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Lifting centre tap for B+ delay
Lifting centre tap for B+ delay
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Old 16th September 2020, 09:20 PM   #11
6A3sUMMER is offline 6A3sUMMER  United States
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He said: "(About 370v DC across it in standby)"
It = 10k 10 Watt.
I took him Literally.
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Old 17th September 2020, 08:59 AM   #12
Ketje is offline Ketje  Belgium
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Quote:
Originally Posted by 6A3sUMMER View Post
He said: "(About 370v DC across it in standby)"
It = 10k 10 Watt.
I took him Literally.
Well, he is right, at open circuit that is
Mona
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Old 18th September 2020, 04:54 AM   #13
petertub is offline petertub  Sweden
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Lifting centre tap for B+ delay
Quote:
Originally Posted by hariadi88 View Post
Hi,

If I have power trans with full wave rectifier, is it possible (and safe) to put switch between centre tap of secondary and ground to delay the B+?

I know ther is more proper B+ delay circuit out there, but I prefer the simplest one (albeit manual).
Any simpler way? Use Thermistor instead of switch?

Thanks in advance
Delaying B+ is overrated and might be damaging to the power tubes.
What do you want to solve with this ?
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Old 18th September 2020, 06:23 AM   #14
hariadi88 is offline hariadi88  Australia
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Hi,
I saw the voltage at turn on goes up to 500V and settles down to 400V at the first cap (as intended) in 30 seconds or so. That exceed the capacitor rating of 450V, and I don't have higher rating capacitor.
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Old 18th September 2020, 08:53 AM   #15
6A3sUMMER is offline 6A3sUMMER  United States
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Get capacitors that are rated for 500V or more.
Some are rated for 550V surge and 500V operational.

You may have to stack capacitors in series, with leakage balancing resistors across each one. You need 2X the capacitance for each one.

Keep in mind, if the output tubes ever die, the B+ will rise to 500V, just like they do at start up.
To quote the capacitor . . . Ouch!

And ask yourself, what happens if you, or someone else forgets to put the standby switch in standby before powering on the amp?

Last edited by 6A3sUMMER; 18th September 2020 at 08:55 AM.
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