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DM70 TELEFUNKEN TUNING INDICATOR, 1960's
Telefunken DM70 Tuning indicator for Battery sets. Used to display the optimum signal tuning point of a tuner/receiver, or the peak signal level of a pre-amplifier or tape recorder. The main benefit in tuning reception was for FM tuners where the exact tuning point was harder to determine than for AM.
The front of the tube has a black area with an exclamation mark cut into it, the dot is illuminated green with a small portion of the top of the mark also green (when no signal is present) as the signal is increased the area at the top of the mark moves towards the dot until it touches at full strength.
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- I have an early 1960's "Mechanism Ltd." Ref: 6C/2366 Precision Aneroid Barometer very much like the Model M1991, but with a wider range of 800-1050 mB. This uses two mercury 28V batteries that are impossible to get now, so I have fitted 5 x 12V camera batteries GP Alkaline type 23AE. As you decrease the value of the mechanical vernier, this breaks a switch that causes the magic eye to suddenly open. The reading on the vernier is then the atmospheric pressure to an accuracy better than 0.1 mB. I bought this device from Ebay in 2004 for £112 as it works perfectly and comes in a very nice case.
.......... Anthony Williams, St Albans, England, 5th of June 2015
- Stereo Corporation of America 9190 receiver
.......... Paul Silberberg, Matawan NJ Usa , 11th of February 2014
- This indicator was used on the Grundig TK1 battery tape recorder as a recording level indicator.
.......... Dennis Cowdery MIET, Reading, Berkshire, 27th of August 2013
- I first came across this useful device in a battery receiver manufactured by Wells-Gardner in South Africa, Later I constructed a portable stereo cassette recorder and used two DM70s as level indicators. The pair gave me a long life and eventually they were used on a transistorised version of the recorder with a small inverter running at 30KHz to deliver 45 volts for the anode.
.......... Graeme.M.Young, Ravenshead, Nottingham NG15 9EZ, 16th of August 2011