XPR-4350 getting extremely hot

[zsauve]

I recently replaced a GM-300 radio with an XPR-4350 and mounted it in the Astron power supply that was used with the GM-300. The radio is extremely hot to the touch. The radio isn't being used for transmit, rather it is hooked up to our voice logger and is just used for receive.

Is it normal for the radio to get extremely hot in this situation?

 

[chief21]

If I understand your post, the radio is actually mounted to the power supply (ie - base station configuration). Can you tell if the heat is coming from the power supply itself or the radio only?

 

[zsauve]

If I understand your post, the radio is actually mounted to the power supply (ie - base station configuration). Can you tell if the heat is coming from the power supply itself or the radio only?

Sorry if I wasnt clear, yes the radio is being used as a base station configuration. The heat is definitely coming from the radio. I took the metal hood off the base station that mounts on top of the power supply and radio and it seems to be helping with heat dissipation.

 

[N4KVE]

Sorry if I wasnt clear, yes the radio is being used as a base station configuration. The heat is definitely coming from the radio. I took the metal hood off the base station that mounts on top of the power supply and radio and it seems to be helping with heat dissipation.

Shouldn’t happen. My 4550 is in the same power supply with the shroud, & has been on 24/7 since 2012. Not even slightly warm. Checked the voltage of the supply? 13.8 volts?

 

[XTS3000]

I’ve seen this issue many times on Motorola mobiles that come in for repair. In all cases where the radio gets hot just receiving, the final output PA MOSFET was bad.

When a PA goes bad, it can either blow like a fuse, or short out. It sounds like the PA in your radio has shorted out, causing it to generate excess heat.

First, check the DC voltage from the power supply. I’ve seen many power supplies go bad and output 24-28 volts when it’s regulation circuit goes bad.

If the power supply is outputting proper 12-14V, then measure the current draw going to the radio. When receiving only, it’s current draw should be 0.300-0.540 amps. Anything higher than that, suspect the PA is blown. Check the RF power output on a watt meter/service monitor. I’d bet it’s RF output is rather low.

 

[MTS2000des]

What he said.

Sounds like a bad PA.

I have several 4350/4550s and 24/7 they stay on with no TX duty cycle they are barely warm to the touch. Put an IR thermometer on mine on my desk and it's hottest part wasn't the PA heat sink but behind the display, around 85f.

They do get quite hot on TX full power but that's any dash mount compact mobile. RX shouldn't be turning your desktop station into an oven.

 

[cmdrwill]

Bad RF Power Amp. Leaking FET, common problem.

 

[zsauve]

I’ve seen this issue many times on Motorola mobiles that come in for repair. In all cases where the radio gets hot just receiving, the final output PA MOSFET was bad.

When a PA goes bad, it can either blow like a fuse, or short out. It sounds like the PA in your radio has shorted out, causing it to generate excess heat.

First, check the DC voltage from the power supply. I’ve seen many power supplies go bad and output 24-28 volts when it’s regulation circuit goes bad.

If the power supply is outputting proper 12-14V, then measure the current draw going to the radio. When receiving only, it’s current draw should be 0.300-0.540 amps. Anything higher than that, suspect the PA is blown. Check the RF power output on a watt meter/service monitor. I’d bet it’s RF output is rather low.

Thank you to everyone who replied to my question. The power supply was actually bad. Once I swapped out the power supply, the radio cooled down substantially and everything is working as it should.