AE EP#22 Electron Tubes Basics & Example Amplifier Project

In this video I quickly cover the electron tubes basics and show a little tube amp project, that uses the 1T4 (DF91). The 1T4 is a low voltage tube that can be operated from 45 (it actually works with 12V too) up to 90 VDC and a heater with only 1,5 V. It is also very cheap and can be as NOS for about 0,5 to 1€.

To make more bang I just put two tubes in parallel. In my configuration the whole set-up makes about 150 mW of sound power.

Find the circuit I followed at: (german)

AE EP#21 Minerva Minola 3 Teardown

This is just a short teardown of the classic austria-made Minerva Minola 3 radio from 1967/8.

Here the promised pics:

Full front view of the Minola 3 in all its glory.


The two Varicaps:
Up: the gear to the varicap on the pcb.
Below: LW and MW system.


External speaker connector on the left, back in the middle the impedance transformer for the speaker and on the right mains transformer with fuse holder.


Front-panel switches and pcb from below.


The main board mounted on the chassis with tubes. The paper in the middle acts as a diffusor for the front panels back-light.


I’ll post an update if I ever get the schematic to fix the Volume pot.
Find out more at:
More about Minerva at:
Nice holidays to you all!

AE EP#20 Industrial Controller Teardown & Homebrew Scope Ideas

Hi, I just started a dream project: Building an oscilloscope from scratch. Originally I wanted to use a russian 13LO37I but it turend out to be too bulky so I went and scored a waaay smaller 3KP1 / DG 7-113 from ebay.
I’ll put up a high res Photo of the tubes weiring system at my website.

One of the first portable TV-sets:

The DG 7-113 / 3KP1’s wiring system:

The russians 13LO37I / 13ЛО4И:

I found the first plans at Jogis Röhrenbude: