bigred,
check the bias on the driver and the final.
this will tell people a bit about what is going on here.
also, C179, a small blue roundish tantalum capacitor near the driver and final
tends to blow in these radios.
replace it with a 2.2uF 16 volt ELECTROLYTIC capacitor. watch polarity!
also check TR25, which is a 2SC1419 transistor bolted to the same wall as the driver and final, only further back.
this, and all other 2SC1419's should be replaced with 2N6487's or NTE152's.
there are 4 total.
one on the power supply board, and three on the main PC board.
TR25 is one of them, there is one mounted above the audio chip on that piece of aluminum, and one is on the far right side of the radio near the PLL chip.
it is mounted to that metal wall that encases the PLL section. (this one should be relocated by soldering wires in its holes and re-mounting it next to the one above the audio chip. the reason for this, is that this transistor causes the resistor behind it to get very hot, and thus causes those two crystals near it to drift in frequency. see that big resistor in the teflon "blanket"? it should be replaced with a 5watt 56ohm resistor that should be mounted to the bottom of the PC board, so it touches the metal of the chassis for heat dissapation) whew!
here is the procedure for checking the bias on the driver and final.
all you need is a multimeter to do this.
you can do it!
here ya go:
set your radio for channel 19, USB, and turn the mic gain all the way down.
find VR15 and test points (TP) 3 and 4.
test points 3 and 4 are little metal nubs that stick up from the board, and are attached by a short white wire.
TP3 is just behind L34
TP4 is just in front of L33.
remove the wire connecting the two test points.
set your multimeter to read milliamps on a scale that will read 0-100mA or so.
place one lead on TP3 and one lead on TP4.
key the mic. (i use a rubber band for this, as i dont have three hands.LOL)
if the meter swings backwards or reads negative; just switch the leads around.
now, adjust VR15 for 40mA.
replace the wire. you have just biased your driver.
repeat this procedure for the final by using TP1 and 2.
TP1 is just to the left of VR14, and TP2 is just behind C179 (that little blue cap i mentioned)
key the mic and adjust VR16 for 70mA.
replace the wire.
you have just biased your driver and final!
now, did you run into any funny numbers or numbers that wouldnt come up during this test?
tell us about it.
i would highly suggest that you start looking for a parts radio for this radio.
you will need it sooner or later.
LC
