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Old 27th May 2012, 06:44 PM   #1
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Default B+ delay for DHT amp

Hi All

I'm building a DHT amp, I intend to use 5u4-g for B+, but I want to delay B+ 30-40 seconds, what is the best method?

Center tap switch ?
Delay circuit like this RUBLI HTR-214
Or sepperat transformer for heater ?

Best Regards
Fonnesbek
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Old 27th May 2012, 07:07 PM   #2
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Use an indirectly heated rectifier instead of the 5U4 and you have slow B+ start built in

Thomas
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Old 27th May 2012, 07:24 PM   #3
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yes but indirect heated rectifiers are harder to find and more expensive

Fonnesbek

Last edited by fonnesbek; 27th May 2012 at 07:40 PM.
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Old 27th May 2012, 07:59 PM   #4
popilin is offline popilin  Argentina
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Try this

My First Power Supply
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Old 27th May 2012, 08:25 PM   #5
euro21 is offline euro21  Hungary
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Quote:
Originally Posted by fonnesbek View Post
yes but indirect heated rectifiers are harder to find and more expensive
Why?
NOS russian rectifiers, for example 5C4S, are cheap and accessible.

5c4s rectifier | eBay
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Old 27th May 2012, 08:34 PM   #6
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Quote:
Originally Posted by fonnesbek View Post
yes but indirect heated rectifiers are harder to find and more expensive
Nothing beats TV damper tubes. Only drawback, you need two of them. Just bought a bunch of 6DQ4s for 35 cents each.

Thomas
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Old 27th May 2012, 09:31 PM   #7
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To have a perfect onset of B+ exactly 40s after startup you need a separate timer board. You can build it or you can buy it.
eBay Italia - Aste online e shopping a prezzo fisso

I use this in my project. It works very well and the delay is selectable via a pot. also you can switch between seconds and minutes (by setting a jumper).
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Old 28th May 2012, 05:58 AM   #8
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Nice. Thanks!
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Old 28th May 2012, 09:02 PM   #9
djn is offline djn  United States
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A pair of 6D22S half wave diode tubes work great as they take 36 seconds to warm up. Cheap as well.
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Old 28th May 2012, 11:53 PM   #10
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Quote:
Originally Posted by fonnesbek View Post
Hi All

I'm building a DHT amp, I intend to use 5u4-g for B+, but I want to delay B+ 30-40 seconds, what is the best method?

Center tap switch ?
Delay circuit like this RUBLI HTR-214
Or sepperat transformer for heater ?

Best Regards
Fonnesbek
I like a 30 seconds delay for the ''power on'' in rush. The 6C33 warm-up time is 600 seconds, after it the tube is OK to receive the HV B+, 600 seconds is a bit longer to a delay circuit or clock.
Iam negatively surprised with all commercial tube amps builders, nobody use two power switches, only Atma-Sphere use it.

A power on switch cost around 0.25 dollar in China, an delay circuit is much more expensive and need more hand work.
I like plain simple solutions, they are hard to fail.
There is any reason why all these brands do not use two power on switches Iam unaware?? in favor of more complicated delay circuits.
Regards
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Last edited by FullRangeMan; 28th May 2012 at 11:57 PM.
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