Rectified HT before 5AR4 plates?

[JoeK]

Probably a newb question but: Just looking at a Hotcat power supply and the HT is rectified through N4007s then joined between pins 4 and 6 (anodes) of the 5AR4. The HT across the 4-6 junction is switched on with a 100uf cap for solid state supply or off for tube rectifier supply. Having the rectified DC fed across the 5AR4 seems to be bothering me but I guess it has no ill effect on the tube? All it seems to do is give the sag resistance and some voltage drop I suppose. I was expecting the 5AR4 to be taken out of the circuit all together but it stays in circuit.
Was there a question in there? Are there any issues with rectified HT across the 5AR4 parallel plates?

[Chuck H]

Considering it I can't think of a problem. It actually equalizes the voltage end to end. With no difference potential, what can happen? Seems fine to me.

[Enzo]

The 5AR4 is a rectifier, think of it as another diode. It conducts one way and not the other. It really has no idea if you are feeding DC through it or AC. It allows things to pass in the right direction and blocks anything wanting to go the wrong way. The tube doesn't care.

A schematic link would be great for discusion.



I found a Hot Cat 30 at Schematic Heaven, is this your amp?
http://www.webphix.com/schematic%20h..._hotcat_30.pdf

If so, when I read your description I see something different than this circuit.

For example, the AC is not rectified then sent to the tube. The AC goes to the tube and the diodes. If the switch is off for tube operation, those diodes disappear - they don;t go anywhere. Normal tube rectification. Turn the switch on, and the diodes shunt right across the tube - the tube disappears. The tube is still thyere with voltage on it, but no current flows through it. It has diodes across it now. All the current takes that leisurely 1 volt drop instead of pushing through the tube and losing tens of volts to it.

If you wire across something, it pretty much removes it from a circuit. No curent will flow through a thing with a bypass. No harm, no sag, no nothing.

[Chuck H]

If you wire across something, it pretty much removes it from a circuit. No curent will flow through a thing with a bypass. No harm, no sag, no nothing.

As in, no voltage difference.

[JoeK]

Yes that schematic seems to be the only one available on the web and I've looked at it a few times but I'm looking at two early-ish hotcat 30 amps and they are wired up with diodes first the 5ar4 unless I'm mistaken. I'll try to load a couple of pics.

[JoeK]

One of the amp

[Enzo]

Well, either way, shorting across the rectifier tube takes it out of the equation. And won;t hurt it.