Shuts for no reason

Check for any rust or corrotion on radio battery contact. dirty bat. contact could produce this kind of syntoms. What happend if the radio turn off by itself and you try to turn on again? does it turn on normaly?

Check the battery first..... alot of times a person will put a battery in a chager and let it sit. They will think the battery is fully charged but it may not be... In those battery packs there are a bunch of smaller batteries all tied together. Alot of times these commercial raios will run off of around 7 volts ( check the battery). The battery will only charge up to 7 volts if all the cells inside the battery are good. What I'm saying is for you to charge the battery up fully..... check the voltage listed on the battery then use a volt meter to check the voltage after the battery is fully charged. When a battery has just finished being charged usually it will be overcharged.... a 7.5 volt battery will be up around 8.5 volts for example. So check the battery right after its charged... expect it to be overcharged. If it seems OK, put it in the raio and key the radio for a bit to try and use up some battery power.... then check it again and see if it has dropped drastically. Your problem has to do with power... the first link in the power chain is the battery... check that out... then go to where the battery makes contact with the radio and make sure thats good.... inside the radio there will be a fuse but if thats blown you will get nothing... then the power goes to the switch. Battery... contacts...fuse... switch... that how the power initially gets into the radio. Most of these problems are battery related so I would check that first. If the battery does not have enough power when you transmit with the radio the radio will shut down.... turn off. If its not getting enough current the voltage will drop and once it gets low the radio shuts off. Usually with commercial stuff you will hear a "beep" when this happens. Your problem might be power related... theres alot you can check.