Do you remeber this
lot of six devices which I've picked up on Sunday afternoon?
With this posting I'm going to start a mini series, called
Echoes from a distant past
Part one - The Siemens Rel. send. 22b
Edit:
Part one - The Siemens Rel. send. 22b
Part two - The Two TransformersPart three - The Rohde & Schwarz NGU laboratory power supply unit for vacuum tubesPart four - The Rohde & Schwarz Vacuum Tube Meter URI BN 1050Part five - The Rohde & Schwarz UVN BN 12001 NF MillivoltmeterPart six - The Nordmende digital multimeter DIVO 3355 (with Nixie tubes!)Hello,
I'm starting with the oldest device in this lot (based on the date on the manual: November 1946), the test transmitter Rel. send. 22b from Siemens & Halske (in cooperation with Telefunken). It can generate output frequencies between 80kHz and 28MHz. The output can be modulated (AM) with the internal 400Hz oscillator or modulated from an external source. Output goes from several 10mV down to 8µV.
I haven't switched it on yet because I want to take a closer look at the mains cable and the electrolytic capacitor first.
The device itself is in a very good shape, nearly no rust and the variable capacitor for tuning the output frequency works smoothly.
Let's start with the pictures.
First, the documents which I got with the device.
Please note: the parts list is saying 2x EF12 but the tubes are 2x AC2. The rectifier tube is a RGN354. I'm not sure where those differences are coming from. EF12 is a pentode tube but the tubes being used here are triodes.
![](https://i.imgur.com/Igq5oku.jpg)
Some personal notes of the previous previous owner. I was told, that he was a technician at Radio Bremen.
Translation of the handwritten note:
"Excerpt from the "Handbook of Broadcast Repair Technology". W. Diefenbach, Franke Verlagshandlung Stuttgart. Copyright 1948 - Publisher number 2474"
![](https://i.imgur.com/DdkhE2R.jpg)
Views of the outside with some details. The RF output socket is the same as in old car radios.
![](https://i.imgur.com/9HPnTH5.jpg)
The mains cable and the plug need some closer inspection / repair / cleaning.
The fuse is a 500mA 5x25mm type. While pulling it out I've destroyed it.
Replacements are already ordered (correct value is 250mA as per manual).
![Tweak :-/O](https://www.eevblog.com/forum/Smileys/default/smiliey_cal.gif)
![](https://i.imgur.com/WYLW6Rc.jpg)
Looks of the inside, left back side, mid bottom side, right front side.
![](https://i.imgur.com/jK4mqB6.jpg)
Various switches, this transmitter has a few of them.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
Mains switch, frequency range switch (top side), frequency range switch (bottom side), attenuator switch (coarse) with red resistors, switch internal / external modulation and a switch at the banana socket, disabling the internal capacitor for the 400Hz oscillator when an external capacitor will be used to change the modulation frequency between 200Hz and 4000Hz.
![](https://i.imgur.com/vBITQSh.jpg)
Detailed views of some parts.
Rectifier (not sure, if this is a selenium rectifier), electrolytic capacitor with datecode 4/63, the variable capacitor for tuning the frequency, trimming capacitors to trim the frequency ranges (e.g. after changing the oscillator tube), one of the oscillator tubes, I think this one is for the 400Hz oscillator (unverified)
![](https://i.imgur.com/mM79fhS.jpg)
This is a mod of the rectifier tube. I think, it is related to the notes from above but I haven't checked this yet.
Detailed view of the frequency scale.
![](https://i.imgur.com/CP3vPU9.jpg)
I hope, you've enjoyed this teardown. Please stay tuned for part two: the two transformers.
Thank you for watching.