Wayne, > Sounds like OM7ZZ's output was loaded too heavily, or that he had the > radio switched off when measured it, which would provide only leakage > current. OTOH he could have tripped F2, the self-resetting fuse for the > ACC output.
His load was a microHAM microKEYER II (setting everything for the trip). Unit is rated at 400 mA and will indicate a fault if the input drops below 11 volts. The rig and cables are on their way back to the DL group by now. > No load output: 13.1 VDC in all cases. > > Loaded output (500mA): very close to 12.0 VDC on all three units > tested. It should be a lot higher at the typical current required for > one relay (< 100 mA). 1.5 volts +/- at 500 mA is a bit much but it's not a big problem since MK II can use external power but it would have been nice to avoid yet another power supply for each station for the VP6DX group. It certainly should not be a problem for a single relay application. In the meantime, I'll take another look when my first K3 arrives (whenever that is <G>). 73, ... Joe, W4TV > -----Original Message----- > From: wayne burdick [mailto:[EMAIL PROTECTED] > Sent: Friday, December 21, 2007 1:32 PM > To: Joe Subich, W4TV > Cc: 'Elecraft Reflector' > Subject: Re: 12 VDC Output > > > Joe, > > We just measured the voltage at the 12V ACC output on three K3s. DC > into the K3 APP connector was 13.80 in all cases (measured at the APP > connector, K3 powered ON, in receive mode). > > No load output: 13.1 VDC in all cases. > > Loaded output (500mA): very close to 12.0 VDC on all three units > tested. It should be a lot higher at the typical current required for > one relay (< 100 mA). > > So the total drop at maximum rated load is about 1.8 V. Circuit drops > include two series protection diodes, two self-resetting fuses, and > the PMOS FET on/off switch (Q2). These should not be bypassed or > removed, as that would compromise the safety of the ACC output. > > You could replace D34 (1N4007) with a 1N5817/18/19 or SB520/530 to get > a few tenths of a volt lower drop if required. You could get another > couple of tenths by replacing both D6 and D34 with 95SQ015's, > although they're very expensive. > > Sounds like OM7ZZ's output was loaded too heavily, or that he had the > radio switched off when measured it, which would provide only leakage > current. OTOH he could have tripped F2, the self-resetting > fuse for the ACC output. > > 73, > Wayne > N6KR > > > What is the spec for the 12 VDC accessory output? OM7ZZ ran into > > some issues in interfacing with the K3 from the VP6DX group because > > the accessory output was only 10.8 volts even with a well regulated > > 13.8V supply to the transceiver. > > > > 10.8 would be marginal depending on cable resistance for a remote > > relay and is certainly too low for most of the commercial antenna > > switches that use 12 V relays. > > > > 73, > > > > ... Joe, W4TV > > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
