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miliamps
- Thread starter donemad
- Start date
Assuming you have the manual, put the meter IN SERIES with the specified lead or test point and adjust the specified control.
If you don't have the manual, get it.
If you don't have the manual, get it.
the driver and final transistors are located on the back wall of the chassis, towards the left side.
the driver (TR39) is usually a 2SC2166, but it could be a 2SC1306 depending on the age of the radio.
the final (TR41) is usually a 2SC1969.
the NTE152 will not work as a replacement for either of those transistors.
it is a replacement for the AM regulator transistor (TR34) which is located on the right wall of the chassis to the rear of the audio IC chip.
the stock part is usually a 1419 or a 1135.
the NTE152 will work as a replacement for this transistor.
to set the bias on the driver and final transistors; put the radio in either USB or LSB mode and turn the mic gain all the way down.
set your multimeter to mA (milliamps).
start with the driver.
remove the wire labeled TP8 from its pin. put one lead of the multimeter on the pin and the other lead on the wire, and key the mic.
if the mA reading is negative, switch the leads of the multimeter.
adjust VR8 for 25mA.
now do the final bias.
put the wire labeled TP8 back on its pin and pull the wire labeled TP7 off of its pin. put the multimeter inline just like you did with the driver, key the mic and set VR9 for 50mA.
put the wire back on its pin and you are done!
good luck,
LC
the driver (TR39) is usually a 2SC2166, but it could be a 2SC1306 depending on the age of the radio.
the final (TR41) is usually a 2SC1969.
the NTE152 will not work as a replacement for either of those transistors.
it is a replacement for the AM regulator transistor (TR34) which is located on the right wall of the chassis to the rear of the audio IC chip.
the stock part is usually a 1419 or a 1135.
the NTE152 will work as a replacement for this transistor.
to set the bias on the driver and final transistors; put the radio in either USB or LSB mode and turn the mic gain all the way down.
set your multimeter to mA (milliamps).
start with the driver.
remove the wire labeled TP8 from its pin. put one lead of the multimeter on the pin and the other lead on the wire, and key the mic.
if the mA reading is negative, switch the leads of the multimeter.
adjust VR8 for 25mA.
now do the final bias.
put the wire labeled TP8 back on its pin and pull the wire labeled TP7 off of its pin. put the multimeter inline just like you did with the driver, key the mic and set VR9 for 50mA.
put the wire back on its pin and you are done!
good luck,
LC
VR6 is your AM carrier control.
dont turn it up past a 5 watt deadkey.
if you are keying 3 watts, your final is ok.
you need to re-tune the radio now that you have replaced some parts.
set the radio to AM mode, channel 20, turn the DYNAMIKE control all the way up, key the mic, and using only a plastic tuning tool that fits the slot in the slug in the coils;tune L26,L27,L28,L29, and L36 for max RMS wattage on your wattmeter while saying "ahhh" into the mic in a steady tone.
dont mess with L39. its a harmonic filter and if you mess with it, you will create harmonics in your output signal.
if you just key the mic and tune the coils for max deadkey, you will have no room for the transmitter to swing upwards with modulation.
here is a link to an alignment for your chassis:
The Defpom PC-385 Alignment Page
here is a link to some mods for your chassis, courtesy of DTBradio:
CB Tips and Tricks
good luck with it,
LC
dont turn it up past a 5 watt deadkey.
if you are keying 3 watts, your final is ok.
you need to re-tune the radio now that you have replaced some parts.
set the radio to AM mode, channel 20, turn the DYNAMIKE control all the way up, key the mic, and using only a plastic tuning tool that fits the slot in the slug in the coils;tune L26,L27,L28,L29, and L36 for max RMS wattage on your wattmeter while saying "ahhh" into the mic in a steady tone.
dont mess with L39. its a harmonic filter and if you mess with it, you will create harmonics in your output signal.
if you just key the mic and tune the coils for max deadkey, you will have no room for the transmitter to swing upwards with modulation.
here is a link to an alignment for your chassis:
The Defpom PC-385 Alignment Page
here is a link to some mods for your chassis, courtesy of DTBradio:
CB Tips and Tricks
good luck with it,
LC
you said you replaced the "finals".
give us some detail about exactly what you did.
what parts did you replace? what parts did you replace them with? etc...
the more details you give the more we can help you.
LC
give us some detail about exactly what you did.
what parts did you replace? what parts did you replace them with? etc...
the more details you give the more we can help you.
LC
