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5U4 Arcing - thoughts???

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#61
The thing is... using such rediculously high capacitor values fed from tube rectifiers is asking for troubles down the road.
It's just not good design practice, and not needed.
Perhaps a pi filter of 47uf, then-L/R,- then maybe 100uf is wiser.
But certainly no need for 1000+uf for a tube amp with two stinkin' PP outputs.

That designer was on drugs and thinking solid state in his tiny brain.
 
#62
i did a pp 6LU8 amps, i placed two 1000/450vdc caps, one per channel and the OPT b+ lead connected to it...

i design my tube amps so that each channel did not share common psu components like dropping resistors and caps, i provide them separately.....after the psu choke, they go separate ways...

caps are dirt cheap nowadays....

and if you know what you are doing, you can be rewarded...😎
 

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#74
Burnedfingers said:
I'm kind of curious here. You mentioned you re-capped it. Maybe someone already asked this but did you up the size of the power supply cap/s? Also, did it arc before you re-capped it? If you went too large on the filter caps I would guess that is your problem. Cary makes pretty good stuff and I just can't imagine an engineering problem on their end.
Click to expand...

Hi. It was arching before I replaced the caps. And I replaced everything with the exact same values for the caps...
 
#78
From here.
2-CV729/Su4 Rectifiers
Click to expand...
From here.
The CV729 is a pre-war design of full wave rectifier. The maximum rectified output is 175 mA. The minimum series resistance to prevent excessive current peaks is 100 Ohms. The commercial equivalent is the 5V4G.
Click to expand...
Yet from here, the rectifier is still listed as a CV729 but a contrary diagram has been added, shown below.
 

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#79
Hi. Yeah. That one confused me also - I had found similar information when looking for tubes... So, after doing research, I picked up some 5V4's and put in it. (a while ago) Then I came across some other information, contacted Cary to clarify and was told by them to go with the 5U4. Its, a mystery... There are also 2 versions of the SLI-50. The first, which is class A and needs to be biased. And the second, listed as Class AB and is auto biasing.
 
#80
Despite all the good discussion of details, the hard truth is that the Cary is poorly designed and you're going to have to fix it. I see this kind of thing from a lot of Internet gurus, and sometimes it bleeds into commercial products sold to unsuspecting buyers. But no amount of massaging can alter the ridiculously large power supply input cap. It needs to be fixed. Cary seems to have attempted some bandaids but refuses to see the problem. Ball's in your court.


All good fortune,
Chris
 
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