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
22 Apr
22 Apr
5:49 p.m.
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.
I'm suprised it needs a separate C supply. UK sets all used self-bias by
this time, I think. C (grid bias) batteries were not used for radios much
after the 1930 in the UK.
I have a working Vidor AM/FM valve portable (!). OK, it cheats in that it
uses a few germanium diodes in the detector stage, but there are no
transistors. It's battery-only (officially), 1.5V LT, 90V HT. It's not
much larger than many of the transistorised AM/FM portables that came out
a few years later either.
The batteriers are long-since unobtainable (at least not easily). I run it
from the mains. The LT is triival to get from my bench
aupply. For HT,
I've made a little PSU from common components that gives about
85V (high
enough for the set to work well). It's just a 30V transformer feeding a
voltage doubler circuit. Much easier to get a 30V transformer than
something of a higher voltage now.
I must try the circuit that was in Elektor a couple of months back to get
90V from low-voltage batteries.
-tony
9:09 p.m.
Tony Duell wrote:
The batteriers are long-since unobtainable (at least
not easily). I run it
from the mains. The LT is triival to get from my bench aupply. For HT,
I've made a little PSU from common components that gives about 85V (high
enough for the set to work well). It's just a 30V transformer feeding a
voltage doubler circuit. Much easier to get a 30V transformer than
something of a higher voltage now.
I must try the circuit that was in Elektor a couple of months back to get
90V from low-voltage batteries.
Also with the low cost of power fets a simple zener diode voltage
regulator is peanuts in cost to
do. The only catch is the case is HT in. With a simple one or two tube
set some 5 watt zener diodes
might work better.
-tony
23 Apr
23 Apr
1:18 a.m.
Hi,
Tony Duell said:
I must try the circuit that was in Elektor a couple of months back to get
90V from low-voltage batteries.
See http://hometown.aol.co.uk/kitradioco/uk.htm for a commercial one,
it even looks like a battery. But IIRC you're like me - you don't like
_buying_ things you can make!
--
Cheers,
Stan Barr stanb at dial.pipex.com
The future was never like this!
3:49 p.m.
Hi,
Tony Duell said:
IIRC they're based in Westerham (Kent, but very close to London). It's a
pity they're mail-order only (I don't trust the postal 'service' round
here...), as I could collect from them very easily, and I'd probably have
bought some stuff from them if I didn't have to worry about the post...
I must try the circuit that was in Elektor a couple of months back to get
90V from low-voltage batteries.
See http://hometown.aol.co.uk/kitradioco/uk.htm for a commercial one, it even looks like a battery. But IIRC you're
like me - you don't like
_buying_ things you can make!
Of course not. Making things myself seems to be the only way to get them
even moderately well designed now.
-tony
7183
days inactive
7183
days old
4 comments
4 participants
participants (4)
-
ajp166＠bellatlantic.net -
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
stanb＠dial.pipex.com