The R2213 resistor in the Yaesu FT-840 is the one design flaw which will eventually take your rig down.
The existing resistor is 3w and it gets SUPER hot and starts burning the board. Eventually it will blow up and take nearby parts with it. Maybe the whole board. So the fix is simple.. replace it before it becomes a problem. The new resistor is 30w and anchored to the case so it displaces the heat. Now the case gets warm in that area but no where near hot. I cant imagine how hot that part was inside the case.
The part is a 4 dollar resistor and the repair is pretty easy to do. I have two FT-840s and I love them both. Whatever I can do to prolong the life of these rigs is good for me.
First things first.
Where I was told by 2 others to get the part was here.
http://www.digikey.com/
What you are looking for is
Bourns P/N PWR221T-30-8R20F for $3.23
On the digikey page I entered "PWR221T-30-8R20F" as the part number.
and came up with this page.
http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=PWR221T-30-8R20F
What that is, is a 8.2 Ohm 30W Power Resistor. The hole on the top of it is designed to be bolted to a metal case or heat sink to dissipate the heat.Afer you install this on the back of the case it will get warm but it will NOT be too hot to the touch. This part takes the heat off the board and uses the case of the rig as a heatsink.
That is the part on my desk ready for the installation.
On to the replacement task.
The first step is to remove the covers.
1. The Top Cover comes off first. Make sure you mark down on a piece of paper exactly where the screws go. They are really easy to strip out and the ones on the sides are 2 different sizes. If you put them back in your will strip the holes out. When you remove the 5 screws (four on the sides and one in the back) The top cover is ready to come off. Take it off gently because there is a connector connected to the internal speaker still under the case. Make sure you disconnect the speaker connector and set the top cover on the side.
2. The bottom cover. There are various screws on the bottom those are the only screws to remove. Make sure to mark where those screws go as well. They seem to all be the same size but it is always safer to put them right back where they came from.
3. At this point the radio should look like this.
The R2213 Resistor is in the bottom left of the picture
Here is a close up with a light below the part.
Underneath the board you will see it stamped R2213. The white cylinder is the resistor in question.
I have two of these rigs and they were both mounted differently from each other.
I measured resistance across the resistor and found they BOTH measured 9.1 ohms. Not 8.2 incidentally the replacement resistor also measured 9.1 before installation.
I saw people remove the resistor a few different ways. I opted for the easier of 2 ways. I saw the two poles coming up to the resistor and decided to use those to solder the resistor wires to.
I gave the resistor a snip on both sides and removed the undersized resistor.
Then I was left with this.
The poles were well soldered into the board and they really seemed to be well attaached to the board. I left them there. If you wanted to mess with it more you could remove the screws on the board (there are about 6-7 screws and then that white connector right below the R2213 resistor is also connected underneath. So be careful of that. I am sure the purists will say to desolder the poles and put the wires right into the board but this worked quite nicely and seems very secure. The heat will be away from this board now so I am guessing that the heat in this area will be non-existent now.
At this point you will need some wire to solder to the leads of the new resistor. Tin the wires on both ends and attach one end to the resistor and then solder the wire to the posts of the old resistor. I used heat shrink tubing on the connectors. I really dont think it would ever touch the case but why even risk it.
So when you get it attached it will look something like this.
Check your solder joints. Mine were rock solid and didnt require any more work. It was attached to the post well and the post was still very solid to the board.
At this point you are going to have to drill a hole in you beloved case. Find a bolt that fits through the resistor, find a nut and I used a lock washer too. Why not? I also colored the head of the bolt with a red marker so it looks different from the other ones if someone else winds up with my rig 30 years from now.
A nice high speed metal drill bit will make quick work of the case. I used the bolt as a guide for the whole size I needed.
Watch out for those metal shavings. Those things can get magnetic and stick to things only to kill your rig when you spend all this time making this repair only to smoke it with those shavings. This is the position I drilled the hole with that way the shaving fell in front of the case or on the table behind.
Done with the hole ready to mount the resistor.
Once you have the hole drilled route the resistor to the hole and attach it with the bolt. tighten it so that you cant move the resistor you want a good mechanical connection to the case so that the resistor can transfer the heat to the metal case.
Now the resistor is mounted to the case. The heat the resistor generates will use that corner of the case to dissipate the extra heat and save your radio from the dreaded R2213 resistor.
For good measure I threw a zip tie on the wires and attached them to the existing wires in the area. Just to neaten up the job and protect the wires that much better.
Now you put the cases back on the radio and test. I SWEAR I hear people better now. I know that is psychosomatic and not real. It is nice piece of mind to have this resistor replaced. Both my radios are in GREAT shape from looking at the inside and outside of the cases. I really enjoy these radios too. I was a little nervous about cutting that resistor and doing the repair job but not anymore.
I also wanted to document this procedure as detailed as possible so ANYONE could follow these directions and do the mod. This is the spirit of Amateur Radio for me.
Special thanks to all the folks that guided me on this repair.
Tim WO9U (Thanks your pictures and the words that inspired me. "100 bucks or a 3 dollar part")
Chuck WD4HXG (Thanks for the info on the Yaesu repair info!)
also Splittingwedge off /r/amateurradio who really started me off and piqued my curiosity.
My radios are repaired now. I have been pounding on them for a few days and I am satisfied with the repair now.
