"Winston" wrote in message
...
William Sommerwerck wrote:

I'm guessing that the 7.5V specs are for the lowest voltage
the designers felt gave acceptable performance.

I feel that Grundig assumed the service person would connect
their bench supply between rail ground and "battery +",
not between "battery -" and "battery +".

Unfortunately, they call "power rail voltage" and "battery voltage"
aren't the same thing. They are different by 2V in the MW model.

While we're at it... It's perfectly normal for amplifier stages -- tube or
transistor, in any kind of device -- to be fed through a small resistor,
with a largish capacitor to ground. This "decouples" the stage from the
power supply, to prevent feedback. The resistor /is not/ present to reduce
the power-supply voltage.