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When does a 5V4G/GZ32 have to be replaced?

Hi all, this is my first post here, and I would appreciate some help! :)

I have a custom made pre+amp built on 4 triodes and a 5V4G rectifier. The triodes are relatively easy to keep an eye on (I am measuring the cathode current), but what about the rectifier? How do I test whether it is still in a good shape (preferably, without removing it from the socket)? Would measuring the actual filament voltage (that is directly fed from a secondary winding) tell me whether the tube is still alive?

Thanks!
meisterfloh
hifihvn
943 posts
 
This is part of my concern. When you look at the diagram for the 5V4, the cathode and heater are tied together. That will put the voltage of your filament to from what I learned. Actually, they refer to pin 8 as both the heater, and cathode.

With this in mind, I believe you'll have the high voltage in your filament transformer too, and reason for the risk. I'll post the link below. If it doesn't work, just copy and paste. Might be to small, or something their system doesn't like about some small, and real large links.

I don't now if there are any common rules for the way the tube would act. They seem to lose voltage, and current when they get weaker. Sort of like a tired car battery acts. The lights get dim (low voltage) and it doesn't have the current to spin the starter fast enough. All amp designs would probably act different as the tube rectifier tube weakens. So the B+ high voltage should stay in the range the amp designer wants it to be.

The one tube link is from Jea48's post(Sylvania) , the other is from a RCA manual. You'll see they both agree with the pins being tied together, like I mentioned, that will put the high voltage on the filament supply in any amp they are in, including yours. [http://www.r-type.org/pdfs/5v4g.pdf] [http://www.tubezone.net/pdf/5v4.pdf]
hifihvn
943 posts
 
Meisterfloh, I forgot about this. I don't know of any email notification from them. You can put a link at the top of your search page to click on, and see what changed as far as other people posting on your thread, and any threads you may have posted an answer on.
hifihvn
943 posts
 
Even if it was a 5U4, there will be dangerous voltage everywhere. Maybe read some tube theory books. It's to hard for me to explain. A long time since I learned this. Some are directly heated, others are indirectly heated. The risk is still there with both. 5U4 link. Plus RCA tube manual links that have some theory about tubes. [http://www.tubezone.net/pdf/5u4.pdf] [http://www.tubebooks.org/tubedata/RC20.pdf] [http://www.tubebooks.org/tube_data.htm]
Post removed 
jea48
4,486 posts
 
I do have schematics of my amp. In particular, unlike the Dynaco, in my case 5V4G has its own secondary that is used just for its filament, so there is no high potential there.
06-21-11: Meisterfloh

If you look at the data sheet for the 5V4 you will see pin 8 of the tube is common to one side of the filament and the cathode. Lethal full wave DC voltage from pin 8 on the tube socket to the metal chassis (B-).

Yes you will measure 5 volts AC across #2 & #8 of the tube socket but if the meter probe was to slip and short 8 to chassis (B-) sparks are going to fly big time.....
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