The labels are just test measurement labels for selecting matched or quad
pairs out of their valve bins. Email the supplier for correct readings for
your amp as it all depends on the resistance value of the output valves
cathode resistors as to what your actually measuring in relation to the
current through the valve.

If the bias is read from that point you can always see what the value of
cathode resistance are and use ohms law to calculate the anode current from
the reading you get on your multimeter at the test points... EL34's aren't
they usually arround 50mA? Its so long since I've used '34's ;-)

Mike

"Keith G" wrote in message
...
OK, another one for all you who haven't managed to get a box at the opera
tonight:

My recent Chinky EL34 amp acquisition comes with fixed bias and trimpots
and no damn instructions. I don't know - is the *bias* fixed by the valve
type, the circuit (which I suspect it does) or by this figure which all
four valves are (rather conveniently) labelled with:

'1a: 31 mA' and 'S: [nothing]' - (wossat one?)

as per:

http://www.apah69.dsl.pipex.com/keit...pychinky08.jpg

....and any idea what the voltage might be and would it be + or - ???


I'm not yet au fait with the thermionic ping-pong games that actually go
on *inside* valves - only the broadest principles. (The only other amps
I've got that require bias adjustment rather conveniently have the voltage
printed on the chassis!!)

TIA

(out now, back later)