Kipp: Mercury Super Ten (Super 10)

In the very early days of Radio, Superheterodynes were built quite different from their successors 10 or 20 years later.

They had to apply relatively weak battery triodes throughout, even for the output.
Sensitivity was aimed for, to permit use of frame aerials, thus avoiding wire antennas, e.g. in a city, and benefit from directivity and suppression of electric noise from the environment.
Selectivity was not yet achieved by IF band filters. Either transformers (air or even iron core of thin wires) or some times a single tuned circuit did the job.
Contemporary triodes had some problems at higher frequencies. Hence the IF was chosen between 40 to 100 kc. Consequently image reception was unavoidable.

Here is one of these multi tube monsters (they are my favorites...) : the Kipp Mercury Standard also called the Mercury Super Ten.

Circuitry analysis, as from the schematic :

Starting at top left, the Antenna input transformer hat the secondary tuned.
Below the oscillator (tube #1) has the Grid circuit tuned. The grid coil is tapped to feed the input circuit in series. Both signals, input and oscillator, are added and fed to the second tube, the 1st Detector or Mixer stage.

The next four IF stages (tubes #3 to #6) are transformer-coupled, followed by the 2nd Detector, an Audion demodulator (tube #7)

Consequently the IF does not contribute to selectivity, but to sensitivity. Tuning is provided by the input circuit, while the oscillator may be set to a frequency which falls in the passband range of the IF transformers, and whereno other station might disturb (image frequency, 2nd harmonic products etc.).
Gain control is achieved by variable grid bias(400 ohms pot.) and filament control (15 ohms variable). It acts at IF and partly 2nd Det.
Osc., 1st Det., and Audio tubes are at full A supply (via 5 ohms in series)

A transformer coupled 1st AF stage (tube #8) is driving the transformer coupled 2nd Audio (tube #9 and #10 in push-pull). 
A  Loud & Soft switch allows to shunt the secondary of the 1st AF transformer with a 50 kOhm resistor.

The A supply employs two series filament arrangements. That permits use of a standard 6 volt storage battery. The current drawn is ca. 0.5 amps max.

B supply is +67.5 and +135 volts. The latter is the maximum value. It can be less, as sufficient for the desired output.

-C bias has to be set to optimise the currrent drawn from the B battery vs. tone distortion. A tapped C battery of 9 volts will do.
The -C battery might not be required if the output stage works on low voltage.

Antenna reradiation is certainly a problem. The oscillator frequency is going through the input secondary coil to the mixer grid (which certainly draws grid current), plus capacitive coupling to the primary, thus coupling to the aerial. There is no RF stage to decouple. I wonder how that problem was managed those days...

 

 

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I don't know if this is a kit or factory made. The doubt if factory made comes only be the engraved numbers in the wooden parts inside - but the cabinet shows factory made ... Maybe Kipp did this numbering to all early models - maybe for a single process and for assembling instructions.

the metallised and glass sealed shunt (in red) for the secondary of the 1st AF transformer reads 40 kOhm, not 50 kOhm but this is in a normal variation. It has been made by De Jur New York as also the 2 MegOhm (in blue). There is also a spare 2 Meg with it's holder loose in the radio of "De Jur".

The two high volt (200 DC, 300 AC) filter condensers are from Polynet Mfg. Corp, New York. At the oscillator side unfortunately there is a (later) mica condenser of .001 MFD (1 nF). This tube socket was probably renewed and also the first on the other end.

On the front there are a wire rheostat for "Current" and a wire potentiometer for "Volume", both on ceramic.

There is a socket for a connector with five plus two rather long wires. The two are not bound together and do not bear any information. Manually one can see 90V+, 45V+, neg., 6V+ and 6V- for the five wires. I believe the "A" supply (heater voltage) was fed by a led accumulator of 6.3 volts.

Since the variable condensers are round this must have been a rather early set. Some tubes were replaced by U.S.N. CW-38015 tubes (US  Navy).

I wonder when we will see photos and information about an other set here and hopefully also of the later sets (and earlier ones) made by H.M. Kipp Company Ltd, Toronto, Canada.

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