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Old 09-03-2016, 07:14   #1
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Icom AT-140 Tuner Problem

Hi all,

I've got an Icom M802 using an AT-140 tuner with an insulated backstay. Until recently, I've had no problems tuning and have had good signal reports. Now I am unable to tune on certain bands at all. For example, 8 MHz seems OK, but I am unable to tune at all on 4 or 12 MHz.

I've checked connections and they are clean. I even did an experiment and ran a different piece of GTO-15 to the backstay with a longer length. Then tuning was possible on 4 MHz but I could not tune on 8 MHz any more.

I'm guessing that the tuner is toast, but if anybody has any ideas, I'm listening. I'm located in Provo, Turks & Caicos and am waiting for a window to sail to Puerto Rico. I'm not sure what the local situation for getting a replacement might be.

As always, the collective wisdom of the forum is greatly appreciated.
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Old 09-03-2016, 08:07   #2
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Re: Icom AT-140 Tuner Problem

Gary,

You may have surface corrosion on the control cable connections. These are really crappy connectors for the marine environment.

You need to be VERY CAREFUL in dealing with them. They don't just pull apart; there are little tabs to be depressed to release the connectors. Take your time, be SURE you are releasing the tabs, and pull them apart. Then, use DeOxit or similar electronic cleaner on both halves of each connection.

Good luck. The AT-140 is an excellent tuner, apart from the crappy connectors!

Bill
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Old 09-03-2016, 08:17   #3
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Re: Icom AT-140 Tuner Problem

If it turns out not to be the control cable connections the service manual .pdf is available for download from mods.dk website. Maybe there's a technician or an amateur radio ham nearby who can make use of it and help.

One of the relays you hear clicking as you change frequencies might be to blame if you're lucky. Find the right one from the manual and very carefully prise or cut open its little casing. Cleaning the contacts mechanically often saves them.

Sometimes a waterproof seal can fail.
Look carefully all around inside with strong magnification for signs of water ingress. Doesn't take much to cause failure, look for greenish or whiteish deposits.
A good technician can sometimes save a board by removing affected components and cleaning beneath. Corroded tracks can often be wired & soldered.
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Old 09-03-2016, 09:26   #4
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Re: Icom AT-140 Tuner Problem

Unfortunately, the control connections are not the problem. They're nice and clean. One thing I did notice is that when I successfully tune on 8 MHz, the tuner takes several seconds and makes the usual noises. When I try to tune on 4 or 12 MHz, it immediately gives up. In a split second the receiver shows THRU and the tuner makes no noises.

Oddly enough, it will tune on 14.300.
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Old 09-03-2016, 09:34   #5
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Re: Icom AT-140 Tuner Problem

unclemack,

Thanks, but I don't see any signs of water ingress. As far as cleaning a relay, I'm probably in over my head and am somewhat afraid of breaking it further. As of now I at least have the ability to tune 8.137 for Chris Parker Weather and 14.3 for an emergency.
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Old 10-03-2016, 08:27   #6
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Re: Icom AT-140 Tuner Problem

Hi

Have you been in any areas with lightning lately?

Even nearby lightning can fry the tuner, the symptoms are very similar to your problem, ie not able to tune on all frequencies. Funnily enough it may still tune on some frequencies after lighning damage, if it is not a direct strike.

Good luck

C.


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Old 10-03-2016, 09:35   #7
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Re: Icom AT-140 Tuner Problem

Have you checked the counterpoise, if the connection has gone due to corrosion or the strap has cracked it can effect tuning as much as the aerial connection. Standard test is to connect a length of 3" copper tape to the tuner ground and drop it over the side, if that resolves the problem re-do the counterpoise
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Old 10-03-2016, 11:29   #8
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Re: Icom AT-140 Tuner Problem

Thanks for the ideas. No lightning. Counterpoise is a KISS still sealed with no corrosion on the connector.

I've listened closely (stuffed into a small lazerette) while tuning is attempted. On 7-8 MHz, I can hear the usual noises coming from the unit. Not even a click is heard trying to tune on 4 or 12 (or higher than 12) MHz.

I've reluctantly concluded that the tuner is toast.

I have been able (for now) to tune Chris Parker weather on 8.137, winlink email on 7 MHz and Maritime Mobile Net on 14.3 so it looks like that's all I've have until I get to Puerto Rico (where shipping a new unit gets a whole lot easier).

Funny how reliant I have become on HF comms.
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Old 10-03-2016, 15:31   #9
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Re: Icom AT-140 Tuner Problem

Had the same problem --
Although I was able to get in there and clean the contacts, performance was marginal and I decided that the tuner is a life line that I wanted to be able to rely on.
Bought a new one as it seems nobody wants to repair them
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