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eHam Forums => Elmers => Topic started by: W5WSS on December 13, 2010, 12:15:36 PM



Title: Any common problems with the Ic 718?
Post by: W5WSS on December 13, 2010, 12:15:36 PM
I have been using an Icom 718 for a few years and has been a good rig until recently. I am wondering if anyone else has experienced any problems with their transmitter. Mine has very recently started shutting down.and does so intermittently. The symptoms suggest RF common mode but until I can bypass everything in the system and look at it isolated with a dummy load I am guessing. Anyway I find it useful to ask if anyone has had their transmit shut down while watching the internal meter,mine will read some 75% deflection but in actuality is not transmitting. This question is mostly academic but could reveal some common problems we are experiencing. Thanks 73


Title: RE: Any common problems with the Ic 718?
Post by: 2E0OZI on December 13, 2010, 01:48:56 PM
Just bought mine yesterday still with 8 months warranty left on the clock, but any replies will be of interest to me!


Title: RE: Any common problems with the Ic 718?
Post by: KE4ILG on December 13, 2010, 02:08:49 PM
This may be an overly simplistic thing to check but I understand Icom's are finicky about the power supply.  If the voltage drops, which would happen when transmitting, it might cause what I understand you to be describing.  If possible trade out your power supply or hook it up to your vehicle and see if that solves you problem.  I had what seems to be similar problem with my Yaesu FT-950.  The fan to my switching power supply had stopped working and I had not noticed.  When I transmitted for a short time, shorter when on ssb instead of cw, the rig acted badly and shut down. The power supply was overheating and the output was not what it was supposed to be.  Replacing the power supply corrected the problem.  Out side of that I've heard nothing but good about the Ic-718.  73, Mike ke4ilg.


Title: RE: Any common problems with the Ic 718?
Post by: K9WJL on December 13, 2010, 04:19:06 PM
I wonder....
 I had a 706MK2G in the truck at one point, and the thing would shut down while tuning the screwdriver antenna on 40M.
Unplugging the external speaker while tuning eliminated the problem.
I don't know if this helps or not, but I wonder if the rigs share a similar design and I thought I'd throw it out there in case it was the issue.

73,
 Bill K9WJL


Title: RE: Any common problems with the Ic 718?
Post by: AD6KA on December 13, 2010, 04:40:21 PM
I wonder....
 I had a 706MK2G in the truck at one point, and the thing would shut down while tuning the screwdriver antenna on 40M.
Unplugging the external speaker while tuning eliminated the problem.
I don't know if this helps or not, but I wonder if the rigs share a similar design and I thought I'd throw it out there in case it was the issue.
That sounds like a common mode current getting into the
radio issue, especially tuning a short loaded antenna on a band
like 40m. But through the external speaker input? Never heard
of that one.


Title: RE: Any common problems with the Ic 718?
Post by: VA7CPC on December 13, 2010, 04:57:11 PM
My first thought:

. . . Check the power supply, DC wiring, _and fuses in the power cord_.

A loose or corroded fuse holder (or fuse) can masquerade as all kinds of trouble.   I just learned that the IC-7000 is notorious for "corroded fuse" troubles.

If it had a separable face-plate (a la IC-706), I'd suggest checking the wiring to that, as well.   But the IC-718 is a "one-box" rig.

                 Charles


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 13, 2010, 05:46:27 PM
A few minutes ago I connected the rig to a dummy load and it works normally. 100% every test. 100 watts output fine. I use this rig in my automobile on a hilltop stationary only. The only common denominator from that mobile antenna and to my other antenna system (rig is ungrounded in a second floor apartment) is that I do not have a grounding strap connected from the designated ground terminal on the rig to ground in either case. I have double checked both antenna systems for faults and find none. Perhaps a 6" long and 1" wide grounding strap connecting the rig's grounding terminal to the car frame could shed some more light on this new development it worked fine for a few years in the mobile. Not sure what changed yet. but am looking for the cure.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 13, 2010, 08:03:57 PM
Well...after some careful review of the service manual we see that there is an swr threshold setting that I changed from 1 to 2. the difference between a dummy load being purely resistive and an antenna that is above that threshold is the resulting difference. I think the swr cutback circuit was too sensitive at setting 1. You know it is interesting to note that nothing was mentioned about this in the manual that came with this brand new in box unit. There is much to be gained from the service manual too bad it was not included with the purchase of their new gear.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 14, 2010, 06:29:48 PM
Well here is an update. After reading through the suggested steps Icom wants us to connect the rig to a 100 ohm dummy load. eh em anyone have one of those? So in essence what we are doing is creating a window for the protective circuit to work within. I am able to set it to 50 ohms resistive but not the upper 100 ohm threshold. We are thinking the protective system which involves ALC ,output power, and current have grown apart for reasons not fully clear at this time but we need to complete a diagnostics for a more complete view of what is causing this erratic behavior and indeed rf common mode is always a possibility but may be only a minor player with this symptom.


Title: RE: Any common problems with the Ic 718?
Post by: AD6KA on December 14, 2010, 07:33:56 PM
Quote
A few minutes ago I connected the rig to a dummy load and it works normally..
In the car with the battery, or at home with a power supply?  If it messes up in the truck, check the battery voltage at key down when it faults Both with and without a dummy load. Does it NOT fault if you turn the power down?
What kind of antenna are you using in the car and on what bands?
Quote
the difference between a dummy load being purely resistive and an antenna that is above that threshold is the resulting difference.
I’m not even going to guess what you are trying to say here.
Quote
I think the swr cutback circuit was too sensitive at setting 1..
Maybe, but you said the rig was “shutting down”.This usually means turning itself OFF.
Is the rig in fact turning itself off or is it a power foldback problem?
High SWR foldback does not turn the rig off.
The former sounds like a voltage problem, as has been mentioned, and the latter
sounds like an undetected antenna problem or coax short.
Regardless, you should set the SWR circuit back to the factory default
AND do a microprocessor reset before you proceed any further.
Quote
We are thinking the protective system which involves ALC ,output power, and current have grown apart for reasons not fully clear at this time but we need to complete a diagnostics for a more complete view of what is causing this erratic behavior and indeed rf common mode is always a possibility but may be only a minor player with this symptom.
Who is “we”? You have a qualified Tech helping you?
Not sure how circuits “grow apart”.
It’s impossible to even tell what is going on given little information on antenna type, bands used, modes, power levels tried,
power supplies, type of connections, etc…not to mention use of the rambling verbiage.


Title: RE: Any common problems with the Ic 718?
Post by: WB6BYU on December 14, 2010, 07:53:15 PM
A simple way to make a 2 : 1 dummy load is to put two 50 ohm dummy loads in parallel using a T
connector.  If you need 100 ohms just add a quarter wavelength of 50 ohm coax between the T
and the rig.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 15, 2010, 12:56:22 PM
Ad6ka The rig is folding back in output down to less than 2 watts while simultaneously displaying a pegged high swr reading that is no fault of the various antenna systems that we have connected to it. The rig works perfectly normal 100% of the time when connected to a 50 ohm purely resistive and non inductive load. There is not a voltage drop problem as measured under maximum load and when measuring at the rig nor is there a lack of ample current available when pressed. We is plural for a friend of mine here in town. What we are going to try next is to adjust the swr set feature to rule out the possibility that something changed for reasons that are not clear yet. We are going to raise the set 2 feature by using a 100 ohm purely resistive and non inductive dummy load. We hope this will settle the issue. Do you know for a fact that the default procedure will include this? By the way your critique of how I structure a sentence was rude. If you want to Elmer than please be polite thank you.


Title: RE: Any common problems with the Ic 718?
Post by: WB6BYU on December 15, 2010, 01:35:54 PM
Did you use the same or different jumper cables for your various tests?  It sure sounds to me
like an intermittent connection in a coax cable, possibly the shield at some point.  It could
also be due to a cracked solder joint on the antenna jack, or an intermittent connection to
the center pin (such that some plugs make good contact and others don't, often due to
wear or corrosion on the plug or socket contact, or insufficient spring contact pressure,
often due to using a plug with too much solder on the end of the pin that spreads the
contacts apart.)

This is based on the behavior of the SWR meter in the rig:  if the SWR jumps up it shouldn't be
due to the shutdown circuitry.  (It might TRIGGER the shutdown circuitry, of course.)  If the
SWR is normal but a bit above the threshold, you should see it remain the same when the rig
shuts down.  (This presumes that the meter is programmed to respond in a "reasonable" manner,
of course, which isn't always the case with some microprocessor-controlled rigs.)

It is possible that some RF is getting into your reflected power sensor - again I'd look for a
broken bypass capacitor or poor shield connection if that is the case.  But I've been bitten
may times by poor connectors - perhaps the most common ones are BNC plugs where the
center pin has receeded into the housing, or worn down (especially from vibration when using
a rubber ducky on a bicycle.)  Some combinations of connectors make contact, others don't,
and it can be quite confusing.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 15, 2010, 05:27:50 PM
Wb6byu hello, I am using PL-259 silver with Phenolic Amphenol connectors. I soldered them. The center conductor is slightly visible I do that so I can see that it has not receded and is embedded in the solder at the connector end. The shielding is soldered at all four holes around the connector. anyway there are no faults with my antennas power supply etc. Update: I just witnessed the malfunction when connected to a 50 ohm dummy load so the problem has now been isolated down to the rig alone. The power dropped down from 100w to 2w pep yet the alc was intact and the swr was 1:0  If I wait a few minutes it recovers to 100 watts pep but drops back after transmitting for about 30 seconds.


Title: RE: Any common problems with the Ic 718?
Post by: N4PSE on December 16, 2010, 03:20:23 PM
Sounds similar to a problem I recently had with my ProIII. See my posting under this forum and under "mods and repairs" for 756ProIII output problems. Turned out to be a bad driver MOSFET. Not sure what the 718 uses, but that might give you another angle to look at.  Good luck, Jim


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 16, 2010, 03:51:45 PM
N4pse I think you are on the right track here. The problem may be a poor solder joint on the pa board but the underlying question that concerns me is whether or not Icom has suffered a bad batch of electronic parts. I wonder if our rigs were constructed around the same period?


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 17, 2010, 10:10:08 AM
While attached to the 50 ohm non inductive dummy load today I observed two different problems #1 this output power drop-off from 100 watts to 2 watts  occurs on 17M 15M 12M 10M only. #2 The rig just transmits full power regardless of mode this includes ssb where I am NOT modulating. During the #2 problem  I noticed that when I change mode via the mode select push button It has no effect on the transmitted signal but rather it just transmits full out of control output while simultaneously displaying normal swr reflection normal alc just full power output when pressing the ptt switch regardless of mode. None of the two problems has ever been manifest on 20M and down. So this odd problem is with the 17m 15m 12m 10m bands.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 17, 2010, 07:30:34 PM
Any more problems? please feel free to add yours.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 18, 2010, 06:54:54 AM
I discussed the symptoms in great length with Kk5j here in town and he directed me to the wiring harness that is located near the j17 trimmer. I carefully unplugged it and properly cleaned it plugged it back in. The transmitter is now working properly on 17m 15m 12m 10m. The harness does have some tension on it as a function of routing, whether this is a problem time will tell. I must say This has been a real thorn for awhile as I went looking for common mode issues. On a positive note I have a very healthy antenna system and power supply system in the mobile. Please feel free to post any other issues with the 718 thanks.


Title: RE: Any common problems with the Ic 718?
Post by: WA8MEA on December 18, 2010, 07:58:00 AM
I've had numerous 718's over the years.

One common denominator: They all went nuts (as you describe) with excess RF in the shack.

Also, I've had other rigs perform as you describe that don't have large enough wiring to carry the current from the PS to the rig....even in short lengths.

I've also had Yeasu's go nuts with RF when connected to ANY power supply, but work perfectly fine with a marine battery.

So...have fun!  Experimenting can be educational!

73, Bill


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 21, 2010, 12:21:22 PM
Thanks Bill. Yes while it is certainly possible that a low voltage condition would or could depending on a few variables. I have several contingencies with respect to power supply and voltage drop has been investigated  and dismissed as well as the various antenna systems found to be without fault. the latest theory is that the problem is in fact within the rig but I am only speculating at this time and will reveal more upon discovery meanwhile fellas keep posting your issues ans comments with otherwise great little rig. Thanks and 73


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 21, 2010, 12:43:24 PM
N4pse yes I am looking at the various pitfalls associated with transmitter fold back  protection circuitry. Interestingly within the many specs contained in the Mitsubishi data sheet of the 2SC2904 a maximum temperature of 150 degrees in every case causes total shut down of the mosfets output power. As you know there is a thermal resistor that works with two separate transistors to control the hi and low fan speed for temp control of the finals. Heating and cooling with time about 30 seconds in my case for total restoration back to 100 watts pep. Due to the possibility of damage caused by a problem with cooling I must stop transmitting until that possibility is ruled out.


Title: RE: Any common problems with the Ic 718?
Post by: AD6KA on December 21, 2010, 02:44:09 PM
Quote
#2 The rig just transmits full power regardless of mode this includes ssb where I am NOT modulating.

How can the rig transmit ANY power in SSB when you are NOT "modulating"?

If the rig truly is in SSB mode and you are keying the mic
*without* speaking into it, or injecting an audio signal into
the mic circuit (PSK, AFSK, etc), then there should be no power output at all.

Quote
Mitsubishi data sheet of the 2SC2904 a maximum temperature of 150 degrees in every case causes total shut down of the mosfets output power.
Are you looking at the "Collector Dissipation vs. Ambient Temperature" chart?
Collector dissipation is not the same as "output power".
And that's 150 degrees Celsius....302 degrees Fahrenheit.



Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 22, 2010, 04:39:04 PM
Ad6ka are you asking me? I said 150 degrees. I also said it outputs power even when I am not modulating the transmitter when in the ssb mode. I am discussing the symptoms. I asked you a question that you did not answer.


Title: RE: Any common problems with the Ic 718?
Post by: KT4WO on December 24, 2010, 06:59:51 AM
I must agree with AD6KA, I have the 718,,,had it for 5 years without ANY problems. This is a VERY
solid radio that is 100% duty cycle. You have other problems. Its a jumper..or something would be my bet.

You are going in directions that you don't need to and don't sound qualified to.

Go buy a new jumper, and stay away from the finals.

Trip - KT4WO



Title: RE: Any common problems with the Ic 718?
Post by: KT4WO on December 24, 2010, 07:10:25 AM
---AND--- reset the SWR protection!!.. or you will be replacing the finals.

You have RF problem or maybe a low power supply issue... Don't know for sure, but
it does not sound like a radio issue per se.

Try a new jumper, power supply and dummy load. THEN if you still have the problem...maybe its the
radio:) 

Trip - KT4WO


Title: RE: Any common problems with the Ic 718?
Post by: KB4QAA on December 24, 2010, 11:51:31 AM
IMHO, there is no reason for the average ham to be messing with the SWR protection settings on a 718!!  EVER.

If one doesn't have a well equipped lab, and one doesn't have either formal training or years of repair experience you are going to screw up radios, not fix them.

I feel like a lot of the 'supposing' here has been chasing self painted zebras rather than something being originally wrong with the radio.

I recommend doing a hard reset on the radio and taking it to an experience ham technician who has the service manual, rather than doing any more self repairs.

Good luck!



Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 25, 2010, 11:37:43 AM
More than a month ago, prior to starting this thread I did the hard reset. The swr set procedure is in the service manual and is easy to do. Ad6ka comments are after the fact and only relevant with respect to a Properly working rig and is not the final word on this subject because contrary to his critiques (as opposed to helpful hints) one of the two symptoms with my 718 is that the rig is in fact outputting out of control even when in the ssb mode and not modulated by the user. Leaving me with only one problem remaining and that is this, after about one minute of transmitting at full power on ssb the rig drops to 10 watts pep and remains so unless I stop transmitting and I wait 1 minute which at that point will repeat exactly again with 100 watts down to 10 watts. I fixed the first problem leaving only the heat related thermistor issue. The spirit of this thread was meant by me to be helpful and informative associated with the common problems we experience with the Ic 718. To those whom wish to post their issues with this otherwise nice rig please feel free to do so It is not my intention to be critical of our fellow ham operators on whether or not they are qualified to read and use their service manuals. 73


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 25, 2010, 11:53:01 AM
Kt4wo hello did you know that Icom redesigned the pa board and use different finals than they did 5 years ago? I have already isolated and fixed one of the two transmitter problems. 73


Title: RE: Any common problems with the Ic 718?
Post by: KT4WO on December 26, 2010, 05:14:04 AM
"Kt4wo hello did you know that Icom redesigned the pa board and use different finals than they did 5 years ago? I have already isolated and fixed one of the two transmitter problems. 73 "

No---I did not.
But....When someone starts disabling the SWR protection, It make me question their
qualifications.

Good Luck and 73

KT4WO



Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 27, 2010, 01:47:31 PM
kt4wo I am not disabling the swr protection as there exists no adjustments for that complex circuitry, nor ever intended to. The service manual describes setting (not disabling) the swr threshold in detail and is a user preference, it is not hazardous to the rig. You may read all about the proper settings recommended by Icom. We are qualified to learn as ham operators including me. Sending the rig in for someone else to fix as you mention is advise that I've taken a few times over the past 40 years. I must state here my 718 has been problematic and is by no means comparable to a Kenwood Hybrid I've owned since 1978. 


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 28, 2010, 12:25:39 PM
Update. The two transmitter symptoms I have experienced with my Icom have been found to be a faulty driver stage. So to those whom are interested note, that as the mosfet/s begins to fail it can do so in several ways. Mine exhibited either out of control oscillation (actual output) yet uncontrolled and irrespective of mode, even on ssb without modulating the transmitter! Or even when everything seemed to be working well on the air suddenly a dramatic drop in power 100 watts pep to below 5 watts. Sometimes one symptom or the other but never both at the same time. This was a real hair puller for me to diagnose because the transmitter behaved similar to one affected by a common mode problem albeit I was reasonably confident that the real fault would eventually be found in the rig and soon be obvious and voila as the mosfet failure progressed away from marginally intermittent to a more constant condition we then saw power drop when outputting into a purely resistive and non inductive dummy load. To those whom wish to post your issues with your Icom 718 please feel free to do so thanks and 73


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on December 28, 2010, 01:27:25 PM
N4pse Hello, here is a list of what transistors are used in my 718. The Pre-driver is a 2SC1971. The driver MOSFETS are a pair of 2SC 3133. The Power amp finals are a pair of 2SC 2904. Were your drivers the 2SC 3133? Thanks.


Title: RE: Any common problems with the Ic 718?
Post by: N9VO on December 28, 2010, 07:07:29 PM
Any chance that rig ever had the golden screwdriver inside????


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on January 02, 2011, 12:22:57 PM
No chance.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on January 14, 2011, 07:00:47 AM
The later Ic-718 use different mosfets. The pre driver is a Mitsubishi RD01MUS1, The pair of Drivers Mitsubishi RD15HVF1 and the Finals are a pair of Mitsubishi RD70HHF1.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on February 01, 2011, 06:55:06 AM
The rig has been working fine since replacing the drivers. Once I realized the drivers were in a process of failure, in retrospect as I reported the changes as they occurred it is now evident how to interpret such an issue that is becoming more common as the 718's are aging your milage may vary! so to those who have followed along It is my hope that some valuable information has been relayed. 73


Title: RE: Any common problems with the Ic 718?
Post by: M5AEO on February 01, 2011, 12:43:56 PM
I had a wierd problem with my 718:  If you touched the metal mic-hanger onto the screen of the mic plug it would start scanning!  If it can do that, nothing surprises me! ???


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on February 03, 2011, 08:04:08 AM
My rig behaved similarly, however I just tried touching the mic hanger to shield but it does not cause the scanning anymore. ? I wonder if anyone else has this weird issue? 73


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on February 06, 2011, 12:34:51 PM
Fellas, surely there are some amongst us whom have had other issues with this rig?


Title: RE: Any common problems with the Ic 718?
Post by: KB4MB on February 08, 2011, 05:05:45 AM
Been using the rig for a year an a half daily with no issues.  Solid little guy.


Title: RE: Any common problems with the Ic 718?
Post by: W5WSS on February 09, 2011, 10:17:12 AM
Hello kb4mb, Mine is about a year and a half old. You have been using yours for about the same amount of time. I am curious when yours was manufactured? Icom has changed brands of the pre driver the drivers and the finals to Mitsubishi. I hope ours are the same, which brand are yours? I hope mine failing was just an anomaly and not some common fault with the lot. 73 thanks for your input.


Title: RE: Any common problems with the Ic 718?
Post by: KE5LZL on June 19, 2013, 07:06:20 PM
After working Jt65... I noticed that the power dropped down on 20m... but on 10-18m no problems at all... I notice that the Icom 718 was hot on the back .. .
I bareley get out 2-3w   ..I don't know if it's the IT-100 tuner or the amp stage in the Radio..
Anyone have suggestions..?


Title: RE: Any common problems with the Ic 718?
Post by: K4LJP on July 04, 2013, 04:41:47 PM
I have an Icom IC718 that displays an unusual problem. It seems to function perfectly in every way except the PO meter function. When transmitting, it reads PO at 50%, period, all modes, all bands with or without modulation.
When using an external watt meter everything seems to read normal. Any one with this experience? I know it seems minor, but it ain't right!!
de Lee
K4LJP


Title: RE: Any common problems with the Ic 718?
Post by: NO2A on July 04, 2013, 06:59:23 PM
This reminds me of a similar problem with the IC-706. That rig would go into a self oscillation on 15/17m. Don`t know what version but it was a popular problem with those.


Title: RE: Any common problems with the Ic 718?
Post by: AE7VA on May 22, 2015, 05:05:51 PM
I'm having the same problems with my 718; purchased March 2011.  10-17 meters I get out of control oscillation; sometimes affects 20m.  30m and lower is unaffected.  I'm assuming its also a faulty driver stage based on reading these threads.

Has anyone sent theirs to an Icom service center for repairs; and if so, were they able to fix it?

If they redesigned the PA board, do you think it is cheaper to purchase a new radio or replace the board?