How do you replace audio amp on radioshack htx 202?

Answer 1

Common problem with the HTX-202 is that using it with a TNC requires the

volume be turned WAY up. With the squelch open it does not take long to

burn out the audio amp. There's an easy fix.

Open it up:

Remove the antenna, battery pack, and anything else you have hooked up to

the radio.

Remove 5 screws on the back and the 4 screws on the battery plate.

Pull the back away from the radio, taking care not to break the ribbon

cable that connects the to sides.

Find the audio sub board. This is on the main board just below the large

removable connector at the top of the radio.

Unplug this big wire connector from the top.

Flip the radio over and find the 6 pins for the audio sub board.

Break out the soldering iron and push the pins out from the back while

giving a pull on the board from the front. Be careful not to damage the

pins or get solder on any of the other parts. "that would be bad".

Now you have two options.

Option 1: Replace the entire audio board with another from a dead HTX-202

or an HTX-404. Option 2: Replace the IC on the audio board (IC601) with

an LM386N-3 LOW VOLTAGE AUDIO AMP.

Replace the audio board in it's place making very sure to only use just

enough solder to connect it, watch those connections, lots of other pads

on the back that are very close to the audio board's pins.

Plug in the wire connector.

Put it all back together.

:~) N5VJA

"To prevent this problem,

The HTX-202 requires a modification on the audio output board.

A 10 Ohms 1/4W resistor MUST be added in series with C603.

When output is loaded with way-too-high impedance load, The amplifier IC

is prone to high frequency oscillation (ultrasonic or higher).

If the IC start to oscillate, C603 apears to IC601 as a dead-short,

causing IC601 to blow.

A 10 Ohms resistor in series with C603 forms a dummy-load to prevent high

frequency oscillation.

Take your time! Unsoldering the audio PCB and IC601 can be tough if

you're not familiar with bouble-sided PCB and surface-mounted componants!