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Author Topic: Any common problems with the Ic 718?  (Read 15226 times)
W5WSS
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Posts: 1657




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« Reply #30 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. 
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W5WSS
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Posts: 1657




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« Reply #31 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
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W5WSS
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« Reply #32 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.
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N9VO
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Posts: 157




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« Reply #33 on: December 28, 2010, 07:07:29 PM »

Any chance that rig ever had the golden screwdriver inside?Huh
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W5WSS
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Posts: 1657




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« Reply #34 on: January 02, 2011, 12:22:57 PM »

No chance.
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W5WSS
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Posts: 1657




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« Reply #35 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.
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W5WSS
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Posts: 1657




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« Reply #36 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
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M5AEO
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Posts: 259




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« Reply #37 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! Huh
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W5WSS
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Posts: 1657




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« Reply #38 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
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W5WSS
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Posts: 1657




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« Reply #39 on: February 06, 2011, 12:34:51 PM »

Fellas, surely there are some amongst us whom have had other issues with this rig?
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KB4MB
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Posts: 295




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« Reply #40 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.
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W5WSS
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Posts: 1657




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« Reply #41 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.
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KE5LZL
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« Reply #42 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..?
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K4LJP
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Posts: 38




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« Reply #43 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
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NO2A
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Posts: 761




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« Reply #44 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.
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