Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 18-06-2012, 15:35   #1
Registered User

Join Date: Aug 2009
Location: Toronto, Ontario
Boat: Mirage 29 - MOXIE
Posts: 5
Looking for advice - Icom IC-M45 VHF issue

I have an Icom IC-M45 VHF radio that has the following problem. Whenever I hit the mike's transmit button, the unit's display dims by about 50% and the "BATTERY" indicator blinks on the display. I don't have this problem when using using low power, only high power and it's not a battery issue since this happens even when the boat is hooked up to shore power or running with fully charged batteries.

I have had difficulty getting heard on high power but reception is fine so it doesn't look like an antenna problem.

I can easily replace the radio but I want to make sure it's shot before I spend the money.

Anyone have a possible explanation for this problem? It's not even listed in the user manual...

Cheers,

Moxie
__________________

__________________
moxieskipper is offline   Reply With Quote
Old 18-06-2012, 15:43   #2
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,619
Re: Looking for advice - Icom IC-M45 VHF issue

I think you have a bad connection somewhere.
When transmitting on high power the VHF draws a lot of current. When you have a high resistance connection the voltage drop is dependent on the current. Transmitting on high is causing the voltage to drop to a low level because of the bad connection.
Try a multimeter on the leads close to the battery. When transmitting on high you will see the voltage drop to say 11v or lower.
__________________

__________________
noelex 77 is offline   Reply With Quote
Old 18-06-2012, 15:52   #3
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 11,454
Re: Looking for advice - Icom IC-M45 VHF issue

Quote:
Originally Posted by noelex 77 View Post
I think you have a bad connection somewhere.
When transmitting on high power the VHF draws a lot of current. When you have a high resistance connection the voltage drop is dependent on the current. Transmitting on high is causing the voltage to drop to a low level because of the bad connection.
Try a multimeter on the leads close to the battery. When transmitting on high you will see the voltage drop to say 11v or lower.
G'Day Nolex,

I agree with your analysis, but shouldn't he check the voltage at the transmitter, not near the battery, if he wants to check line voltage drop?

Cheers,

Jim
__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is online now   Reply With Quote
Old 18-06-2012, 15:56   #4
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,619
Re: Looking for advice - Icom IC-M45 VHF issue

Quote:
Originally Posted by Jim Cate View Post
G'Day Nolex,

I agree with your analysis, but shouldn't he check the voltage at the transmitter, not near the battery, if he wants to check line voltage drop?

Cheers,

Jim
Oops sorry Jim you are correct I meant to say close to the VHF.
__________________
noelex 77 is offline   Reply With Quote
Old 18-06-2012, 15:59   #5
Registered User

Join Date: Aug 2009
Location: Toronto, Ontario
Boat: Mirage 29 - MOXIE
Posts: 5
Re: Looking for advice - Icom IC-M45 VHF issue

Roger that... I will take a look next time I am on board. I have a voltmeter in the breaker panel which is right next to the VHF unit so it should be easy to check. The connection should not be too hard to check as it goes right into the panel.

Thanks for the tip!

Moxie
__________________
moxieskipper is offline   Reply With Quote
Old 18-06-2012, 16:12   #6
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,619
Re: Looking for advice - Icom IC-M45 VHF issue

Quote:
Originally Posted by moxieskipper View Post
Roger that... I will take a look next time I am on board. I have a voltmeter in the breaker panel which is right next to the VHF unit so it should be easy to check. The connection should not be too hard to check as it goes right into the panel.

Thanks for the tip!

Moxie
The voltmeter will not show the problem if the bad connection is closer to the radio. The fuse holder fitted to most of the icom radios for example, some corrosion here will drop the voltage during high transmit, but the panel meter will still read 12.5 v.
One trick is to use 2 fine pins to pierce the insulation near the radio and measure the voltage during transmit. Ideally when you have found the problem you cut the wire and remake the connection although in practice the small holes made by the pins will reseal reasonably well.
__________________
noelex 77 is offline   Reply With Quote
Old 18-06-2012, 16:16   #7
Senior Cruiser
 
Jim Cate's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: cruising SW Pacific
Boat: Jon Sayer 1-off 46 ft fract rig sloop strip plank in W Red Cedar
Posts: 11,454
Re: Looking for advice - Icom IC-M45 VHF issue

Quote:
Originally Posted by noelex 77 View Post
The voltmeter will not show the problem if the bad connection is closer to the radio. The fuse holder fitted to most of the icom radios for example, some corrosion here will drop the voltage during high transmit, but the panel meter will still read 12.5 v.
One trick is to use 2 fine pins to pierce the insulation near the radio and measure the voltage during transmit. Ideally when you have found the problem you cut the wire and remake the connection although in practice the small holes made by the pins will reseal reasonably well.
If worried about the holes in the insulation, put a drop of "Liquid 'Lectric Tape" on them... seals them up effectively.

Cheers,

Jim
__________________

__________________
Jim and Ann s/v Insatiable II , lying Port Cygnet, Tasmania once again
Jim Cate is online now   Reply With Quote
Reply

Tags
icom, vhf

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 18:49.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.