NX-700 random beep

[fire_master_21]

I have been asked by a neighboring department to look at this problem radio. The radio was in an ambulance and worked great for about 3 years. The radio recently developed a random beep emitting from the speaker. I have checked all wiring and voltage on the ambulance and all is well. I replaced the radio and the new radio is working fine in the same ambulance. I have had the trouble radio on a Astron power supply, for approximately 3 weeks with no signs of the beep until last night. The beep is short and consistent about every 8-10 seconds before the next beep. The beep is only through the speaker and never transmitted.

Things I have tried already,

Newer power supply

Rebuilt codeplug

reloaded firmware. (I can't remember what version right now what it has as I am at work and the radio is at home.)

This is used on an analog system, with no signaling being used, no (NXDN, MDC, or 2-tone)

Any ideas what it could be or is a trip back to Kenwood in order?

 

[mmckenna]

I think if it was mine, I'd put it on a service monitor and see how it was doing. The beep may be the VCO unlocking, may not.

Since it's so periodic, it might be on the end and just randomly wander out of lock.

Could also be an intermittent component.

Does heat/cold affect it?

 

[fire_master_21]

Now that you mention it, it was hot in my garage where I moved it last night, while I was working on other projects. Prior to moving the radio in the garage it was inside the house, where it was about 75 however the garage was about 100.

 

[mmckenna]

I'd suggest putting it back in your house and see if it stops.

While high heat shouldn't necessarily be an issue, if there is a marginal component or it's on the edge of VCO lock, that could certainly explain it.

 

[k4ktr]

I bet the beep is related to the scan just by chance is scan on or off note scan can beturned on even tho there are no ch in the scan list that will cause the beep

 

[fire_master_21]

Definitely not a scan issue. This problem happens when parked on any channel and not in scan mode.

 

[AD0TY]

I agree with mmckenna. I think the radio is drifting out of lock for some reason. If it regularly happens on a specific frequency, program that into the radios test frequency list and then get in test mode and observe the receive assist voltage when it is acting goofy.

 

[westcoaster]

Try pulling the front panel apart that has the keys (volume, channel, etc.)

check for stuck buttons, do a thorough cleaning on the rubber buttons, take an alcohol pad and clean off the carbon pucks in the rubber keys, clean the corresponding PCB.

My thinking is if the control tones are on, key that is not programmed or volume control....

I have that once in a while on telephones I service.