Saturday, April 25, 2020

6Ж5Б-В (6J5B-V) Audio amplifier

Do not expect to have here the latest greatest audio tube/valve amplifier.

Having said that, it works for me and still give a reasonable audio output, understand by reasonable; it's audible but not big volume, you can keep comfortable the speaker 10cm from you ear. Let's said this is the amplifier you need in case you run out of any other device that can give you audio amplification.

Some photos and diagram bellow.

The glow:

..violet color on the heather is due to camera, in reality is more on the orange/yellow side.

The testing board

The schematic

 ..this worked for me, for sure there could be a lot of improvement but I just wanted to try and prove the concept. The "audio output transformer" is just a 230/9V power supply one, I tested with a 230/15 and with one with multi taps and all work but would be preferable to use a real audio one.
This also works if you remove the left side o the circuit and inject audio directly on pin 7 of the rightmost tube (with the audio transformer), at the expense of lower output.

Audio sample listening to 10.100Mhz weather station with a lot of fade.

The audio from the capture is not the greatest, a little better in real but still on the low side, I'm sure with a real audio output transformer, a higher supply voltage and some optimization would be a reasonable amplifier, but again you have other specific tubes and designs to make it better. 

Have fun!

Saturday, April 18, 2020

World Amateur Radio Day - 6Ж5Б-В (6J5B-V) Oscilator

Yes, it is today at least for those interested in calendar advents!

I suspect that for the majority it will be all days, weekends or occasionally, it does not matter as long as the spirit is alive. I also does not matter if your interest is DX, QSL collection, home-brew, 500m or light-wave.

For me since it's mostly building and learning RF electronics in the process, here's today "project":

I had some Russian 6Ж5Б-В (6J5B-V ) miniature tubes laying around for long time, so decided to build something with them, or at least try.
I think they were chosen just for fun and to make combined postage in another components order.

Components values are not optimal since I was building and doing guess work at the same time trying different values. Keep in mind I'm no expert in tube technology (nor transistor for that matter just to be clear).  That said, do not replicate for any other purpose than fun.

The tube/valve 6Ж5Б-В (6J5B-V ):

The warm glow, always nice to see:

and the outcome:

No output filter but again the RFC used are on the low side values:

Final schematic:

(add: latter changed the top 200pF capacitor for a 20PF)

To be honest I was not expecting it to work since the anode voltage was too low and I haven't a higher voltage power supply.

Have a great day!

Sunday, April 12, 2020


Previous post was about a home made and cheap solution to provide instrument control via GPIB.

This time a less cheaper alternative but still in budget.

Since the prices of a proper PCI GPIB board or a PCMIA version are on high values I searched for older cards, you have plenty of less expensive ones but they are for older PCI or even ISA interfaces, I managed to get one National Instruments PCI 32 GPIB board for the sum of 30 EUR (inc shipping) but I didn't had the computer for it! (currently only have the laptop with me), again on the used marked got an HP8200 Elite PC with OK specs for 62 Eur delivered. The total of my setup is then 92 Eur, that is lower value than what people ask for a PCMCIA and some PCI GPIB cards, adding to the lower value I have now a new PC for the lab.

I wanted a small form computer due to space limitation, the drawback is; it does not have full height slots, so, had to add and extension cable from the slot to the card drill a bit on the back panel and place the board zip tied inside. Since the PC is not suppose to move around, this setup will work.

Here's the result:

 Not the prettiest of the hacks but very few metal tools available currently so all mostly done with pliers.
The board in place horizontally still without the PCI cable extension attached.
 The PCI extension cable:

Since I use Linux, had to load the driver and after some "fighting" manage to get everything working.
The "lspci" confirming the card is in place.


And the driver:
       gpib_common            45056  2 tnt4882,nec7210

and loading messages:

[   13.495862] gpib_common: loading out-of-tree module taints kernel.
[   13.505196] gpib_common: module verification failed: signature and/or required key missing - tainting kernel
[   13.505484] Linux-GPIB 4.3.0 Driver
[   13.506402] gpib: registered ni_isa interface
[   13.506403] gpib: registered ni_isa_accel interface
[   13.506403] gpib: registered ni_nat4882_isa interface
[   13.506404] gpib: registered ni_nat4882_isa_accel interface
[   13.506405] gpib: registered ni_nec_isa interface
[   13.506405] gpib: registered ni_nec_isa_accel interface
[   13.506405] gpib: registered ni_pci interface
[   13.506406] gpib: registered ni_pci_accel interface

Using this card, already manage to program some simple code for all of my instruments, except the EIP 371 frequency counter that was not tested yet.

In the future I plan to create some posts with code examples for the following instruments:

Marconi 6960A Power meter
HP 3478A Multimeter
HP 5316B Frequency meter
ICS 4896 GPIB to quad Serial "converter" (this is not a serial do GPIB converter so can't be used to control GPIB instruments)
HP/Agilent 6621A power supply
R&S NRVS power meter

Have a nice day!