Yes, I remember the smell of burning selenium rectifier very well!
I am going to use the relay to switch my open-line fed antenna to a "T"
configuration for 80m.
Incidentally, I love the Matchbox. There is nothing else like it. I
think it could easily handle 4 kW on CW and SSB.
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 22/04/2020 13:29, Rob Atkinson wrote:
If I remember correctly, some of the passive components around the
rectifier were intended to prevent the relay from hot switching. The
KW Matchbox was intended to be an EFJ accessory to the famous Desk
Kilowatt transmitter, a rig with a pair of 4-250s modulated by 810s.
When running 1 KW input you don't want the relay hot switching.
Most Matchbox owners today (I have two of them) remove those parts
because we do our sequencing in other ways. The selenium rectifiers
usually have a Vd of around 70 v. Even if you plan to power the relay
in the box as intended, I recommend replacing the S.R. with a common
silicon diode because they can be nasty when they fail and burn out.
They stink to high heaven and put out a toxic fume.
73
Rob
K5UJ
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