Modifications for the ICOM - RogerK

1. You're completely successful.2. You screw up a surface mount pad, but the radio still works when you're done.3. You're a total hack using the wrong tools, and you send the radio back to Icom for repair.Hopefully, you're a result 1 type person. At worst, you're a result 2. If you think your going to be a result 3 type, don't evenstart. Call a friend.We've done this mod on 2 radios with complete success. We can't guarantee that in later radios this mod will still work. It worksat least with serial numbers up to 1111 in the last 4 digits.Let's get started!Remove the 8 screws that attach the cover, and remove the top cover of the radio.Orient the radio so that serial, power and RF connector are closest to you, and the power switch faces away from you.On the PC board closest to you, in the upper left hand corner you should see a 80 pin surface mount chip. It has a number suchas 64F3334 stamped on it. This is the processor.Near the upper left hand corner of the chip, you should see 2 small green 0-ohm resistors. To the left of the two resistors youshould see an unpopulated pair of pads. These are the 3 "R"s below, on the left. The 4th "R" is used for location reference below.| RRR R| o ooo| o -----------------| o | || o | | D| | | D| r | || -------------------|| --| | || | || | || -----------------------(Picture courtesy of Alan Adamson, NE1H)Using the soldering iron and knife, *carefully* remove the right hand resistor. You'll need to alternately heat the two ends, whileapply a *light* pressure with the knife. Once it's hot enough, it will left off. It's very easy to destroy the pads the resistor issoldered to, so be *careful*.You'll now need to short the pads of the left resistor (this is the unpopulated one). You can either try and re-use the resistor youjust lifted (least good idea), short them with a short piece of wire wrap wire (OK idea), or use a real 0-ohm resistor (best idea).For the next step you have two options. One option is easy and does not require removing the board from the radio(recommended). The other option is "more correct", but will require disconnecting all the cables, removing the 5 screws thathold the board down, etc (purist method). We'll presume you're more likely to want easy, so here are the steps for it.Keeping the radio oriented as described above, look below the right hand resistor (the one we removed). You should see 3 vias(holes) (see picture above). Follow the left most via, and it should go to the left most pin of the processor. The second via shouldgo to the next pin to right, and third via should go to the pin to right. At this point, you should see two pins that don't appear tobe connected to anything, then a pin that connects to a small black resistor marked 201 (this is the 4th "R" in the picture).If you've sucessfully located the 6 pins above, we want to short the pin that is the 4th from the left to ground. Above these 6pins, you should see a small black rectangle, with 8 pins. I believe it is marked 220. On the side of this part (it's a resistor pack),there is a pin that is soldered to the ground plane.To short the 4th pin from the left to ground, tack a wire to the pin. Be *very* careful not to short the adjacent pins to the 4thpin. It's very easy to do. It you do, use a piece of Solderwick or coax braid to remove the solder. Better yet, don't short the pins.Tack the other end of the wire to the pin on the resistor pack described above.OK, you'd rather do it the "more correct" way. Disconnect all the cables from the board. You'll need to remove the shield fromthe RF section to remove the white ribbon cables. Disconnect the power and speaker cable. Remove the 5 screws that hold thePC card down. Remove the card from the radio.Orient the board as described above. Look for the white connector above the packet connector (lower left). It's marked J12. Justabove that are a pair of solder pads for a resistor. One side goes to ground, the other goes to a via. Follow the trace on thebottom side of the board. You should see that it goes to a via, but that the trace has been cut right next to the via.