Border Patrol Power Supply

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kmtang

I read an article regarding the Border Patrol's Power Supply which can be used for PP and SE amps.

http://www.borderpatrol.co.uk/psurev2.htm

If I understand it correctly, it employs choke input filtering with 220uF capacitor at the output.

With this configuration, the ripple at the output would be very high which is not good for SE amps at all. I also tried using PSU simulate the result with different loading to the choke input power supply. It became very unstable when the current draw is low.

I think I would just stay with the simple CLC filtering with use of large H low resistance choke which would get me the best result.

Johnny

DSP_Geek

kmtang said:
I read an article regarding the Border Patrol's Power Supply which can be used for PP and SE amps.

http://www.borderpatrol.co.uk/psurev2.htm

[...]
Johnny

Look carefully at the second diagram in the schematic:
http://www.borderpatrol.co.uk/images/S800.pdf

The line surrounds the BP power supply, which contains no capacitor. It depends on the existing cap in the amplifier. You're correct that low currents on a choke-input power supply are sub-optimal, but consider the schematic again: the BP box also includes a hefty bleeder resistor, which I would assume is sized to maintain current above the critical value.

Interesting retrofit concept; wish I'd thought of it.

Francois.

Eli Duttman

Keep the theory of choke I/P filtration firmly in mind. For "proper" operation, a minimum current known as the critical current MUST be drawn. An excellent approx. to the critical current, in mA., is given by V/L. Many choke I/P designs include a bleeder resistor to ensure the critical current gets drawn. FWIW, 10 KOhms is the value appropriate for use with a 10 H. inductor.

While the low O/P voltage is a negative, choke I/P filtration has definite plusses. The O/P voltage is quite stable up to the current limit of the supply. The ripple waveform in a choke I/P filter is a fair approx. of a sine wave, unlike the highly triangular waveform found in cap. I/P filters. Guess which sounds better.

BTW, it's not very difficult to build an EXCELLENT choke I/P filtered PSU with SS diodes. Solid state or hollow state, sweating the details is important.

have'

question

The BP can deliver 300_390_430V at 250mA (of 350mA.)
Which value do we need for the choke ?

kmtang

Surely bigger H is better. I would say you need at leaset 10H for choke input filter.

It is very important that a bleeding resistor is used so that it takes the minimum loading to get the Power Supply into linear region. You may refer the datasheet of the rectifier tube for detailed information.

Johnny

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