VX-8R overheats when TXing and connected to DC power

[j-squared]

I plan on calling Vertex, but I was wondering if what your experiences are with the following:

1. Unit overheats when transmitting while connected to the DC power
2. Unit power-cycles when transmitting when connected to AC power

I have the LCD set to display the internal temp. It's pretty hard for me to see clearly when driving, but I believe I saw 158F degrees. I usually have the radio connected to power in the car. I am using an externally mounted Comet SSB-1.

I consider these two things to be major faults.

Thank-you,
Jerald Josephs
KI6OIF
Santa Clara, CA

 

[Moleculo]

This little HT gets pretty hot in your hand while TXing for longer periods. However, this isn't anything unusual compared to other small HTs that I've owned. These small little radios just don't have enough mass to make an effective heatsink. They also don't employ any fans. That's just the way little HTs are.

Regarding this:

Unit power-cycles when transmitting when connected to AC power

If you look at the bottom of the wall wart, you'll see that it only provides 0.5 amps of current. However, the manual indicates that the radio requires 1.7 amps of current to transmit a 5 watt 2 meter signal. That's why the radio turns off when you TX while charging on the AC wall wart - the transformer in the wall wart isn't designed to supply the current required to TX. What you're seeing is normal, not a defect. However, if you are charging with the DC cigarette lighter, the radio is able to draw sufficient current, so you can TX while charging.

Both issues that you've described are fairly common with HTs.

 

[j-squared]

Thank you for the info. I guess I am only left with the observation that the HT is beeping at me when it reaches a high temp and some of my transmissions failed when they had succeeded before.

Perhaps the conclusion is that the unit should not be used for extended transmissions at full power when connected to DC power. I was hoping to use it in place of a mobile unit in my truck.

Thanks,

Jerald

 

[Moleculo]

I guess I am only left with the observation that the HT is beeping at me when it reaches a high temp and some of my transmissions failed when they had succeeded before.

Are you sure that you're not triggering the transmit Time Out Timer? By default it's set to 3 minutes of continuous talk time before it beeps at you and kills your TX. It's menu 102 - TOT (page 127 in the manual). I've triggered this lots of times, but I've never experienced the unit killing a TX because of heat. I'll look through the manual a bit for this.

 

[ke7vvt]

Ya-Moley is right, check the TOT.

When I have mine plugged into the car charger the radio gets really hot when it is charging the battery. It usually stays just warm if the battery is fully charged and is just monitoring, but as soon as the battery needs to be charged the whole radio gets quite hot. The car charger is a 2.0A output device too, which is the main difference between it and the 0.5A wall charger.

I figured this temp thing was not good for the radio or the battery, so I just remove the battery when it is plugged into the car charger. Try that and see if the radio is getting hot from transmitting or if it is because the battery is getting hot from charging.

I am interested in what effect this has, if you try it out please post the outcome.

 

[surfpaddler]

I recently ran mine on a trip from florida to texas. With the radio in beacon TX mode, GPS on, Display on continuous, smaller capacity battery (original eq.) plugged in to the car power, Beacon tx every 3 mins, The radio got so hot that the display contrast became unstable to the point that the radio was un-usable. I didn't think to check the temp(oh well) I did shut the radio down untill it had cooled off. Never ran it in that configuration again. I ran on battery power no charger. I have three batteries so I did not need to recharge any for the rest of the trip while in the car.

Oh I also had the bluetooth running. I have yet to run the headset dead. I have the mono version.

 

[ke7vvt]

I think that the main source of heat comes from the high current source charging the battery. The car charger charging the battery is what makes the radio get hot, if you take off the battery the radio will not get hot. I assume that this would be the same if you are powering it with your own external bench power supply.

Since the radio is on it is must be drawing something from the battery and this causes the charging circuit to kick on and ask for the full 2.0A from the car charger. P=R I^2 heating is what is going on. The wall charger is, recalling from memory, 0.2A. The "defect" here is that it would be nice if the radio completely ignored the battery if it is plugged into an external source, other than to charge it.

There is a post about the the screen here, http://www.worldwidedx.com/handitalkies/40392-vx-8r-anti-glare-display-question.html#post171957, that happens when the radio gets too hot.

So if your going to use the radio from an external power supply, you should remove the battery. It will be OK to charge the battery while the radio is off or on, but it will get hot either way, but maybe not as hot if the radio is off and just charging. That has been the downside for drop in quick chargers, they allow the battery have "a lot" of current to charge and it can wear out the batteries quicker. From experience with the 8R chargers, the car charger is the one to watch out for. The drop in charger does not make the radio any warmer than the wall wort (as supplied) charger while charging. Here are some older posts about the chargers, http://www.worldwidedx.com/handitalkies/34438-issues-charging-vx-8r-battery-3-ways.html and http://www.worldwidedx.com/handitalkies/34019-vx-8r-operation-cd-41-charger.html.