27 March 2021

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.


23 March 2021

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.

One tube CW transmitter (tentative)

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!

18 March 2021

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!



08 March 2021

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?