The 555 power supply uses that big heavy saturable reactor to
regulate the heater voltages. It relies on a little tube that varies
its conductivity according to the temperature of its filament and
varies the control current in the reactor, which in turn regulates
the heater supply transformers primary voltage.
And you are correct, the 551 did not have this arrangement.
Bonne Noel.
Larry Christopher
--- In TekScopes@..., "coresta" <coresta@...> wrote:
Hi Stan,
As i see this new thread, i always asked myself about the use of
Kalotron in
the PSU of the 555 ? What's the big iron potted case too ?
I broke a pair of those PSUs many years ago and those are somewhere
in the
basement . I never saw the schematic .
I have a 551 working that doesnt contain these parts .
Ah, happy new year to all of you !
And long life to our old old tubed scopes ;-)
Pierre
