Power Supply Dummy Load

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M0XXQ
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Power Supply Dummy Load

Unread post by M0XXQ »

I have a Manson/Palstar/Sharmans EP-925 20amp PSU with a suspected over voltage fault which is intermittent so rather than test a £1200 SSB transceiver I bought a 1ohm 200W power resistor and mounted it on some timber and added a lead for connection to the PSU under test.
Simple but effective, draw around 14amp and the fan keeps the resistor cool for long soak tests - so far not been able to replicate the fault on the PSU! :mrgreen:
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VU2NAN
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Re: Power Supply Dummy Load

Unread post by VU2NAN »

Nice job, OM Robert!

Here's my quickfix for testing a linear PSU.

https://nandustips.blogspot.com/2013/01 ... ckfix.html

73,

Nandu.
M0XXQ
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Re: Power Supply Dummy Load

Unread post by M0XXQ »

Hi Nandu, that is a very neat idea thank you for sharing :)

73

Rob.
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VU2NAN
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Re: Power Supply Dummy Load

Unread post by VU2NAN »

:)
M0XXQ
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Re: Power Supply Dummy Load

Unread post by M0XXQ »

Ok well after a full hour of load testing the fault appeared and 17V appeared at the output, followed by the full 24V at the output - failing 2N3055 pass transistor, stripped the PSU down and located the faulty device with a DVM and sure enough 76Ohms between the collector and base in both directions and the collector and emitter gave a low-ish reading.
I will build a crowbar circuit into this PSU as it has no protection for over-voltage.

I shall run it under load at around 13 amps for a good hour to make sure the fault has cleared.
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VU2NAN
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Re: Power Supply Dummy Load

Unread post by VU2NAN »

That's systematic trouble-shooting and making a system fail-safe, OM Rob!

73,

Nandu.
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