Hello All
I know how to measure bias voltages in my Dynaco st-70's and Mark!!'s
from the pre-amp out puts.
How do I do it at the tube, in milli-amps?.
Thanks in Advance
Mike M

in article t, Mike Mueller
at wrote on 3/28/05 8:22 PM:

Hello All
I know how to measure bias voltages in my Dynaco st-70's and Mark!!'s
from the pre-amp out puts.
How do I do it at the tube, in milli-amps?.
Thanks in Advance
Mike M


There is a 15 ohm (approx) resistor installed between the cathode of each
output tube and ground. Measure across each cathode resistor.

Jon

On Tue, 29 Mar 2005 01:22:29 GMT, Mike Mueller
wrote:

Hello All
I know how to measure bias voltages in my Dynaco st-70's and Mark!!'s
from the pre-amp out puts.
How do I do it at the tube, in milli-amps?.

The common cathode resistor in Stereo 70's is 15.6 ohms, so
the 1.56 volts specified is 100mA.

In Mark II's and Mark III's it's 11.2 ohms, so the specified
1.56 volts is 140mA.

They picked 1.56 volts so folks could check their meters
with a fresh zinc battery. Cool, huh?

Good fortune,

Chris Hornbeck
6x9=42