I have an ICOM IC M505 marine VHF which is the closest model to the one described below. It is less than 3 years old. The channels have been very quiet including channel 16. This prompted me to test the radio with the local coast guard. While the radio will transmit it is not receiving. The fault would appear to lie with the squelch control which is blocking receipt. any solutions Paul Dobbyn Dublin

Try Ebay as a source. I have had good luck finding such accessories for reasonable.

turn the squelch down? the RF gain down too
do you have an attenuator turned on ?

Contact the Icom service center. Their main web-page is www.icom.com. From there you can select your geographic area and service (commercial, marine, amateur, etc).

See the sensitivity if it is low then change the filter (wide) of your Radio.

You may download a copy of the manual from here.

First of all check if your antenna cable is in good shape.
Check if there are no shorts in the connectors between the center lead and the screen tress.
Also check if the center lead is soldered into his connector pin on each connector on the cable.
Set squelsh just out of the noise zone.

Blue: Speaker (+)
Gray: Speaker ( -)
Yellow: NMEA IN (+)
Green: NMEA IN (- )

Quick description as per ICOM Manuals:
Quote
The AF amplifier circuit amplifies the detected signals to drive a speaker. The AF circuit includes an AF mute circuit for the squelch. AF signals from IC1 (pin 9) are applied to the de-emphasis circuit (R61, C89). The de-emphasis circuit is an integrated circuit with frequency characteristic of –6 dB/octave. The integrated signals pass through the high-pass filter (Q5, R62–R67, C90, C91) to suppress unwanted lower noise signals. The filtered signals are applied to the AF mute circuit (IC7B), and then passes through the [VOLUME] control (VR board; R1) via the “VOL1” signal. The signals are applied to the AF power amplifier (IC6, pin 1). The output signal from IC6 (pin4) drives the internal (external) speaker.
Unquote
I thus assume the IC you are looking for is the IC described as IC 6.
Data sheet availible online: http://www.datasheetcatalog.org/datasheet/sanyo/ds_pdf_e/LA4425A.pdf
The IC is a Sanyo LA4425A. A 5W Power amplifier.

Sound like you have an antenna issue. Try a different antenna with coax. If the problem is still there, than you have a problem with the radio. Icom makes really good marine radios but you could have a defective one.

This applies to all battery powered radios. Take out the battery and measure the voltage to see if it is indeed charged. If it's not, then the fault is the charger or the battery or both. If the battery voltage shows that it is fully charged, then clean the terminals on the battery and on the radio with a pencil eraser to remove any corrosion. If still no joy, then look up in your user's manual on how to do a reset. If you don't have a manual, get on the ICOM website and download one.

Good luck.