Siemens Echo Encephalograph Teardown
In early 2012, I bought a very peculiar machine from a friend, who bought it from the junkyard. After looking inside, there were some seriously damaged circuits, so I thought it was not worth restoring it. The best decision was to tear the machine down to reuse the – extreme good quality – parts. I took several photos of the process, but I will only publish the best ones.
Full of dust and dirt.
The leather handle is not in very good conditions.
Things I found lying inside: a broken tube, a 6AQ5 tube (not related to the machine), a battery, a screw, a washer and a pin.
Here you can see a huge crack on the PCB.
It was very late, so I left everything for the next day.
After serious cleaning, it looks like new, and the text is readable.
- Netz: Power (on);
- Schärfe: sharpness (focus);
- Nullpunkt: Null point (center);
- Masstab: Scale;
- Prüfbereich: Test area;
- Impulsstärke: Pulse strength;
- Tiefenausgleich: Deep balancing;
- Verstärkung: Amplification;
- Skalenbeleuchtung: Scale lighting (a rheostat to adjust the brightness of lamps that light the scale);
Close-up of the stylized text and input connector.
Main board, right section. The black box with the tube is a high voltage generator for the CRT, and the only part that was completely intact and I managed to make it work (the CRT is intact also, but I never was able to test it).
An interesting feature is that the two main boards have hinges. All the tubes on these boards have an aluminium shielding, to avoid high frequencies from one tube interfering on the functions of another, and vice-versa.
Left to right: E 130L (power beam tube), AG5121 (gas filled thyraton, works like a SCR), E80CF (triode-pentode), E83F (pentode), E188CC (double triode).
Close-up of the high voltage generator. It’s a common Hartley oscillator setup.
Another close-up of the right board.
“Calibration in cm”.
Main board, left side section. The upper board is (probably) the power supply, as it has a solid-state bridge rectifier (hybrid technology!), a 150B2 voltage regulator tube, and some filtering capacitors.
This board (probably) houses four HF oscillators, judging by the presence of adjustable coils and the low value, silver mica, capacitors on the other side.
Shielding removed. Left to right: E188CC (double triode), 5*E83F (pentode).
The said filtering capacitors, and a board covered in some kind of wax, to avoid arcing.
Close-up of the solid-state rectifier, and the CRT shielding.
Upper side: Two EL34′s at the power supply board.
Front cover removed, showing the scale and it’s lighting system.
One of the boards after being removed. Here you can see that the crack goes through the whole board, one side to another.
Power supply board. Left to right: 2*EL34 (pentode), E80F (pentode), 150B2 (voltage regulator).
Oscillator board. The missing tube is probably the broken one.
Tiny board full of resistors, and two capacitors.
The power supply transformer, weighing about 4kg(!). The metal box houses a filter, to avoid interference from and to the mains grid.
Transformer wiring detail.
I was not going to add this pic, because the focus is terrible here, but reading “Made in W. Germany” is somewhat funny nowadays.
Then it gets pretty boring: I removed the tubes from their sockets, desoldered everything else and stored the parts for later usage.
After searching the web for information about this equipment, I could only find these: