01-11-2018, 07:56 AM
(31-10-2018, 08:27 PM)Ed_Dinning Wrote: Hi Gents, in most instance's a valve type with differing prefix letter will always use the same heater power (V*A), so it is quite easy to make a small auto transformer to act as a "voltage shifter".
As the power is low quite small transformers can be fitted under the chassis. They would also have a low turns count as the voltage is low.
Ed
Fixed valve heater power is one way I was going to try and ID unmarked valves, since you know that anything in a B9G socket will likely not be much more than 6W you could simply apply a fixed power for a given envelope height (PCC83 @ ~2W, PCL86 @ ~4W, PL84 @ ~4.5W, PL81 @ 6.3W for P-series examples) and see what voltage pops up on the pins, fixed power would come from a clever SMPSU with primary side power regulation.
Ed, your Auto-transformer idea is very good, I was thinking about making a valve base 'interceptor' plug and socket, breaking out the heater connections and running them to an AutoTX somewhere else, under the chassis or at the side of the set etc. What would be the cost for such a transformer? I guess only a few types would be needed to convert for common types (E-->PCL8x, E-->PCC8x, E-->PL84).
Dave.
