Supertune: Replace the stock final with a 2SC1969 unit.
Use CARE when soldering to the PLL chip! If desired, this mod may be wired through a switch. The smaller the value, the more the receive is boosted.
Install a 22k-220k ohm resistor between these two points. Receive Boost: Locate pin 14 of the PLL chip, and the Positive (+) side of C-12. You can also try removing R125 and increasing the value of R102. For AMC changes, place 5k variable resistor from base of TR33 to ground. RemoveC119, and run a 1000uf cap from negative side of C119's position to the base of TR34, with the positive side of the 1000uf cap going to the base of TR34. However, there are a few mods that will yield better over-all PEP and still keep decent quality sound. I have found that the best over-all sound and performance comes with nothing more than a standard tune-up, with the AMC circuit left intact. I do not recommend extensively modifying the 140/142, due to the type of modulation circuit used. Supertune: Many of you have asked about supertunes for these radio. You may need to re-align the frequencies a bit. Wire a switch from Pin 10 to ground(SW-2 on the chart), and another from pin 11 to pin 12 (SW-1 on chart). Isolate pin 10 from ground (Cut the trace). Locate the MB8719 chip (usually right behind the channel selector). Reset the AMC level for 100% modulation.Įxtra Channels: Replace the 11.1125 mhz crystal with a 11.3258 crystal. RemoveC174, and run a 1000uf cap from negative side of C174's position to the base of TR41, with the positive side of the 1000uf cap going to the base of TR41.
I have found that the best over-all sound and performance comes with nothing more than a standard tune-up, with the mod level set for 100%.
I do not recommend modifying the 148 very much, due to the type of modulation circuit used. Supertune: Many of you have asked about supertunes for this radio. Wire a single-pole, single-throw switch from pin 10 to ground (SW-2 on chart), and another from pin 11 to pin 12 (SW-1 on chart). For safest operation, do not jumper any diodes.Įxtra Channels: Locate the MB8719 chip (usually right behind the channel selector).
This does increase the output by a small amount, but it also causes a risk of extreme receive distortion when receiving high signal levels at high volumes, as well as a slight risk of component damage in the event of an overly-high inductive kickback voltage spike. Note: Some tips mention jumpering a diode with a piece of wire. They are the result of my own experience and research. Note: These are NOT copied from any other source.
Watch for new content as I get time to update this page. Most of these will be categorized by radio brand and model, plus a category for miscellaneous tips.