Batboard

I have a 4 channel VHF GM350 with a problem. I think it might be a dry joint??

At power up from cold, the top red LED flashes. There is no receive audio BUT the radio still transmits BUT there is NO transmit audio, just a carrier.

After about 30 minutes, the GM350 started to work OK after I tried a few test transmissions and power cycles. The transmit audio came back first and then the receiver started to work...all the buttons lite up and started to bleep when pressed etc. I left the radio on all day and it contunued to work fine.

The next day, I initially had the same results..flashing red top LED etc. But after an hour warm up I had mixed results..the transmit audio eventually returned but the receiver started outputting white noise and the radio would switch off on its own. Eventually the radio booted up correctly.

Any ideas? As the radio seems to eventually work after its warmed up I guess it could be a dry joint - any idea where the dry joint might be..maybe a voltage regulator?? Maybe a head issue? Corrupted codeplug??

I actually think you have about 3 issues .......

Flashing red LED and some odd power up stuff - bad battery. Look at the batteries bar code sticker. There are 3 numbers to the upper left of it. First digit is the year it was made and the other two are the week of that year. I would suspect anything below say 2006 on a good day is bad.

Intermit TX audio and intermit RX audio - bad speaker mic jack. If you ( or a previous owner ) used a speaker mic I can guarantee you that is the source of those issues.

Intermitant RX ........The most common is a 44.645 crystal. If it fades more than about 1Khz - replace. They sometimes fade/drift off freq. or just fail all together. Another far less RX issue that I have encountered is the ASFIC chip that is essencially the RX chip. If the squelch noise is very weak and "fuzzy" then it probably is the 455Khz. ceramic filters.

I have fixed a million of these GP350's, P110's and GP300's !!!!

Hi
Try to resolder AFIC IC.

guy being a guy wrote:
I have fixed a million of these GP350's, P110's and GP300's !!!!

Actually, the GM350 he's referring to is an overseas mobile model.

http://www.batlabs.com/gm350.html

As wavetar says, its a mobile radio not a portable..it looks a bit like a GTX or LCS2000 mobile.

To summarize the issues :

- From cold , radio will always TX but with no mic audio..just a carrier. Top red LED will aways be flashing..but NO RX audio.
- As radio warms up, TX mic audio will return and red flashing LED will stop...but still no bleep at power up or when you press keys..and still no RX audio
- As radio warms up more and a few power cycles, RX audio will start to come back but it is intermittant..sometimes white noise..sometimes radio will just power down on its own..sometmes a whining noise from speaker.
- As radio warms up even more, full RX will return..or it did initially...it now seems harded to get the radio to start RXing correctly

It could be any number of degraded components (ie: electrolytic capacitors) or as you suggest, dry solder joints. I don't know the internal workings of the GM350, but it sounds very similar to the GM300 issues with dirty/oxidized interconnect pins. I suggest stripping it down and cleaning any & all pins/flexes & ground connections as a start. A can of cold spray to try & isolate sections of the board(s) once it's warmed up & working would be a good idea too.