT to 30V and it didn't stop oscillating, alas the signal picked up by the nearby receiver was much weaker. I couldn't go with a lower HT with today test setup.

Then, while I was at it, I tested all EF80 valves I had already separated from the rest. Not happy with the result, I checked through the list and found out that EF183 and EF184 pentodes are pin-compatible with EF80, so they got tested too. I could even re-stamp a few tubes that had become anonymous.

The result of a couple of hours of fiddling with on/off switched of power supplies is that I have 28 working pentodes waiting to be used in a real transmitter.

Now: VFO or XTAL?

Checking a static discharge trick with the NanoVNA at UHF

Today I received a question about a post from 8 years ago: how to tame the static build-up in a GP or collinear antenna. Back then I had done some research and concluded that a high value non-inductive resistor could be used, especially at low TX power or RX only.

Now that I own a NanoVNA I can confirm that the impedance is not affected. I quickly reused the LoRA antenna from last Summer, which turned out to be resonating at 750 MHz (if we trust the NanoVNA). This is the curve on a 300 MHz span (well, it stops at 900 MHz on the right):

Just the "open" GP antenna.

 

Then I added a 10 kohm 1/4W resistor across radiator and radials and the result is almost identical (the marker has moved):

After adding the 10kR across. See next picture.

The very (quick && dirty) antenna under test.

So, if we trust the NanoVNA at the upper limit of its working range, this trick does not compromise the impedance. I might also have been lucky on the single experiment I've made, so do your measurements first.

Sorting a box of vacuum tubes

So, there comes the time you become the owner of a shoebox full of almost-no-value one-hundredish vacuum tubes and you need to sort them out. I do want to use (some of) them, not immediately. I also have no facilities to keep them sorted in a logical way, so I had to do it efficiently.

First of all I separated the magic eyes, since they can be easily recognised and tested.

Then ... I simply transferred the tubes one-by-one from one box to another and typed the part number in a spreadsheet, when still visible. Those tubes without a usable marking have been compared physically & visually to others and some got a supposed part number with a marker pen. A dozen were left anonymous, separated from the rest, for other projects.

Once all the names are in a spreadsheet just create a pivot table to see how many different types you've got, and how many each.

Now go back online and look for projects with those tubes :)

Freeform two transistor LED blinker completed

My first freeform electronics sculpture is finished! Visually it is a replica of Mohit's work with a change in the diagram (one resistor less). The LED blinks approx once every second, and blinks become more frequent as the available voltage decreases towards LED's forward voltage.

The 1uF capacitor that sets the frequency is charged though the leakage current passing through the LED. In ultrabright clear-case LEDs you see a faint emission in this phase (dark room implied). Then you are blinded by the following pulse :)

I also added a 1F 5.5V supercapacitor that keep the blinker running for more than 12 hours with a white LED. If a red LED is used, it lasts 24 hours.

If a solar panel is added in parallel to this circuit to top up the supercap during daylight (add a diode to prevent discharge back to the panel), basically it lasts forever.

The stand-by current is fractions of microamperes [uA] and the average lies around 30 uA (calculated). Not easy to measure, huh!

The hardest parts are to get straight wires and component leads and to keep everything in place when soldering when both your hands are needed to hold the iron and the solder. Then you need to make clean solder joints.

While is may seem a useless exercise, freeform electronics forces you to think out of the box even if you are reproducing someone else's work. Give it a try.

PS: working circuits impress 10x fold the audience.

Freeform two transistor LED blinker

Intermediate result.

As announced, I wanted to try Freeform Electronics Art. My last PCB designs for clocks were meant to be artistic so that they could be displayed to the public even without a case. Freeform Electronics uses no PCB: it's all self-standing and built "in the air".

I chose to replicate Mohit Bhoite's two-transistor LED flasher because of its simplicity and I had all parts already at home.

I deliberately chose to ignore some of his planning and construction techniques (shared in videos featuring him and his art) so that I would learn more of and during the process. Moreover this blinker is very simple, forgiving and lightweight and almost any building technique should work.

Another view, next to an SD/TF card for size comparison.

Pictures show an intermediate result with 2N5401, BC347C and three resistors. I am half-way to the end, component-count-wise.