The $30 lesson

 I'm sure you can guess what's coming based on the dollar amount in the title.

Today, to get started on my cross-band repeater, I needed to modify one of the UV-5R Baofeng radios to have a COR output.  This output, also known as COS, is a way to tell the repeater controller that a valid signal is being received and that the transmitter should be keyed.  Since this is a cross band system, both radios need to provide that signal.  This is going to require that I disassemble the radios, locate that signal, add a couple parts, and then put things back together.  Fortunately, another ham has already taken one of these apart and posted instruction.  So I got to follow in his footsteps.


Basically, the process is to remove the antenna, the volume knob, the battery, the round nuts securing the antenna jack and the volume control.  On the back, remove all the screws you can see.  You will need both a philips and a torx bit screw driver.  The torx bit I used was a T9.

With the screws removed, you need to separate the heatsink from the front of the radio.  I used a very small flat bladed screw driver and gently pried up starting in the middle of the bottom in the slot I found there.  I had to gently help it along by prying in various places on each side.  It finally came loose enough to remove.  At this point, the speaker which is mounted in the face of the radio will still be connected to the radio circuit board.  You can disconnect it or not.  It's up to you.  I left mine connected this time, but on the next one I will probably disconnect it.

The places I needed to access are on what would be the back side of the circuit board.  I didn't remember to take pictures of this part but I'll do my best to describe it.  As you're looking at the radio, you will see several philips screws scattered around the circuit board.  Those all need to be removed.  Here's the gotcha.  ** There are 3 screws under the LCD display that have to be removed to get the circuit board off the heatsink. **  This requires that the LCD display be removed.  This removal was not covered in the original instructions other than to say that it needed to be done.  And this is where the lesson comes in.

The LCD is held in place by two screw facing the bottom of the radio, which you should have already removed in the previous step.  On the opposite side, there are two tabs that bend over the edge of the circuit board.  I mistakenly believed that the display was connected with some sort of connector or contact device similar to what ICOM does or did with their displays.  I was *wrong*.  The display is actually soldered to the circuit board on one end.

 

This is a picture of the LCD connector, minus the LCD display where it connects to the circuit board.  I presume that this needs to be unsoldered prior to attempting to remove the display.  Based on my previous erroneous assumption, I broke the display from its connector when I was trying to remove it.  The $30 lesson learned.  So this radio is toast.  But I can still use it as a learning tool.  Doesn't make me any happier though.

So here is a picture of the whole circuit board.

 

The larger chip on the left is the CPU for the radio.  The chip on the right is the radio itself.  I have to go back to the original poster's instructions to find the chip that has the output I'm looking for, but both chips are identified there.

 

So there you have it, the $30 lesson.  At this point I'm going to fall back and regroup. As much as I want to do this project, I really can't afford to continue learning these types of lessons.

 

I'll keep you posted.

 

 

73
Steve
KDØWSW