champ filter caps &nbs

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yellatele88
Senior tube assistant
Posts: 141
(5/21/05 2:18 pm)
Reply  champ filter caps
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 I have been looking around at some of the parts I have, and I wanted to build a 5f1type champ with my inventory.

I noticed that the 5f1 calls for a 16uf 450V and 2 8uf 450V caps. I have a whole bunch of 22uF 450V caps. Can I use them instead? I would imagine that I would just get better filtering with my caps.

Thanks

Bob
 
wayneosdias
I will work on all amps
Posts: 374
(5/21/05 3:20 pm)
Reply  yes
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 Ya you can use them, I think the issue is if your gonna use the 5y3 recto, which will want a max of 20uf at the first node. Ive seen this asked before and the concensus was that the 5y will handle 22u fine. If you going ss you can filter it all you want.

wayne
 
phsyconoodler
I will work on all amps
Posts: 382
(5/21/05 6:35 pm)
Reply  Re: yes
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 Actually the first filter cap can be up to 33uf with a 5Y3 rectifier. 22uf will work fine. 33uf is the max for a 5Y3 and some people even use more and get away with it.
I built a Deluxe with a 30mf filter cap and it worked fine and is still working fine after a year.
 
yellatele88
Senior tube assistant
Posts: 142
(5/21/05 7:31 pm)
Reply  how do you find out
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 Thanks for the info.

Just out of curiosity, how do you find out how big of a cap a rectifier can handle? The data sheets I have don't seem to list that spec.

Thanks
 
wayneosdias
I will work on all amps
Posts: 375
(5/22/05 2:04 am)
Reply  tdsl
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 Here

tdsl.duncanamps.com/tubesearch.php

wayne
 
yellatele88
Senior tube assistant
Posts: 143
(5/22/05 8:28 am)
Reply  Re: tdsl
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 Psycho,

Pleae pardon my ignorance, but is 33uF the max for the first filter in the stage, or is it the max for the entire filter section? I've used a 5y3 in an amp that had a total of 88uF in the filter stage, and it didn't seem to have any issues - I just didn't prefer the tone, so I went to a 5v4.

Bob  
 
GroundhogKen
Moderator
Posts: 2779
(5/22/05 8:51 am)
Reply  Re: tdsl
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 33uF is the maximum for the first smoothing cap that the 5Y3 sees. Any caps that are further down the power rail don't matter.

I ran 5y3s into a 47uF for quite a while without issue--no arcing, no tube failure. I ended up changing to 33uF to add a little sponginess.

Single ended amps like Champs are more prone to hum than push-pull, so increasing the filtering a bit over the vintage values is a good idea.

If you live in a region where the mains frequency is 50Hz, increasing the filtering of single ended amps becomes almost manditory--especially at the B+ node and the screen supply.


Ken
 
Rebel Leader
Junior tube assistant
Posts: 72
(5/23/05 10:13 am)
Reply  Re: tdsl
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 What is the factor that limits the amount of capacitance that
a tube rectifier can drive? Is it related to surge current at
startup when the 1st filter cap is discharged?

What is the failure mode if you use a large, say a 100uF cap,
filter capacitor for the first stage on a 5Y3 FW rectifier?


Cheers,

Rob
 
HotBluePlates
I only work on Fender's
Posts: 1189
(5/24/05 7:36 am)
Reply  Re: tdsl
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 You got it, surge current when charging that first cap on startup.

The other caps don't matter, because they're separated by either a dropping resistor or a choke which limits the current surge to charge them.
 
punkykatt
Junior tube assistant
Posts: 92
(5/24/05 8:14 pm)
Reply  Re: tdsl
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 I read somewhere that if you turn the power switch on for a few minutes, shut it back off , put the standby to play, and turn the power back on, it will have mercy on the rectifier. What do you think? Hogwash???? I think i was a Semour Duncan amp website.
 
 
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