5u4 in the RH-84 circuit

[nyazzip]

i know it has been argued about before, but i was wondering if there is a clear "yay" or "nay" school of thought on this? i basically would like to use one because it looks cool and i have a couple. as it stands i think i can stand to lose about 30v anyway so efficiency is not (at least i think so) a huge concern.

[TerrySmith]

So long as you have a 5v 3a heater winding it will work fine!

[nyazzip]

uh yeah i might have a problem there. 3 amps, i just looked it up. zoiks! i do have a 4x el84 chassis that uses a 5u4...but that would be a waste of a transformer. i never dreamed it would be 3 amp draw. BUT, now that i know, is it possible to find suitable filament transformers for this, or should i just forget it?

[Geek]

Directly heated tubes love their filament current

Wait until you play with some big DH transmitter tubes for audio....

The GZ34 rectifier draws under 2A.

Cheers!

[nyazzip]

The GZ34 rectifier draws under 2A.

maybe, but one gz34 will cost as much as a nice filament transformer....the NOS 5u4s are 5$...now i think i know why

...i haven't given up, there are still quite a few hammond organ donors that used 5u4s i think. i just bid on one, 3 bucks. i think i may just win the "worst power-to-weight ratio" contest with this thing....power tranny, 10h choke, overkill OPT, and now a 3 amp filament transformer, all for what, about 1 watt....?

[Geek]

Oh good grief.... the HEADPHONE crowd does that for milliwatts!

5U4's are one of the best sounding of the rects... I'd do it if I were you

Cheers!

[DeathRex]

5R4? The specs are close to a 5U4, 5V 2A, and there's a tater masher version, the WGB. More letters at the end is a good thing.

[EWBrown]

In an RH-84 circuit, the demands on the rectifier tube are relatively modest, so that the relatively inexpensive
Sovtek, J/J or even those "Made in Chian" 5AR4/GZ34s would be good to utilize. Plan "B" would be to use a 5Y3GT,
as it also has a 2A filament, as opposed to the 5U4GB's hungrier 3A requirements.

The flat-top 5R4 "Tater Masher" definitely has its own coolness factor, even if it does "lose" about 30V in the process.

/ed B

[nyazzip]

ah but you see i already have a couple 5u4gbs......
hypothetical question: let us say i did exceed the current rating of a filament winding- would it be instant destruction, or a gradual heating/smoking over the course of minutes or even hours....? i am tempted to try and see what happens; lots of old iron seems conservatively rated/applied. if my pa-774 can run as hot as it does without meltdown, then maybe its worth a shot.
i do have 5y3s and ez81s/6ca4s at my disposal but i was really wanting to light up a big bottle for effect.
maybe check the "prebay" section" soon for some 5u4s.....?

[EWBrown]

You could always go with an 83 (Mercury Vapor Rectifier) , if you like big bright glowy things

[battradio]

This Magnavox came stock with a 5U4GB and 6BQ5's , the Edcor's didn't , I added them in for a customer , when I recapped it .

The 5 watts that a 5U4 draws in power , compared to a 5Y3 or 5AR4 isn't going to mater in the long run , most power transformer are over built that much .

[nyazzip]

ok i think i lined up a filament transformer....will 1,000 amps be ok...?

http://www.ebay.com/itm/KNOPP-TESTING-L ... 35c4e5cd88

[battradio]

Is that on the primary or secondary side

[mesherm]

Take a 6.3 vac tranny and put a paralleled pair of diodes with their cathodes head to foot in each leg of the secondary. That should drop the voltage to 5 volts.

[TerrySmith]

A type 80 rectifier tube will work great, especially if you are going for looks too! They came in the ST and balloon shape.

Also there's the Russian 5U3C that's a really cool looking and rugged tube.