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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

Showing 2 responses by meisterfloh

meisterfloh OP
15 posts
 
Hi Guys,

Thanks a lot! Btw, is it possible to receive e-mail notifications when my thread is answered?

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. The reason I was asking was that I had no idea (neither did the guy who had designed and built this outstanding piece of art for me) how exactly a tube rectifier starts to behave when the tube's emission becomes too low. As the 5V4G is only used to get the plate voltages for the triodes, I would expect that when it starts to die those voltages go down, but that's just my guess; besides, the plate voltages are high indeed, and somewhat inconvenient to measure...

I have access to a (friend's) tube tester, I use that when I buy new tubes, but it would be nice if I could check the condition of a working 5V4G once in a while without a tube tester. And measuring the cathode current allows me sometimes to do things without a tube tester: for example, I match the voltage on cathode resistors of 417A-s in order to find matching pairs. Right now I do not have any issue with 5V4G, I am asking to have this information in future when I need it (the rectifier is the only tube in my amp that I do not know how to watch "locally").

Btw, what is the life expectancy of a new 5V4G?

Thanks for your hospitality here at forum.audiogon, and for your worries not to lose a new member! :)
meisterfloh OP
15 posts
 
I guess you guys are right (and I was wrong), the actual potential on the filament is quite high. Of course, it is still not a big deal to measure, but one shall be careful and not get fooled by the 5V specs :)

Anyways, I guess I have no reason to worry as long as everything sounds as perfect as it does, thanks for your answers!
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