Intermediate transmitter problem with the HTX-202.
Mon Jul 31, 2000

- kb8zcj@amsat.org


[*] Disclaimer. (rant rant rant)

   Performing any actions described in this text WILL void your Radio
   Shack Extended warranty. If you damage your radio in any way while
   performing these actions, you are entirely at fault.
   If you were like me, you would use this as LAST RESORT.
   Also, I am 17 years old, you could call me insane for doing such
   a thing. But it worked :)

[*] Description of the problem and other junk.

   I had an intermediate problem with my HTX-202 where when
   transmitting, the TX indicator would come on, but power meter on the
   bottom of the LCD display would not light at all.
   I didn't know at first if this was an indicator problem or a
   transmitter problem so I switched the radio to a simplex frequency
   and tested with a handheld scanner. The signal was very weak so I
   knew the radio was not transmitting properly and I was probably
   receiving whatever was radiated from the exciter circuitry.
   I had the way-too-expensive extended warranty on it so I sent the
   radio in for repair, only to wait a whole month for it to come back
   in the same condition with the same problem.
   Unsatisfied with the way it was repaired I took it into the store and
   had it replaced with a brand new one free of charge.
   After about a year, the new one developed the exact same problem!

[*] So what was wrong?

   I started asking around on local repeaters and everyone who owned
   an HTX-202 said they where excellent radios and they had never had
   any kind of problem with it. They also had no idea what was wrong
   with my radio. So I got on the Internet, checked the QRZ website and
   many other sites to see if anyone else had the same problem I did.
   I found no information about the problem, and I knew that if I called
   Radio Shmuck, they would just tell me to send it in for repair.
   I finally found out what possibly could be wrong. A guy from the 4
   region who claimed to be a repair tech who worked on the 202's said
   it was a common problem, and we talked on a phone for about an hour
   as he explained that it was a loose connection to the antenna caused
   by stress on the BNC connector. I told him the connection was fine
   and he went on to say it could be a grounding problem.
   Not enough ground it was! I decided to go overboard with the
   grounding and do some crazy soldering :)

[*] What to ground, and how to fix this !@)%*!@% radio !!

   So here it is, I just kinda guessed and put a bunch of solder blobs
   everywhere, put it back together and it works like a charm now.
   I hope you have the same bit of luck!

Taking it apart ...
1. If you have a belt clip, remove it by unscrewing the two screws which
   bind it to the back plate.
2. On the back plate, you should see five screws. One should be in each
   corner and one in the center.
3. Remove the center screw, and then carefully remove the screws on the
   corners. These screws are very delicate and strip very easily so
   be very very carefull, especially when putting the radio back
   together. My radio is currently held together with only two of the
   corner screws and some electrical tape :)
4. Remove the back plate carefully. You may have to use a screw driver
   to slowly pry it off.

   Now it's time to look around the PCB. You'll see mostly surface mount
   resistors, capacitors, and a few Motorola integrated circuits.
   In the bottom right hand corner of the PCB, with the knobs facing
   away from your body, you should see a four-lead transistor surface
   mounted to the PCB. (It looks like a tiny hockey puck.)
   The female BNC jack should be soldered to the PCB in three points,
   the two on each side being ground, and the center being the tip.
   Also in the center of the PCB, you'll see a hole with threads in it.
   This is where the center screw is SUPPOST to ground the PCB to the
   back plate.
   Also on the right hand side of the PCB where it is soldered to the
   metal casing you'll see a little metal tension grid thing, this is 
   also where the PCB is suppost to be grounded.
   In all these cases, the ground is not good enough!
   So here's what to do to fix this.

1. Apply some more solder to the center blob where the antenna jack's
   tip connects to the board. You will know it is the right one becuase
   it will always be in the center between the two ground blobs, and 
   there will be a 'U' shaped cut in the PCB. (very strange eh?).

2. Bridge solder from the right blob of the antenna jack to the metal
   casing which is soldered to the PCB.

3. Apply some solder around that hole in the center of the PCB so you
   have a nice even blob about 2mm in height.

4. Remember that transistor? I think its the pre-final transistor but
   I have long lost the schematic so I am unsure.
   Lucky us, the lead closest to the metal casing is our ground lead.
   Make a solder bridge from this lead to the metal casing as well.

5. Check the connections with a metal pick to make sure they aren't
   loose or anything. The last thing you need is a good shockwave
   caused by dropping or bumping the radio to cause these solder blobs
   to come loose and send them into oblivion to short out god knows
   what.

6. Now get your back plate and use a hand grinder or something to 
   remove some of the gunk and oxidation from the inner side. Proper
   grounding to the back plate is very important.

7. Carefully put everything back together.

[*] End rants.

   This should hopefully solve the problem. When I put my HTX-202 back
   together I was pretty much playing russian roulette as I depressed
   the PTT button. I jumped on a repeater right away as soon as I saw
   it was transmitting to see if I was heard. I got an immediate reply
   and was suprised to have fixed my first radio simply by guessing
   around and getting down and dirty with a soldering iron.

   Have fun, and remember: DO THIS AS LAST RESORT, LIKE I DID. :)

- kb8zcj@amsat.org