22 Apr
2005
22 Apr
'05
5:25 p.m.
Subject: Re: small valves
From: ard at p850ug1.demon.co.uk (Tony Duell)
Date: Sat, 23 Apr 2005 00:32:48 +0100 (BST)
To: cctalk at classiccmp.org
I have a UK battery/mains radio that uses valves throughout (even the PSU
rectifier) and directly heated valves in the signal stages. The filaments
are in series (carefulyl ordered to get suitable cathode bias voltages),
for a total of 7.5V. The batteries were a 7.5V LT and 90V Ht pair. On
mains, there is a mains transformer, the output of which is full-wave
rectified (EZ40 IIRC). That provides the HT (B+) directly, and the
filament supply (A+?) via dropping resistor.
I have an RCA AM broadcast Battery/mains radio that I still use.
Works well. The multivoltage battery though bad supplied the
authentic looking cover for a box I'd made using uses NiCds
to run a switchmode supply to provide the A,B and C voltages
required. Runs for hours on that too.
Allison
Kb1gmx