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diodes across the rectifier socket
Posted: Mon Oct 14, 2013 6:36 am
by Elad E
I've been trying to no avail to find an explanation or photo which shows how to wire diodes across the rectifier tube socket to save the PT in case the rectifier tube shorts.
anyone did it?
is there any downside to doing it?
Re: diodes across the rectifier socket
Posted: Mon Oct 14, 2013 8:41 am
by neikeel
There is one here:
http://www.ceriatone.com/images/layoutP ... iatone.jpg
Personally I do not as I think that if you have diodes then you lose the effect of the rectifier sagging under load (although someone may be able to disabuse me of this opinion with adequate explanation!
Ah I 've look closer they go to unused pins on the socket and have the cap between the outputs, so not actually in parallel with the tube
Re: diodes across the rectifier socket
Posted: Mon Oct 14, 2013 10:27 am
by VelvetGeorge
I've never seen a rectifier tube fail and take out the PT in an amp that had the right fuse value installed. Most commonly, a screen shorts in an output tube which can also take out the screen grid resistor, a power supply diode and, in the case of the fuse not protecting it, a PT.
george
Re: diodes across the rectifier socket
Posted: Mon Oct 14, 2013 11:48 pm
by VelvetGeorge
I was thinking about this. Diodes in series with the plates (pins 4 and 6) could work as a fail safe. If the rectifier shorted would still be providing rectified DC voltage.
You could use the open pins on the rectifier tube socket to mount the diodes. just be sure to move the HT wires from the PT to the diode anode. On pins 3 and 5, for example.
george
Re: diodes across the rectifier socket
Posted: Mon Oct 28, 2013 11:07 pm
by ivan H
Hi, I know this answer is a bit late, but here goes.
I asked about this a while back on another forum & was answered by Kevin O'connor, (author of "The Ultimate Tone" series of books), saying that the unused pins on the rectifier socket were for voltage isolation purposes & that it wasn't really a good idea to be using them. He also said that putting the cap across the diodes should be avoided. He advised using a single diode in the B+ line (straight off pin
to protect against AC on the output tube plates should the GZ34 ever fail. I did post about some time back, in the "beginner's questions" sectlaion I think. Hope this helps. Cheers
Re: diodes across the rectifier socket
Posted: Tue Oct 29, 2013 6:27 am
by neikeel
ivan H wrote:Hi, I know this answer is a bit late, but here goes.
I asked about this a while back on another forum & was answered by Kevin O'connor, (author of "The Ultimate Tone" series of books), saying that the unused pins on the rectifier socket were for voltage isolation purposes & that it wasn't really a good idea to be using them. He also said that putting the cap across the diodes should be avoided. He advised using a single diode in the B+ line (straight off pin 8 to protect against AC on the output tube plates should the GZ34 ever fail. I did post about some time back, in the "beginner's questions" sectlaion I think. Hope this helps. Cheers
Thanks for posting - I'l store that one away (Mr O'Connor seems to be a reliable source!)
Re: diodes across the rectifier socket
Posted: Tue Jun 24, 2014 4:57 pm
by mercimek
@Elad E: Hi, you can use the diodes to protect the rectifier tube from the surge current and for this purpose the anode of the diode should be connected to AC side of socket and the cathode of the diode should go to the DC side of socket.
