Uncle Peter wrote:
"Antonio Vernucci" wrote in message
t...
Measure the supply voltages and compare with the schematic. If they
are all too high, add in a dropping resistor.

Putting a series resistor would degrade the power supply regulation
performance. This may or may not be important, depending on application.

Yes, but it will degrade it to the same level which using the original
rectifier tube would.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Putting a series resistor would degrade the power supply regulation
performance. This may or may not be important, depending on application.

Yes, but it will degrade it to the same level which using the original
rectifier tube would.
--scott

A vacuum rectifier shows a non linear behaviour, whereby the voltage drop vs. current tends to saturate (until one exceeds the rectifier rating). So, using a resistor to simulate the vacuum rectifier voltage drop, would cause a worse regulation around the rectifier operating point.

But even disregarding the above consideration, putting a resistor instead of a zener diode would mean losing a chance to improve things.

73

Tony I0JX

Bob,
Yes.
I happen to be restoring an HX-50 at this time. I believe the rectifier
tube is a 5R4GYB. The specs can be found on an application at:
http://tdsl.duncanamps.com/ (I use it a lot); There is it specifies a
voltage drop of 63v at 250ma DC. Also PIV=3100; I Cathode is 715ma max;
IRect is 250ma; RMS input is 900-0-900v. Also see ratings chart at:
http://tdsl.duncanamps.com/pdf/5r4.pdf . The final setting of the resistor
will ultimately be determined by obtaining the proper B+.

Some one did the same thing to the unit I am restoring. So I will be doing
the above exercise too.

Were did you get the 500 volt electrolytic?

I hope this helps.

Paul P.

PS - I'd like to hear about your experiences. I am trying to get a clean
schematic. BAMA is missing significant parts of the schematic art work
around the Power supply 5R4.


wrote in message
ups.com...
Is the voltage drop across a vacume tube rectifier significantly higher
than a solid state plug in replacement? Previous owner of my HX-50
changed over to SS. I am changing out capacitors and just curious.

73
Bob
N9NEO