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Old 25 October 2010, 14:55   #1
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Electrical gremlins with the radio

Having had a good few issues with our Raymarine RAY 240E, we finally thought that having fitted our repaired units today that we would at last have a functioning fixed radio.

For a sort of dummy-run, I put the box into the console and plugged everything in without screwing it in: although the repaired handset didn't work quite as it should, the brand new one from the second set we have acquired appeared to function perfectly, even retaining our MMSI when switched on and then off again!

Having screwed the box back into the fibreglass, I plugged everything back in: appears to work fine, turns on, receives well, still contains MMSI......however....whenever you transmit or just blip the transmit button, the trim tabs turn on! The LEDs on the display do their little warm up thing, and then the closing thing - when the power is cut they normally retract to the raised state -, and even though the tabs are already fully raised the motors whirr for a second or so...very weird. Doesn't appear to do it when their down or even just switched on already but its strange when they do.

Our only two thoughts so far are that something is making an electromagnetic field collapse within the radio when the button is pressed and somehow this causes an issue with the tabs...or... alternatively, when the radio transmits it causes such a drain of current on the battery that the tabs are tricked into thinking that the power has been cut, although it wasn't even on in the first place, and the switch remained off continuously. Bearing in mind that we haven't tested it with a running engine yet, it doesn't seem quite right!

Although I'm doing a GCSE in electronics at the moment, my skills do not go much further than tracing the wires to their origins as I have done, the only interesting end enters a wrap of insulating tape and then emerges as a big thick cable plugged directly into the tabs box in the console. The only places anything related to the radio or tabs meet is at the isolation switch, and the handset cable is cable tied to one of the tab wires at a certain point, although both are heavily insulated.

Any thoughts would be much appreciated, in the short term, leaving the tabs "on" even when not in use would seem the logical option, although most of the time they are left down to a certain extent so not a problem.

Puzzzling!
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Old 25 October 2010, 15:26   #2
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I've no idea what your problem may be, but there's a couple of things you could consider, in an attempt to narrow down the fault.

Does it make any difference whether you are on high or low power for transmit? Does the radio actually transmit ok?

Are you able to temporarily power the radio up with a separate battery (to isolate it from the boat's wiring) to see if it still does it. If it does, then it suggests the problem is EMF interference based.

I'm assuming you haven't bent any pins on connectors or mis-wired the replacement.
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Old 26 October 2010, 03:53   #3
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If I was a betting man I would say you have some serious wiring issues on that boat!
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Old 26 October 2010, 04:19   #4
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Quote:
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If I was a betting man I would say you have some serious wiring issues on that boat!
Having looked at the original problem and been unable to get the fault to reproduce with anything resembling consistency I am inclined to agree!

Keith's suggestion of a separate power supply for testing the vhf is an excellent one.
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Old 26 October 2010, 04:41   #5
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Hi Martin,

We've made a bit of progress since you saw the boat. Raymarine found problems with both the handset and the main radio box which have been repaired. The radio now seems to work fine save for this strange interference. It's not as if the wiring is difficult to follow so I can't think what's happening.

David
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Old 26 October 2010, 05:16   #6
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I think I'd make sure the negative (ground) cables are well secured and making good contact. A quick test with a mutimeter would be ideal. Marine wiring problems are invariably 'ground' related.
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Old 26 October 2010, 05:25   #7
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Quote:
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Marine wiring problems are invariably 'ground' related.
A bold statement, but I am not going to disagree.
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Old 26 October 2010, 07:34   #8
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Are they the Lenco trim tabs, with the seperate signal wire for power?
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Old 26 October 2010, 08:01   #9
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Hi
To give you an idea nowadays at just how sensitive modern electronics can be to RF interference, a few years back we suffered a problem on a 38000hp fast cat ferry (the ones which go back and forward to the Channel islands). We suffered repeated shut downs of one of the main engines during passages across the channel. The shut down would happen at random times but always concern the aft wo engines.

It took months to find the problem which turned out to be.................................passangers standing out on the lower aft deck using their mobile phones which in turn interfered with the electronic 'fly-by-wire' engine governors.

i'm not saying that this is your problem but as someone already suggested try transmitting on 1w then unplug the antenna completely and re-try.

Failing this, the only other output found on a 'leisure' VHF is an external speaker, do you have one in use? if so check the integrity of the cables.

Otherwise i would (as again,already suggested) temporarily run a dedicated fused supply and negative direct to battery to avoid any internal earth issues in the VHF itself.

Hope this helps.....oh and good luck

Simon
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Old 26 October 2010, 11:40   #10
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i'm not saying that this is your problem but as someone already suggested try transmitting on 1w then unplug the antenna completely and re-try.
I'd be extremely wary abouyt trying to transmit without an aerial attached. You could do a lot more damage than good. It certainly advises strongly against doing such a thing on my Icom. It may solve your interference problem though, cos it'll burn out the radio
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