N Cook wrote:
J M Goodey wrote in message
...
The message
from "N Cook" contains these words:
N Cook wrote in message
...
snap almost
Cured the main troubles in valve preamp and amp, suspect EL84 and 2
badly
soldered pcb wire links (lead free solder again, note only 2 or 3
years
olkd) . But there is a low level throbbing rumble noise
obviously associated with the tremolo oscillator on the effects board,
as
it
cycles up and down with varying tremolo pitch and depth.
The owner lives with this but is there a simple cure, assuming its a
grounding/screening/decoupling/smoothing problem.
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.ne
Can anyone say for what mucic reason there is a valve/tube rectifier in
this
amp rather than 1 or 4 silicon diodes ? Loads of op-amps so obviously
not
overall faithfull to 60s technology
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
A valve rectifier will start providing H.T at the same time as the O/P
valves draw current.
If a diode bridge is used the H.T may rise above the working voltage of
the smoothing caps until the O/P valves start to draw current.
--
Jocelyn
Tetigisti acu. (Titus Maccius Plautus 254 - 184BC)
I'd not considered that, but a thermistor plus Si diode/s would avoid that
potential problem. o/p valves for the soft limiting in overdrive but a
thermionic rectifier seems unjustified/unnecessary instead of diodes plus
thermistor.
Maybe it`s the monetary and snob value of having the words vacuum tube
rectifier in the blurb. Some amps have both ss and valve rectification,
switching from one to the other does produce a variation in the sound.
Ron(UK)