RE: ds821 dx7 servo defect
FWIW (for what it's worth)
If anybody else tries servo tests . be certain the power supply to the servo is constant voltage .
That is: a reading of 70 inch ounces at 4.8 volts means just that .
you start with 4.8 volts and throughout the test, the voltage remains 4.8 volts.
FWIW - you simply can NOT do this with a battery, such as we use for our models .
You need a "constant power supply". That is how the servos are rated and tested.
Here is why: the voltage of a 4.8 battery -freshly charged , is way above 4.8 volts (measure it)
Once a load is induced, -the voltage will drop as load increases .
Depending on the battery used (type size and condition)-this may go to zero.
Here is picture of a device (Whattmeter) being used to measure load and battery changes - Iwas testing batteries in this example.
The applied load (70 ounces in this case) is on a constant radius-such as a string over a 2" diameter pulley.
the distance from pivot to load is constant.
A real problem you can run into is burning up your "test" servo.
Once the servo stalls- internally the heat rise goes nuts - and the only saving possiblity is that the battery has dropped effective voltage and the total current is not enough to instantly fry the servo -in any case,
NEVER hold a servo in a stalled condition - any servo -