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

I would not check the voltage on the rectifier tube filament, if that is what your speaking of. The voltage there is several hundred volts, and *deadly*. Even if you could measure it, it wouldn't tell you the condition of the rectifier. The high voltage will be on all the pins. That tube changes the high voltage AC, to high voltage DC. Way to risky unless you no what your doing, and have a good high quality meter capable of handling the high voltage there. Plus you would need a schematic for, and understand it.

Pardon the grammar, I just got worried about losing a new member.

I'll to try to give you a little idea, why you wouldn't measure the 5 volts on the filament. There would be the full B+ plus high voltage on it *also*. That is why it is dangerous. Pin 8(rectifier tube) on this Dynaco amp (link below), has the output from pin 8 (high voltage DC ) coming out of it (rectifier tube) to feed the filter caps, and choke for the B+ high voltage. I don't know your amp, but on this one, that it basically where the high voltage for the B+ originates. With the schematic, it would tell the proper voltage that should be there. This amp shows 480 volts after the choke. Risky high voltage. That's why you need to know what is happening, and I don't recommend trying to measure it. Dynaco Mk3 link [http://www.triodeel.com/dynamk3.gif]

Retry Dynaco link above[http://www.triodeel.com/dynamk3.gif]

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]

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.

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]

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.....

Jea48 (Threads | Answers | This Thread)

That's what I was missing. When I type, I loose my train of thought. And I'm lousy at typing.