This writing is clear and correct.
On December 17, 2016 at 14:58, highfigh said...
I should have written that the voltage from the primary increases in the secondary before it reaches the rectifier.
We know:
-the PT always works with AC and the ratio of secondary to primary winding causes the increased AC voltage at the secondary output (or decreased, since the heaters use AC voltage, too).
-the rectifier and filtering is where AC is changed to DC and the reason I wrote "may be" is because diodes don't drop the voltage much, unless Zener diodes or some other device/network is used to recreate the effect of the original tube(s) in the half or full wave rectifier.
Yeah, but people who don't know that even solid state rectifiers have a forward voltage drop will never understand diodes. It's to their detriment to write "may" have a voltage drop.
-It's not DC until the filtering has been done.
For all of the precision in line voltage that we would like to see, it's not always necessary unless the equipment is built to similar tolerance and is operating at the upper limits of the device specs. If they leave enough headroom, normal fluctuations don't do much damage but the fast spikes can take their toll.
Here's an example of something that shows what would seem to be sloppy design, or maybe it was just accepting the fact that line voltage and manufacturing tolerances weren't very stable at the time- at the upper right corner, the diagram shows "voltages read to ground with electronic voltmeter values shown are + or - 20%".
I'd vote for" accepting the fact(s)."
In my amp of this model, I have read over 530VDC at the plates with a solid state rectifier that is sold as a direct replacement (pretty irresponsible, considering the fact that many people would never think of/bother with re-biasing),
AMEN BROTHER! Solid state drops are less than a volt; that 5U4 I looked up had 50 volts of drop, so replacement with solid state would likely increase the B+ by an unacceptable amount.
but the filter caps are rated for 600WVDC, so they still had some headroom. When I installed a tube rectifier, the voltage at the various test points was almost exactly as shown.
[Link: ampwares.com]Excellent, informative, and accurate. Thanks. You'll never get complaints about the facts from me when you write like this.
