Using a 6AX5 instead of 5Y3

[cannikin]

Been searching the net and have some thoughts but I wanted to post here to see what people have to say about it. Basically,I have some Power Xfmrs without a 5V tap and curious about using a 6AX5 (6.3V) rectifier instead of 5Y3. So far my understanding is that its fine as long as you have enough juice in the 6.3V winding to accommodate the 6AX5.

For example: could I use a 6AX5 to replace the 5Y3 in something such as the Federal Limiter circuit?

Subjective question: Will a unit with a 6AX5 have sonic differences compared to one with a 5Y3? how?

Last Question: what is the deal with Parallel rectifiers 5Y3 etc? what applications would call for parallel rectifiers? do they give better rectification or something?

curious thanks

 

[cannikin]

The 5Y3 has higher Ratings but when your dealing with Circuits that require 200Vdc to 300Vdc -- it really shouldn't matter - right?

 

[bigugly]

5Y3 data: http://www.nj7p.org/Tube4.php?tube=5Y3GT

6AX5 data: http://www.nj7p.org/Tube4.php?tube=6AX5GT

It looks to me like the main differences, besides heater voltages, is the 5Y3 has a higher PIV and more voltage drop than the 6AX5.

I'm not familiar with the Federal circuit but the two tubes seem similar enough to me to be interchangeable in lower voltage situations. ie. less then 350v.

 

[bcarso]

That's a hella heater-cathode voltage rating on the AX5!

One caveat: make sure the 6.3V is referenced to ground. Despite the high heater-cathode rating, there may still be significant leakage, including the thermionic emission of the heater, and without a place for the current to go it will end up biasing the 6.3V in some poorly-determined fashion.

 

[CJ]

Put a frikin resistor in series and quit wastin time.

 

[cannikin]

[quote author="CJ"]Put a frikin resistor in series and quit wastin time.[/quote]

exactly --

Two 100 Ohm resistors to ground/CT -- right?

Ignore the rest of the circuit -- I'm just looking at the Power supply/filter/choke Area

 

[CJ]

2 amps of current for the 5y3 (whew!)
we need to kill 6.2 - 5 = 1.2 /2 = 0.6 ohms.
2 times 2 is 4, right? 4 times 0.6 is 2.4 watts.

Get a 1/2 ohm resistor at 5 or ten watts at Radio Smack.
They should have them as emmiter stabilzation resistors.
Resistor gets placed in series with 5y3 heater only.
were done.
next problem please.

 

[bcarso]

That's fine if the 6.3V winding is not the same one used for the other tube... (note 6V6 heater-cathode rating: http://www.firebottle.com/ampage/td/vtd6v6.html)

 

[mikka]

Old radio techs around here didn't even bother with a resistor. (Though I think it's a good idea) They used to plug 5v heated rectifiers into 6.3v heater circuits and not give a toss. They said it shortened the life a little but so what........

 

[cannikin]

[quote author="mikka"] They used to plug 5v heated rectifiers into 6.3v heater circuits and not give a toss. They said it shortened the life a little but so what........[/quote]

really? Interesting

well fellas -- I guess the next thing is to give it a try -- I'll report back when it doesn't work, my voltages are funky, and I have a butt load of hum.

 

[cannikin]

Oh no one answered the other question -- Parallel rectifiers whats the deal with that.....?

never mind:

http://www.groupdiy.com/index.php?topic=151852&sid=b7b4ca183b5fc099629789d5666733f1

 

[Guest]

What is drawn will work well.

Don't worry.