Icom IC-706MKIIG Final HF Transistor Replacement

This video details the repair of my IC-706MKIIG. A final transistor failed in the unit, causing the radio to draw 10 Amps of current even when the power is off.
Older versions of the IC-706MKIIG (Like mine) used SRF-J7044 Mosfet transistors for the HF finals. Those transistors are now discontinued and are no longer available. I replaced them with RD70HHF1 transistors that Icom now uses. Unfortunately, they are not the same size, and circuit board modification was required.
Here is the video of the process.
Most of this information was found at EB5AGV's web site at:
jvgavila.com/ic...
Thank you a thousand times for the nice details that EB5AGV provided in doing this mod.
--John, K7JM

[@timwilliams2418]

I just ground off a little off each side of the Source and it fit nicely and has been working for the last7 years with no problem

[@SMShannon55]

It was great to meet you and your wife this past Saturday at the swap meet. Seeing how carefully you made this repair I’m delighted to be the new owner of this radio, John. I used to do electronic prototyping and we went through components sometimes. If you ever have another job like this, rather than trying to pry up all the leads on failed components, which could stress the pc traces, just cut the legs off and then desolder and remove the leads one at a time. That way they lift right off.

[@k7jm]

It was nice meeting you too. Thanks for the tip. I hope the radio does you good. BTW, I forgot you callsign. 73.

[@SMShannon55]

@@k7jm AI7KS. Do you ever check in to the Montana Sheepherders Net? 10:30 am Monday, Wednesday, Friday. 7.214 MHz

[@misterspock590]

I mentioned filing down the new transistor to fit the original opening a few years ago and never received an answer. But he did a hell of a good job!! Me, I would have ground the transistor down and will do this when the time comes. 73

[@TheTemporalAnomaly]

Much neater job would be to grind down the copper heat spreader on the transistor, I agree! That`s what my 706 will get if mine ever pop.

[@karlfrederick5731]

Excellent work. I recently sold my 706 MkIIG to a happy buyer -- however he became nervous as he found out a day after he bought it, that finals were out of stock. Naturally the rig works fine, but made an impression thinking its a problem to find parts if, and when.... Then came along the great work of EB5AGV and your step by step walk through. Nicely done. My buyer should feel better knowing its not the end of the road. -- and thanks for the tip on Ambient Symphony -- good tracks.

[@SMShannon55]

My granddaughter likes the background music, John. I shazamed it and found it was Battle at the Misty Valley by Zero-Project. She’s listening to more of their music now.

[@k7jm]

Good. I listed the music credit at the end of the video. It is free for non-commercial use. I'm glad she likes it. You can read the comments in how many people didn't like it. haha. I found it here: www.jamendo.com/album/195024/ambient-symphony?language=en

[@kg3m]

Wow guy, While watching your video I was glued to the screen wondering if that mod would take. I have a Mark 2 myself and so far there hasn't been a problem. I really love my 706 and would be very disappointed if I couldn't find the parts to repair it. When you took a dremel tool to the circuit board I said to my self "Good God" but you succeeded in repairing the board so great job....73, don...kg3m

[@jwhardig]

At field day I was given a 706 mark II for free. Now I know why. The guy that gave it to me knew the finals were out and even told me what happened to them so now I know the rest of the story. Thank u for this video. I may get this thing working yet. Apparently a CB guy got ahold of it and tried every band with only an 11 meter antenna. Don’t know what else he may have done but it’s going to make me a good project radio. 73 de Jeff N9NJN

[@CarlosAvellanet]

Nice vid. I still have my new transistors in a bag for over 5 years, This makes me want to dig the rig out and change them.

[@dash8brj]

Seems you had a bit of a struggle with the RF port - until you unscrewed it :) Like the music too - glad you referenced it so I could go get a copy. I have it playing while I am working on an icom as well with low power on vhf (ic746pro) :)

[@k7jm]

Hind Sight is 20/20. Good ideas on trying to trim down the transistor bases. As for other comments, I am an "amateur". I did something crazy like trying to repair my radio, and succeeded. -John. K7JM

[@MrNeduddgi]

My congratulations John, to the excellent work on that pretty radio. I hope you finished with the bias adjustment since then with the same professionalism and use the rig with satisfaction as before. 73, Bela HA4YF

[@scdevon]

Nice work, but why not just trim the heat sink on the RD70 transistors a little rather than hacking open the main board so much? I don't think any of the junction regions of the transistor would be affected by taking a good healthy trim off of those heat sinks. I know the transistors are engineered to have a certain mass and area of the heat sinks, but I think they would survive just fine.

[@jimasp7179]

John (K7JM) or others: I'm in process of replacing failed Motorola finals with a pair of Mitsubishi RD70HHF1 and noticed that on the new FET, the Source connections (screwed into the heat sink) do not have a direct connect to the PCB as the old SRF-J7044 parts did. Is this an issue? Was thinking perhaps adding a copper strap bridging the (4) PA PCB connections around the FET to the screw and soldering too. Any thoughts? Thanks, Jim k0dc

[@dougg9189]

Amazing positive job well done. A+ . I'd hire you if i was a icom business owner

[@arizonabobusa]

Like cypher526 mentioned , why couldnt the new style transistor bases be reshaped by gently grinding ? Pretty sure they are just aluminum and there isnt too much difference in them . Obviously the warranty would be voided if you modified them but still would be a lot easier than reshaping the pcb and risking breaking it .

[@gordonlawrence1448]

Most use tin on copper for thermal conduction unless things have changed since I worked in electronics (386 vs 289 for ally). Also copper is nearly twice as hard on the Rockwell(B) scale so would not make as good a contact to a heat sink. I would therefore try hand filing on a dead one first (small files).

[@Species-rj9si]

No static mat, no wrist strap AND wearing metal jewelry (ring on left and and wristwatch). Now that's working without a net!

[@SWRadioConcepts]

Species 5618 And apparently keyed it up with no antenna connected to the HF jack. yikes!

[@3butalcomp3]

+Species 5618 I have to agree with you, and yes, those transistors can be shaved. I'm not going to insult him because according to the video (with time lapses though) he showed a working radio in the end but made it hard on himself. I would have used a $10 Spring loaded Solder Sucker, they're great... instead of the desoldering bulb/iron, because they work so much better- then clean the board as always. I also would have wiped clean the old thermal schmegg, before reassembly. But that's just me... The static risk he took with that type of circuitry I'm surprised he didn't have further issues. NO net there!

[@k7jm]

Yup. Sorry about a reply 9 years late. I am an AMATEUR radio operator. I had a dead radio and I fixed it. I wasn't even wearing a seat belt or a helmet! Or a mask!

[@1OFGODSOWN]

So happy my 706 MKIIG is a late model so the change would be much easier if ever needed.I would never own another 706 or 706 MKII just for this reason.No way would I do that to the board.

[@cypher526]

I wonder if anyone's tried filing/shaping the new transistors to fit the existing pcb cutouts.

[@albertdicaprio7322]

Este señor puede ser un gran radioaficionado, como técnico deja mucho que desear, como corta la placa para poner transistores NO originales ?? como NO ajusta la corriente de repozo después de cambiar los mosfet ? como mide potencia, con un wattimetro de cualquier marca y antena ?? no con carga fantasma ,

[@czorgormez]

but you must be careful when you are doing this. there could be invisible inner layers on the pcb and you can easyly break them.

[@nasondasdoradioradioamador4558]

Greetings dear friend. Could you help me access the Icom IC-706 MKIIG MODE SETUP? I don't know the type and configuration of the plug connected to REMOTO to access its service menu.

[@NN3RP]

Excellent performance! You made this video to seem to be easy to replce the parts. Did you ever adjust the bias so that the rig output properly?

[@warplanner8852]

Rafael..that is an excellent question! Critical for finals r&r!

[@zaperfan]

Excellent work

[@SWRadioConcepts]

N5NR doesn't care about your radio, he just wants the contact then NEXT.

[@deanagoes2791]

Good job

[@Mr_Meowingtons]

good job dude!

[@jerrydavis266]

Hello, I have a Yaesu FT2800m with no TX power out How much does this cost to fix? Can I ship it to you for repair?

[@BAKKER2727]

super

[@golden-balls-radio]

you're supposed to remove the old paste....geeze

[@k7jm]

Six years late with a reply. Sorry. I am an AMATEUR Radio Operator, not a Professional. I had a dead radio and I fixed it. I wasn't even wearing a helmet and knee pads!

[@spikey911usa]

What was the cost of the finals?

[@tonyi5001]

They are now 251.00 a per item www.rfparts.com/rftransistors/transistor-rd/rd70hhf1.html

[@tonyi5001]

I did another search and found a matched pair for 36.00 each. www.ebay.com/itm/303125129974?epid=1854244752&hash=item4693aa6af6:g:FcEAAOSweLBaafkb

[@richardhardy8603]

ARE YOU AVAILABLE FOR ic QUESTIONS RICHARD HARDY KG7KHQ

[@petchharrison]

oh dear lets burn the red wire .. jeff .,.

[@w6by]

Your shakey video near the end of this piece is making me dizzy.