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- Thread starter TM86
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You'll need to replace the two unshielded wires on the supplied input cable with coax of some sort. Really needs to be a shielded lead. The tapoff point is TP1 in the original schematic. This would be the hot side of L20's 2-pin side. Don't connect to the 3-pin side of L20. You'll also need a 220-ohm resistor between the center wire of your tapoff cable and TP1. The input circuit of the PLJ will load down the signal and reduce the radio's transmit and receive performance if you just connect the wire directly to TP1 without the resistor in line. To avoid ground-loop buzz noises from the PLJ display circuits we use a .001uf disc cap between the tapoff cable's shield and the ground side of L20. This breaks any DC circuit current that could add noises to the receiver and still passes the desired RF current to the counter.
The voltage regulator on the PLJ circuit board tends to overheat if you power it from a voltage much above 10 or 11 Volts. We adopted the habit of using a TO-220 3-terminal regulator like the 7808T to power the PLJ in a radio. The tab solders to a suitably-large ground foil. Black wire to the PLJ power socket goes to the center pin, the red positive wire to the right-hand pin. The left-hand pin is the regulator's input and goes to the positive side of the big electrolytic filter cap. This pic is not from a 148, but it conveys the idea.
Have fun and 73
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It's not quite as simple as "change a crystal" like some radios. The commercial "EXPO 100" channel-expansion kits for this type radio contained an oscillator circuit along with the quartz crystal. It would "force feed" a mixing frequency into the 29's PLL circuit and cause it to lock onto either upper or lower channels. The crystal you would need for this trick will be around 16.36 MHz. Easy way would be to obtain a EXPO 100 type "A" expansion kit and change a crystal to about 16.360 MHz. If you can sweet-talk the owner of an old Browning Mark 3 SSB transmitter into it, plucking out the channel 9 transmit crystal from that transmitter would do the trick. Can't imagine a base-station owner having any need for a channel 9 transmit crystal.
Then all you'll need is an Arduino board and software to make it a CW keyer.
73
The XYL wishes I wouldn't.Wish I could find those sales and deals....
Nevermind, got the D60 working. Bad C175, which I replaced with an apparently just as bad cap. Replaced again and it's at least receiving. May have to wire up a mic for TX testing as I don't think I've got one set up for this radio.
But, yeah, as of today no "dead" radios from this haul.
If I say anything more about any of the others, it will be in separate threads. Probably better not to mix nightmares.