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Patrick Turner
 
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Robert Casey wrote:

BoB wrote:

What's the best NOS 5Y3 Rectifier for a 5F1 Tweed Champ?


It shouldn't matter as long as the rectifier tube you have in the amp is
producing full emission. Where it might make a difference of what brand
of tube is used would be in the low level signal processing circuits. And
that is mostly subjective even there.


The 5Y3 was one of the most commonly produced tubes around the world.
There was one in nearly every mantle radio and early radio-gram.
It is an octal based rectifier, and a descendant of the type 80,
which was used in radios from the 1920's.

I'd agree with Robert that as long as the one you plug in works OK, it
shouldn't
make any difference to the sound.
These are really simple tubes, with a directly heated cathode and two anodes
which are the only things within.

But yesterday I had a guy bring his newly bought valve amp kit for a check
over
after he'd assembled most of it.
The supplied Ruby chinese made rectifier was a 5U4, but when we plugged
in and turned on, I got a hum and no HT, and I then found one anode
was bent over against the cathode, which shows you just how shoddy
the quality control must be in china, or in the US where the kit was supplied,

although I suspect the kit was really put together by somebody in asia,
because I've seen the same collection of crummy parts and poor layout before.
I used a GZ32 I had laying around, and all was well, and the amp
sounded fine even though it only made 1 watt from each channel with an SV11.

I have had trouble with other chinese made rectifiers.
I am not saying they are all crap, but I'd more likely trust NOS!
There should be no shortage of 5Y3 around.
Tube rectifiers when operating well within ratings tend to work
for a heck of a long time.

It is possible to use an alternative to the 5Y3.
GZ32 and GZ34 might do OK, although with GZ34, you will get a
slightly higher B+ because the internal diode resistance is lower.
This being the case, it is possible sometimes to add another RC filter section

in the PS, as well as increase the C1 of the CRC filter from say 16 uF to
47 uF, which will also reduce hum on the rails.

In old radios which are not extremely collectable,
I sometimes remove the tube rectifier completely, solder silicon
diodes to the socket, add another C of 47 uF, and another R and change the
usual
low value 16 uF or 8uF to 47 uF or 100 uF, which are smaller than the old
caps, and thus the hum is vanished from the radio.
Unfortunately, most of the hum in old restored AM radios now comes from a
modern source of interference, bloomin switchmode power supplies.
Somehow the radio station you wanna hear is marred by a 100 Hz rasp,
but away from the station, the set is very quiet.

Patrick Turner.