Tube Rectifier and diodes

[mesherm]

I am converting one of my previously built ST70s from UF4007 rectification to the original 5AR4/GZ34. What would happen if I left the diodes in the circuit between the HV and the tube plates?

[Shannon Parks]

I am converting one of my previously built ST70s from UF4007 rectification to the original 5AR4/GZ34. What would happen if I left the diodes in the circuit between the HV and the tube plates?

Don't do it. Yellow_Light_Colorz_PDT_18

You figure it would end up kind of looking like diodes in series. Assuming you hooked the halves up right.

I better drink more coffee.

Shannon

[Ty_Bower]

Shannon,

Did you ever get your coffee? I just ran across this same question recently on the diyAudio forums.
http://www.diyaudio.com/forums/showthre ... did=121057

Kevin's comment in post #13:

I have been using UF4007 in this same topology for over 10yrs and it is very effective at preventing arc-over in the 5AR4 and other rectifiers with close cathode to plate spacing. I have not had a single rectifier tube failure due to arc over since I started doing this.

Sounds like an attractive option to me. After all, who wants 5AR4 arc over? What's the disadvantage? Why shouldn't we do it?

[Slartibartfast]

I am converting one of my previously built ST70s from UF4007 rectification to the original 5AR4/GZ34. What would happen if I left the diodes in the circuit between the HV and the tube plates?

Don't do it. Yellow_Light_Colorz_PDT_18

You figure it would end up kind of looking like diodes in series. Assuming you hooked the halves up right.

I better drink more coffee.

Shannon

Would that not be parallel?

[mesherm]

I don't even remember what amp I was originally referring to...
Yellow_Light_Colorz_PDT_04

I have used two UF4007 diodes in series without problems though so I don't see why having UF4007s in series with a tube rectifier would hurt anything. I'm sure the UF4007 is more effective at reverse voltage blocking and thus spares the 5AR4 from undo wear and tear. Those of you who have had flashover problems with 5AR4s might try it.

[TerrySmith]

I have thought of kinda the same thing: use two UF4007 diodes for rectification, a large damper tube in series between the diodes and first cap for a slow turn on.

Damper tubes such as a 6DW4B, 6DN3, etc.

[sorenj07]

Or you could, I think, put a damper between the HV centertap and ground. I have a couple 6AY3's kicking around.

Quick slightly different question about diodes. If the cathode is completely electrically isolated from the heater, is it OK for a rectifier to share the heater line with signal tubes?

[jeffdavison]

Could try a Hybrid Graetz Bridge....

scroll to the middle of the page and see how it's done with a GZ34/5AR4

http://www.audiodesignguide.com/my/se.html

JD

[Quad]

This might be of interest -

http://www.kitparts.com/51J-Collins/

Schematic here -

http://www.kitparts.com/51J-Collins/A%2 ... eivers.pdf

[Quad]

I found a nice looking schematic using a Si full wave rectifier followed
by a single 6D22S damper tube for slow start.
I guess one could use other dampers like 6CJ3 too.

http://www.vanegmond.net/Audio/preamp.html

[kheper]

Below is a hybrid, full-wave <b>bridge</b> rectifier: 2 diodes and 2 half-wave rectifier tubes.

Advantages for a hybrid: slower turn on. better reverse voltage blocking.

I have never seen a hybrid, full-wave rectifier in operation.

http://homepages.ihug.co.nz/~rwillis/al ... bridge.jpg

[Gingertube]

I had a 5R4 "potato masher" rectifier start to arc on power on every now and again (It did'nt do it all the time just when it seemed to feel like it).

I had seen the idea of adding SS diodes in series with each plate of the tube rectifier suggested before so I tried it. Maybe that rectifier had already suffered some degredation and was now prone to flash overs at switch on but I found it did'nt make a rodents hind quarters difference to the flash over problem BUT for some reason (????) I seemed to get about another 10V from my +340V supply - go figure.

I eventually chucked the 5R4 and subbed a CV717 leaving the SS diodes in place. No problems anymore so I stopped investigating.

So my experience suggests that the SS diodes did'nt do anything much.

Cheers,
Ian

[chrish]

Funny you should mention that Ginger. The guy I get some valve gear from in Singapore sells Sun Audio kits and amps. He puts the built amps together himself. When I stop in he is often wiring one up. I noticed one day that he was soldering diodes to the socket pins of the rectifier. When asked what it was about, he stated that it gives a little more on the B+

Maybe this might an additional way to fine tune your B+ that some might find useful.

BTW, loving the Baby Huey!

Cheers,

Chris