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Re: Rectifier Flashing....

66.214.164.44

Posted by steven oda on September 7, 2002 at 11:18:36

In Reply to: Rectifier Flashing.... posted by Derick on September 6, 2002 at 23:29:59:

Derick,

I a bit confused here... as you can tell. When you said that the 5V4 rectifier "flashed" once---but, never again, you meant that the 5V4 is still working, right? Or did it flash and die?

The 5V4 and the 5U4 have pretty close to the same PIV = 1500 volts. The big difference is the MAX current output per plate 275mA DC for the 5U4 and 175mA DC for the 5V4. Peak current per plate = 525 mA (5V4-GA) and 1000mA (5U4-GB).

Now, I know this sounds silly, but I've seen 5Y3GT in 5AR4 OEM circuits. And the amp sometimes runs into problems when it is really pushed and the power tubes demand so much current, that the current draw actually arc-welds the 5Y3GT. The power tranformers on these amps are usually the big over-engineered type.

But, I've yet to see a 5Y3GT (400 mA max peak per plate) fail, when it is replaced into a 5AR4 socket (750 mA) and the amp is simply turned on, under no load.

I use 5Y3GT in most 5AR4/GZ34 amps which I rebuild, to "form" new capacitors. This is because the 5Y3GT is directly heated and therefore the tubes "see" voltage from the first application of AC voltage from the Variac.

I don't keep the 5Y3GT in these amps, but I've yet to have an arcing problem, using them to form new caps, up to max 120 volts AC---where there is no input (volume at zero), speaker attached, power tubes at idle.

I know a lot of folk wince, but some guitarists will put the 5Y3GT into an amp which normally takes a 5AR4/GZ34 recitifer, to give the amp more "sag." Especially, those amps with undersized power transformers. DEFINITELY, not recommended. But, these amps actually work at volume.

Now, since you said that the Mullard 6X4 "flashes" all the time---I have a feeling you are talking about the initial glowing of the heater filament. Since the 5U4-GB has no separate heater filament, you see no flash. But, when you replaced it with that 5V4-G, you noticed the heater filament initial glow.

Does this sound close? Anyhoo... for peace of mind & to keep the rest of the amp happy, use the recommended rectifier in all of your units.

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