How much filter can a 5Y3GT handdle?? 40uf???

richon · Post by **richon** » Thu 04/19/07 7:11 pm

i have my second 5E3 ready... and i have a 100Hz noise and i think it maybe is a filter (i have 3 X 16uF for the filters in my amp) making the B+ "dirty"

can i connect (paralel) to one of the filters another cap of 40uF (sorry i don't have any smaller right know) to test if the cap is doing his work right?????...

what could go wrong???

could the rectifier tube BLOW???

please help.

chris_deveau · Post by **chris_deveau** » Thu 04/19/07 7:21 pm

This sheet says 20uf:

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

What could happen with too high a value, is that the voltage could arc over the rectifier, and cause serious havoc on the other side. I asked a while back, and it was suggested that this could possibly kill the OT if everything wrong enough.

As i understand it, it is not guaranteed to happen, but you are rolling the dice if you try it.

I personally, would not do it, as i have had enough damaged bits in my amps without rolling any dice!

-chris

ontariomaximus · Post by **ontariomaximus** » Thu 04/19/07 7:24 pm

Measure the DC resistance of you secondary - there is safety margin there. With close to zero homes then 20uf would certainly be max. The winding resistance would be similar to a grid stopper.

s2 · Post by s2 » Thu 04/19/07 8:45 pm

I run them safely at 22uF. I've tried 32uF, but popped a nice Westinghouse NOS 5Y3GT. Rumor has it some of them can handle a lot more C than others, but it is a crap shoot.

If you are using a Sovtek 5Y3 (which isn't really a 5Y3 at all), you can use 32uF all day long and may be able to use 40 or 50uF (although I have not tried it myself).

richon · Post by **richon** » Thu 04/19/07 8:57 pm

i asked this because i want to know if it is safe to conect a parallel cap to the filters to know if one of them is not working right

cause i have 100hZ hum.. and i am guessing is a dirty B+

Fresh_Start · Post by **Fresh_Start** » Thu 04/19/07 10:11 pm

Some vintage Fenders (like 5F2-A) put two 16uf caps in parallel before the plates with a 5Y3. Should "look like" 32uf since they're parallel but something more may be at work in a power supply rail.

One thing to keep in mind about the Sovtek 5Y3's is that your B+ voltage will go up compared to a real/NOS 5Y3. About 20 volts in my Tweed Princeton.

Not a problem - just something you should know since you're troubleshooting.

Chip

richon · Post by **richon** » Fri 04/20/07 8:48 am

but is there a way to test each filter without turning the circuit apart????

any machine or technique?

Alexo · Post by **Alexo** » Fri 04/20/07 8:57 am

You could just unsolder one end of the old filter cap and solder in a new one alongside it?

richon · Post by **richon** » Sat 04/21/07 8:48 am

so it is... trial and error?

no other way than just unsolder one filter and test another cap in his position?

no other way to know if the cap is good or not?

there is no way to test the amp withoput it conected?

phsyconoodler · Post by **phsyconoodler** » Sat 04/21/07 9:43 am

Unsolder the negative end of the filter cap and measure for DC voltage at that end with the amp on.If you have any DC voltage the cap is no good.Remember,that filter caps are designed to pass AC and block DC.
you likely have another problem causing your noise.16uf is fine for 5E3's.And why do you say it's 100hz?

richon · Post by **richon** » Sat 04/21/07 10:21 pm

cause i hear the noise...

and i compare the noise to my "computer tone generator"... it is 100Hz...

i know for sure

a friend of mine told me it could be Ripple... from the rectifier tube ..

guess...i will have to keap on testing

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How much filter can a 5Y3GT handdle?? 40uf???

How much filter can a 5Y3GT handdle?? 40uf???