German radio - schematic symbols

[W1GFH]

Restoring a Grundig 2070 table radio from the 60s. Got hold of the skizmatic and note the odd and inconsistent markings on the cap symbols. Does anyone know what the white and black dots mean? If it's polarity, which is + and which is - ?

[KA1ZGC]

Geez, they even put umlauts on their schematic symbols!

Since the dots are on the same side of the cap and always facing away from ground, their presence would seem to indicate positive polarity (assuming the supply negative is tied to ground).

Beyond that, what their colors might indicate is a mystery. Perhaps composition? Whatever the dot colors indicate, there's only a maximum of four choices (2 dots X 2 states = 4). Think of something about a capacitor that you can use to sort it into four or less categories. Looks like they have some other interesting markings for other properties.

This is one of those projects where engineering meets archaeology. Now you know what it feels like to be Indiana Jones disarming a booby trap based on wall markings written in a language that hasn't been spoken in millenia! 

[k4kyv]

Geez, they even put umlauts on their schematic symbols!

I would say that the side with the umlaut is the "hot" side of the capacitors and the other side ground.  I don't  think 47 and 22 pf caps would have positive and negative polarity.  I don't see how it could make much difference in micas, but with paper capacitors, the ground end is the outside foil and the "hot" end is the inside foil.  If the proper side of the cap is grounded, the outside foil also acts as as shield.

[W7TFO]

On the caps, I'd say it was a shorthand for the voltage rating.  The dot arrangements seem to track where they are located in circuits, voltage-wise. 

A lot like the resistors, with the 'semaphore' legend probably stating the Watt rating.

dg

[k4kyv]

I despise those capacitor and resistor markings that use "color code" but with numerical digits stamped on the case in place of painted bands or dots.  Must be something mandated by ADA to accommodate the color-blind.  Besides being fundamentally a PITA, half the time, enough of the printing has flaked off that you can't make out the numbers.

Another point of contention is when they stamp on a number followed by "M".  I never am sure if it means X a million (megs) or X a thousand (mille).  I have seen it done both ways.  68M - is that 68,000 or 68,000,000?

[W1GFH]

The dot arrangements seem to track where they are located in circuits, voltage-wise. 

Thanks, that sounds right. What a weird system. The 2 section cap symbol is really counter intuitive. I like the US skizmatic scheme better where the lytics are the only caps with polarity, making them easier to spot.

[WU2D]

Joe,

Coincidentally I just submitted a paper called Meissner Regenerated to the AWA Review. I have been redrawing some of the old German schematics over the last few weeks.

Can you guess what this device is?

Mike WU2D

[Ian VK3KRI]

Can you guess what this device is?

Mike WU2D

My initial thought is its some sort of self oscillating amplifier followed by a detector (autodyne?),  however the generator providing B+ makes me wonder a bit.
                                                               

[W1GFH]

Joe,

Coincidentally I just submitted a paper called Meissner Regenerated to the AWA Review. I have been redrawing some of the old German schematics over the last few weeks.

Can you guess what this device is?

Mike WU2D

I see tuned circuits on both input and output...uh, is it a preselector/preamplifier?

[Tom WA3KLR]

Joe,

Your Grundig circuit looks like it could be a switchable in-line VHF r.f. amplifier (on/off); remove plate supply and the input signal is able to bypass the tube stage.? OR reflex converter stage.

[W1GFH]

Joe,

Your Grundig circuit looks like it could be a switchable in-line VHF r.f. amplifier (on/off); remove plate supply and the input signal is able to bypass the tube stage.? OR reflex converter stage.

Yup, a converter, could be that, too. In any case, that skkizmatic's not from my Grundig. It's Mike's Meissner "mystery" circuit for an AWA article.

[WU2D]

This old stuff is fun. Meissner was using a new soft valve technology.

That 1913 patent by Meissner describes a regenerative amplifier which gives improvement over a 1911 Patented circuit by Von Bronk, another Telefunken engineer. It appears to have three modes, as a simple RF amplifer, as a regenerative preselector and finally as an autodyne (direct conversion with full oscillation) for CW reception. The device is the Lieben Valve which was a soft triode Thyratron. This tube with a slightly weaker vacuum was competitive technology to the hard valve Audion. The device uses mercury and glows blue and has (had) a gain of over 30. The patent diagrams do not show the (required!!!) filtering needed when using a DC Dynamo supply in a receiver, nor do they show the rheostats in the cathode. The cathode by the way, is directly heated and is a zig-zag, the grid is perforated disk of aluminum and the plate is a spiral. This device generated 12 Watts in an oscillator in 1913 with 420V on the plate and an AM transmission of over 36 km was accomplished. That weird tube on the bottom is where the mercury lives and you guessed it - it is called the appendix! 

[Opcom]

commas are for decimal points. The Euro folks also like the nanofarad nF..

[Rob K2CU]

European convention uses the multiplier symbol, K, M, tc in place of the decimal. R is used for time 1. ie.

R47 = .47 Ohm
4R7 = 4.7 Ohm
4K7 = 4.7K Ohm
4M7 = 4.7M  Ohm

for caps you have n and p

10n = .01 uF
3n3 = .0033 uF = 3300p
100n = .1 uF
68p = 68 pF

[W1GFH]

uh, is it a preselector/preamplifier?

...a simple RF amplifer, as a regenerative preselector and finally as an autodyne (direct conversion with full oscillation) for CW reception.

I guessed 2 out of 3! What do I win?