The AM Forum

Hi Folks,


I have a DX-100 with what looks like a 3PDT PTT relay. I don't know the coil voltage the only marking on it is 33AC64C. Before I put any voltage to it, I measured the DC resistance and I am getting 1.5 ohms. It seems really low to me based on a couple of other relays I measured (15 ohms for a 6V and a 120V with kohms of DC resistance). I know it's not a lot of info but any idea if the coil is shorted at 1.5 ohms of resistance or is it possible to be this low?

Thanks
Kevin KD1NW

As wired into the DX-100, how much voltage should appear across the coil?

Hi Pete,

The coil isn't wired like usually seen, for example half wave rectified off the filament supply. One pole of the relay coil is grounded the other pole of the coil is wired to pin 1 of the external octal connector. I assume that voltage was applied at pin 1 to energize the coil. Additionally, the connection to pin 1 of the octal only goes to the relay coil and is not connected to the plate switch as seen in the schematic

Thanks
Kevin

Either the coil is shorted or it's an AC coil probably 6 volt or less.  Would not be a DC coil with that low amount of resistance.  Make sure your ohm meter is accurate.

Thanks Fred

This goes back a few years, but my DX-100 didn't have an internal relay.

My setup was a 120vac feed from the receiver standby/operate switch to a DowKey coaxial antenna relay with external contacts that shorted two of the octal socket pins on the DX-100.

This ensured that the coax relay was activated before the B+.


Don W4DNR.

Thanks for the info Don. It's possible this radio was use din a similar way

As already mentioned, Might have been looking for 2.5 to 6.3 vac off that octal. Ty 6.3 vac for a couple of seconds, if not shorted relay will latch.  Then if no smoke leave it on a few minutes and see if it gets hotter than just slightly warm.  --you know, fun stuff.

What exactly do the switched poles connect to and are all used? Could be easily replaced if shorted, of course.

HI Rick,

I'm sorry I missed your post. Only today I got around to confirming that it is a 6 volt relay. The relay is PTT, It controls screen for the 1625 and 6146 and the vfo operation. I traced the pins on the octal and they are custom wired. The only one that is according to the schematic is Pin 8 to ground. Anyway, Pin1 goes to one side of the relay coil, Pin 3 gets 6VAC off of the 6AQ5 clamp tube.  You leave the plate switch on and connect 1 and 3 to fire the ptt and create output. Unfortunately, the 110VAC on pins 2 and 4 does not switch on and off the way the radio is wired so it won't control a T/R relay the way it is. Pin 7 is weird in that it runs to the crystal / vfo switch, along with one of the SO-239. Not sure why they both connect there. There is no crystal holder so I assume someone was using an external VFO. Pins 5 and 6 run up to the 1625 area and end on a terminal strip not connected to anything ( I assumed they would be used for the 500 ohm audio output option). So now, I just need to figure out how to control the 110 on the octal so I can control a T/R relay. Once I get that working maybe I can run audio in on pins 5 and 6 to drive the grids of the 1625 instead of mic audio, not sure. Like you said, fun stuff!

Thanks 73
Kevin