eHam.net - Amateur Radio (Ham Radio) Community

Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net



[Articles Home]  [Add Article]  

Icom IC-706MKIIG PLL Problem

Stan Joosen (PA8C) on February 6, 2014
View comments about this article!

I had some problems with my rig. -- After heating up (approximately 20 minutes) the transceiver produces a crackling noise and a lot of his heard from the internal speaker when on 2 meters FM/AM/SSB/CW.

It took me about 3 nights to identify the problem and first of all I suspected a bad soldering joint or something like that.

Checking the PLL circuit diagram I noticed that the modulation circuit uses also part of the receiving circuit so I concentrated on that.

I checked the voltages from the 3 regulators on the PLL board bud couldn't find anything wrong there. So I figured out that the VCO mixes on approx. 216 MHz and tuned an Icom R10 receiver on the VCO frequency to establish if I could here it there too. That was the case so the culprit has to be in the VCO.

I opened the tin can where the VCO is located and tapped with a trim key on several components. When tapping on the trimmer capacitors for VCO1 and VCO2 I could reproduce the problem. So the two 6-10pF SMD trimmers are at fault.

These trimmers are Murata SMD types that are very small 3x3mm and one would never suspect that these would make a short.

Anyway I am going to reorder some new SMD trimmers and replace them.

73, Stan/PA8C

Member Comments:
This article has expired. No more comments may be added.
 
Icom IC-706MKIIG PLL Problem  
by SWL2002 on February 6, 2014 Mail this to a friend!
While interesting for IC-706 users, why is this an article?
 
RE: Icom IC-706MKIIG PLL Problem  
by PA8C on February 6, 2014 Mail this to a friend!
For the sole reason that this is a very rare fault and other people might need this information. After all the IC706 series is out of production since 2010 and in due time more and more problems will arise. One would not expect a variable capacitor to be at fault in a VCO.

73, Stan/PA8C
 
RE: Icom IC-706MKIIG PLL Problem  
by KG4RUL on February 6, 2014 Mail this to a friend!
"One would not expect a variable capacitor to be at fault in a VCO. "

ALL components have a failure rate. In point of fact, the more components, the likelier that a system failure may occur.

And I agree. Why is this an article???
 
Icom IC-706MKIIG PLL Problem  
by NY4FD on February 6, 2014 Mail this to a friend!
Stan,
Thanks for writing up your experiences with the 706. Harm radio is all about sharing. Very informative.
73 George
 
Icom IC-706MKIIG PLL Problem  
by VE3TMT on February 6, 2014 Mail this to a friend!
If it were me, I would have waited until the new parts had arrived and were installed, to guarantee your synopsis was correct. And then post the results of your findings.

The heading is misleading.
 
RE: Icom IC-706MKIIG PLL Problem  
by N1DVJ on February 6, 2014 Mail this to a friend!
I wouldn't say it was misleading, but I too would have waited until it was fixed before posting.

I've seen a lot of problem with SMD varicaps. Where I work there were two used in an antenna design, and they were a nightmare. I used the Murata parts on my redesign and the problems were cut by maybe 2 orders of magnitude.

Should I assume a 'resolder' has been tried on the parts? Some style of cap tends to 'swell' and with time go intermittent. Sometimes a resolder clears up the problem, at least for a while. While not a good fix, it would at least verified that the parts were surely the problem. While tapping with a wooden stick can help find the problem, it's still affects some parts around what you tap.
 
RE: Icom IC-706MKIIG PLL Problem  
by K2FOX on February 6, 2014 Mail this to a friend!
Thanks for the info, article or not (like it really matters). I own two of these radios and will archive this in case I run across a similar problem.

Thanks,

Jay
 
Icom IC-706MKIIG PLL Problem  
by K4EJQ on February 6, 2014 Mail this to a friend!
Hi Stan; Thanks for sharing this info. However, look out for " MISTAKEN CERTAINTEES ". The only way you'll know is if you replace the suspected components and operation returns to normal. To have two exact components fail in the same circuit of the same radio is only likely if the builder got a bad run of parts. It can happen. Let us know what you find after replacing the parts. I have four of these radios, HI!!
Good Luck with the project. 73, Bunky, K4EJQ
 
RE: Icom IC-706MKIIG PLL Problem  
by G0BYH on February 7, 2014 Mail this to a friend!
I think this problem has been reported on other sites and may not be actual components. This PCB has suffered with problems with the solder connections through the board from one side of the print to the other and has occurred at the point at which these trim capacitors are sited. I had this occur on my own radio and cured by re-soldering the connections. Hope this may be of help.
Geoff - G0BYH
 
RE: Icom IC-706MKIIG PLL Problem  
by SWL2002 on February 7, 2014 Mail this to a friend!
This would have been more appropriate in the Mods and Repairs forum instead of an article. Making it an article could lead some astray since we don't even know if the authors assumption about what was wrong was correct. He did not even fix it yet.
 
Icom IC-706MKIIG PLL Problem  
by W4XKE on February 7, 2014 Mail this to a friend!
I'm impressed that Stan took the time and trouble to post this "article" with good intent that it could be helpful to others. (Thanks, Stan!)

However, I do see the point - that it is only a complete waste to provide such information to those who have no incentive to troubleshoot or repair a circuit.

While I don't have my Icom 706 MKII-G any longer, I still find it interesting to learn what someone has discovered inside their radio. This is what separates hams from mere 'appliance operators' and we ought not try to discourage those who kindly offer to share their expertise.

 
RE: Icom IC-706MKIIG PLL Problem  
by WX7G on February 7, 2014 Mail this to a friend!
After replacing the trimmer caps the problem will still be there. Tapping the caps mimics the problem but is not the problem.

The tools to troubleshoot this problem are a heat gun and freeze mist. A common hair dryer can be used for heating and a can of compressed air - the kind used to blow off keyboards - held upside down will work for the cooling.

Heat the unit up until the problem appears then cool off sections until the problem goes away. This will lead you to the problem component.

 
RE: Icom IC-706MKIIG PLL Problem  
by N1DVJ on February 7, 2014 Mail this to a friend!
@W4XKE

I don't think it's a waste. It's always interesting to see other peoples investigative techniques. Even if he did stop short of verifying the problem.

As to the heating and cooling issue suggested, I agree. But only in the sense that he realized it was a thermal from the go.

I hadn't thought of turning the air can upside down. I wonder, will that work with all cans? While I understand the environmental impact issues with R-12, I sure do miss it on my bench.
 
RE: Icom IC-706MKIIG PLL Problem  
by N1DVJ on February 7, 2014 Mail this to a friend!
@G0BYH

Bad PCBs can be a real bear to find. When Radio Shack came out with their first digital scanner (called the Comp-100. Predecessor to the Pro-2001, but never in a catalog) it got rave reviews. It was a fantastic scanner. But it quickly turned into a nightmare for the company. This was the 16 channel all-band scanner that was programmed in binary by buttons under a little slide panel.

The scanner worked fantastic. When it worked. It was quickly relegated to the 'do not sell' category. But for those that already had been sold they needed repaired under warrantee. They were failing left and right. Someone said 100% failure rate within a few months. Some shops/stores gave up and just gave the customers a Pro-2001 as a replacement.

I never saw one that had a component failure. It was ALWAYS the plated through holes on the PCB. The 'fix' was to swap out the digital boards with National Parts that were reworked by the national repair depot. Story was these boards were working/new and then were 'baked' in an oven until they were warm and dry, then sprayed with sealant. The problem seemed to be humidity causing the boards to swell slightly and as a consequence break the vias. Once a board was 'broken' if it didn't have a simple fix, it wasn't worth treating. Even still, some failed after the treatment.

I picked up a Comp-100 for almost nothing and had a go at it. I stripped off wirewrap and soldered a piece in every single via I could get at. Once the board was working I baked it at about 120 degrees overnight then as it cooled, I sprayed it with a light film of Krylon clear. (I had access to a number of 'bad boards' but I actually got a few to work.)

I kept my Comp-100 for a few years until I sold it. (For more than I paid for it!) It was still working great and 100%, and the guy I sold it to still had it, as far as I knew, 5 years later. It was to this day the most sensitive and interference free (as much as a scanner can be free from interference) scanner I've ever owned.
 
RE: Icom IC-706MKIIG PLL Problem  
by VE3TMT on February 7, 2014 Mail this to a friend!
The TS940S comes to mind. Mine always seemed to develop a new problem just after I fixed another. Rebuilt the power supply, including the pass transistors, only to have the display blank out on me at random times. Traced it to the big IC (designator escapes me) on Control Board A. Kenwood's remedy is to remove the socket and solder the IC directly to the board. I was afraid of ruining traces, so I reapplied solder to every pin generously to let it flow through the vias. I then tinned each pin of the IC to add a little more thickness to the pins. It had to be forced back into the socket, but never gave me a bit of trouble after that. Resoldered just about every connector and plug in the radio. If there was ever a radio to develop solder issues, the 940 was it.
 
RE: Icom IC-706MKIIG PLL Problem  
by G3RZP on February 8, 2014 Mail this to a friend!
There have been reports of trimmer capacitors going bad after a few years for a number of rigs, so it's something to consider when VCO problems occur.
 
RE: Icom IC-706MKIIG PLL Problem  
by AC5UP on February 8, 2014 Mail this to a friend!
I've had trimmer caps oxidize the wiper arm contact point of the center shaft and jump value intermittently. The Q & D fix is to mark the position with a Sharpie pen then rotate 30 to 40 revolutions in each direction. Return the cap to original position and test as needed.

This isn't a permanent fix... Neither is replacing the cap, as the 'bad' cap used to be new, and can affect the alignment. Same as a cap replacement would.

Could be worth a shot.
 
RE: Icom IC-706MKIIG PLL Problem  
by N4JTE on February 8, 2014 Mail this to a friend!
What makes this "article" work is the informative responses and various suggestions for diagnosing circuit problems, I learned something !
Tnx
Bob
 
RE: Icom IC-706MKIIG PLL Problem  
by HAMMYGUY on February 9, 2014 Mail this to a friend!
"The TS940S comes to mind. Mine always seemed to develop a new problem just after I fixed another....If there was ever a radio to develop solder issues, the 940 was it."

EVERY TS-940S I've owned has had intermittent issues. The one I currently have is a fantastic rig until the intermittent shows up. This only happens once or twice a year when the rig has been sitting for a while. I've traced it to the IF board and resoldered every joint, connector, and etc. Before that it showed up daily! Glad I've only got about $100 into it.
 
RE: Icom IC-706MKIIG PLL Problem  
by KB5ZSM on February 9, 2014 Mail this to a friend!
Guess I've been lucky with my 940. I've had it for 5 years and other then a burned-out meter lamp, I've never had any other problems with the radio. It's by far my favorite radio!
I also agree with HAMS sharing info, whether it be here or in another forum. Hope those trimmers fix it but if they don't, don't give up!!! Good Luck!!!

Win KB5ZSM
 
RE: Icom IC-706MKIIG PLL Problem  
by VE3TMT on February 10, 2014 Mail this to a friend!
Half the fun is in fixing it yourself. I cursed the 940 more times than I can remember, but by the time I traded it off, it was working like new. Amazing receiver, great TX audio. Sometimes I wish I had kept it.

Good luck with the repair.
 
Icom IC-706MKIIG PLL Problem  
by K8YS on February 10, 2014 Mail this to a friend!
It is REFRESHING to find someone that actually works on their own radio! Good article.
 
Icom IC-706MKIIG PLL Problem  
by K2MAK on February 10, 2014 Mail this to a friend!
Hi Stan, Love your "article", it got me and I'm sure a lot of others to read your findings. Hope you fix your radio and post an update for the rest of us to see. Without folks like you who write articles about radio mods and fixes more radios would be sold as-is on the used market. I've fixed quite a few radios searching for articles like yours and been able to repair my radios.

keep up the good work and keep us posted.

Ken
 
RE: Icom IC-706MKIIG PLL Problem  
by K2WH on February 12, 2014 Mail this to a friend!
Gee, guy goes through the trouble to identify a problem with his 706 and gets criticized for posting his findings.

Strange how far we as hams have come. I wonder how many of the critics of his findings or his posting at all, know what he is even talking about.

K2WH
 
RE: Icom IC-706MKIIG PLL Problem  
by K7ETF on February 14, 2014 Mail this to a friend!
I think it was entirely proper and acceptable to point out the fact that the "FIX" had not been verified. I wondered about that myself.
Criticizing that as criticism deserves to be criticized.
Me thinks we need to "lighten up" a bit.
 
RE: Icom IC-706MKIIG PLL Problem  
by VE3TMT on February 16, 2014 Mail this to a friend!
He didn't post his findings, he stated what he thought was causing the problem. But the repair had yet to be made, so there is no way to know he was correct in his diagnosis. I am all for posting such things but only after the repair has been made and the issue resolved. Personally I'd rather know for sure the work Is going to fix it before I undertake it.
 
RE: Icom IC-706MKIIG PLL Problem  
by W4TMC on March 10, 2014 Mail this to a friend!
Grumpy old men with nothing better to do than criticize someone who is trying to help others. A pox on all you grumpy old men.

As matter of fact, as the transceivers age this phenomenon is becoming more acute.

Remember everything we need to know we learned in kindergarten -- Grow UP!
 
Email Subscription
You are not subscribed to discussions on this article.

Subscribe!
My Subscriptions
Subscriptions Help

Other Recent Articles
Fontana Students Talk to Space Station Astronaut via Ham Radio:
ARNewsline Report 1933 -- August 29 2014:
DX News -- ARRL DX Bulletin #35:
Just Ahead In Radiosport:
Major ARRL 2nd Century Campaign Gift from JA1BK Will Support DX Log Archive