APX 4500 Refuses to transmit more than half a second and beeps. Need help

[Mogley]

Hello, I was sent to pick up a faulty radio a while back. It refuses to transmit for more than half a second and just beeps.

The radio does this on both trunking and conventional. I've sent it out to Motorola for repair and they sent it back repaired but it is still doing it. Could it be something stupid like TOT being set to something stupidly low? Is the board fried and needs to go back to Motorola yet again?


Thanks in advance. Video attached.

 

[MEDIC135]

Hello, I was sent to pick up a faulty radio a while back. It refuses to transmit for more than half a second and just beeps.

The radio does this on both trunking and conventional. I've sent it out to Motorola for repair and they sent it back repaired but it is still doing it. Could it be something stupid like TOT being set to something stupidly low? Is the board fried and needs to go back to Motorola yet again?


Thanks in advance. Video attached.

It’s not a faulty anything, that looks like the programming is set to “receive only” for that channel.

 

[Mogley]

It’s not a faulty anything, that looks like the programming is set to “receive only” for that channel.

I've programmed receive only. The red TX indicator will not light up at all if it is programmed to RX only.

 

[MEDIC135]

I've programmed receive only. The red TX indicator will not light up at all if it is programmed to RX only.

Can you confirm the radio isn’t programmed to that since you stated that you were sent to pick up this “faulty” radio?

 

[Mogley]

Just looked at the codeplug again, none of the personalities trunking or conventional have receive only personality checked.

 

[lorenzolrom]

This just looks like conventional TPT, it's looking for a repeater tail.

8CALL90 is set up as a repeater by default, so if you don't get the P25 repeater tail you get BONKED.

 

[MTS2000des]

Yep, that is exactly what you get- except 8 CALL 90 is analog and the TPT only functions on digital conventional. Something else is wrong here.

 

[n3obl]

Is the power supply strong enough to handle the transmit load?

 

[Mogley]

I've tried two different power supplies at 13.8 volts.

 

[mmckenna]

I've tried two different power supplies at 13.8 volts.

What is the amperage capacity of the power supply?

 

[Mogley]

It is an astron variable power supply cuz I tried it on. It was set at 1 amp. The power supply that was at the station that I pulled it from is one of those basic Motorola plug in the wall. Looks like an oversized laptop charger power supply

 

[KevinC]

It is an astron variable power supply cuz I tried it on. It was set at 1 amp. The power supply that was at the station that I pulled it from is one of those basic Motorola plug in the wall. Looks like an oversized laptop charger power supply

Those Motorola ones are prone to be crap and 1 amp ain't gonna cut it for TX on the Astron.

 

[MTS2000des]

The Motorola PSUs are either 7.5A continuous to 15A intermittent, the 1 amp ain't gonna cut it for transmit. There is your problem.
Spec sheet shows 850ma standby, 3.5A at full RX volume and TX current draw at full power 13A for VHF, 11A UHF R1/2 and 8 for 7/8/9.

 

[Mogley]

Alright I will switch it to 8 amps and see what happens

 

[mmckenna]

8 amps will ~probably~ be sufficient for a 35 watt radio. If you can, set the radio to low power on that channel before testing.

Insufficient current will usually cause the radio to power down/restart, but it could explain this one bonking on you.

Better yet, use a 15 amp supply and you won't have any issues.

 

[K2NEC]

What's your antenna setup like? I've heard of radios shutting down like this when the SWR is too high.

 

[Mogley]

What's your antenna setup like? I've heard of radios shutting down like this when the SWR is too high.

I had a dummy load connected to it

 

[n3obl]

As stated 15 amps should be minimum for a dash mount radio.

 

[KevinC]

Please don't take this wrong, but I sure hope you aren't station 1's primary technical support.

 

[Mogley]

Please don't take this wrong, but I sure hope you aren't station 1's primary technical support.

There's two guys technically. it's gonna get sent to depot. Put it on 15 amps and it's still misbehaving.