Forming Filter Caps in a JTM 45/100

Detailed assembly steps separated into threads.

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shakti
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Re: Forming Filter Caps in a JTM 45/100

Post by shakti » Thu Nov 25, 2010 7:09 am

In my black flag build, the RIFAs formed to less than 2V in just a few hours. Your results seem a little strange...based on my experience, I might suspect the BC/Vishay, but you never know. 5.7V is OK, but it should have been less in all that time...
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Re: Forming Filter Caps in a JTM 45/100

Post by Xplorer » Wed Oct 10, 2012 5:14 pm

it doesn't work for me, i wonder what i did wrong.
the voltage seems to be very high, over the acceptable 600v AC voltage that my volt meter can read... since more than galf an hour. i thought that the voltage would drop to 200v, 50v ... till under 5v.
all the volt meter says is : "1"
when i switch to the standbye mode, the volt meter starts to say 1700volts, 1400 .. 1300, then 450, 300 , 220 ... 50 , 20 , 10 ....

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Re: Forming Filter Caps in a JTM 45/100

Post by Xplorer » Thu Oct 11, 2012 6:40 am

ok, it's working now ;)
i got a new voltmeter cause the other one got fucked up, don't know why. now it decreased from 300v to about 27 volts... oscilating ...

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Re: Forming Filter Caps in a JTM 45/100

Post by rip » Wed May 03, 2017 1:31 pm

Found something here

http://www.valvewizard.co.uk/standby.html

Towards the bottom there's a mod describing adding a resistor parallel to the standby switch to leak some voltage to everything prior to turning the standby off. Prevents switch arcing...

Seems to me you could just put the 100K 2W resistor across the standby switch and leave it there...basically all you need to do to form the caps then is to pull tubes and flip the power on. Making sure the standby is on, sound off...

And then for normal use you have the benefit of equalizing the voltage across standby switch (no arcing)

Thoughts?

Rip

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Re: Forming Filter Caps in a JTM 45/100

Post by Roe » Thu May 04, 2017 12:58 pm

I'm using a 100+k power resistor myself. I've seend 45/100s with 600VDC across the switch. The problem is not only that the switch may fail but that you are putting stress on the choke
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Re: Forming Filter Caps in a JTM 45/100

Post by rip » Thu May 04, 2017 2:06 pm

Awesome...if you do it... I'm gonna to as well

Though...I may just put it on the main filter board

Thanks
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Re: Forming Filter Caps in a JTM 45/100

Post by Roe » Sat May 06, 2017 9:27 am

another advantage is that it eliminates any pop when you flip the standby switch.
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