Try getting some dielectric lubricant into the top cap. I've had no issues with the Chinese adapters so far.

Just get a 5Y3G and be happy. There is a nice Silvertone 5y3G on the auction site for $22.95, $7 shipping.

Those Ferranti’s are a steal! Sound great. I think I have bought my last 807s, at least for a while lol. I now have the Ferranti, Cossor, Mullard, and just today I got in some Fivre and Mazda as well. Also have some funky loctal 807 from STC that needs an adapter. I will definitely get some more 6bg6ga tubes in the future though. They are related to 807.

Well....
 

First off a disclaimer.

Tube amps that are powered up contain LETHAL voltages. One must always be very careful when sticking your hands or tools attached to your hands inside one, even one that has been powered down. The big power supply capacitors can maintain lethal charge for quite some time, especially if the power supply has no bleeder resistor to drain off the accumulated charge. Always better to stick one hand in your pocket when working on one, and to wear shoes with rubber soles, even flip-flops. Bare feet on a concrete floor like my workshop is asking for it. I would also wrap any needle tipped probes with some shrink tube so that only the most distal tip of the probe is uncovered. Shorting out components under full operating voltage may very well let out the magic smoke.

Can you read a schematic? Solid State schematics differ somewhat from toob schematics due to different types of components used. Anyway, to measure the power transformer output, you measure the high voltage output leads as they connect to the rectifier socket. This will be ACV.

Then you measure the output voltage, either at the socket or the + terminal of the first capacitor after the rectifier. This is DCV, and measured w.r.t ground, i.e., measure with the red meter lead on the positive terminal and the black lead on the negative . That will give you the voltage drop of the rectifier. Simple, no?

Is it ok to use a 5Y3GT rectifier with 6V6GTs?

Instead of taking the bottom of the amp off and poking around a live amp, could I use something like this?

https://www.amazon.com/Nobsound-Vacu...ps%2C77&sr=8-4

If that gives me the bias current couldn't I use that number to figure out the voltage somehow? Isn't this built into the current Firebottle amps now?

3 for 3 now. I just bought it even though I was contemplating other more expensive alternatives. Brent Jesse was very high on Bendix, Mazda, and Brimar all at $99 each.

Messaged Dennis as well. He said, while the Bendix would work, he isn’t a fan. So there’s that. He had suggested a coke bottle shaped RCA of GE 5Y3G and the Silvertone (is that a manufacture or relabel) fits that criteria and seemed in line with the price I paid for the Fivres.

Oh this just occurred to me, which rectifier for the 807’s (still finalizing the adapter)—the 5U4G or the just bought 5Y3G?

You can use either. The 807 can handle more voltage. Giving it less with the 5y3 is bound to change the sound but it won't harm anything.

I use an RCA 5y3 and 5u4gt. Also have a Japanese 5ar4 and a Russian one along with the one that came with the amp. I don't use the 5ar4 though.

Yes, you can use a 5U4G or 5Y3GT. Let your ears decide.

That's why I'm asking. 5U4G sounds great...5Y3GT sounds sublime!