Uniden Atlantis VHF radio problem

Howdy Ray.....I don't know your radio specifically but would suggest initially determining whether you are looking at a bad power circuit connection which fails under transmit load OR whether there's an abnormal heavy current condition occurring during transmit. Does the receiver otherwise work ok? One place you might look is at any switching contacts part of a connector for external power or for external charging. I've found many times particularly with the coaxial type power connectors that when they use a contact to disconnect the radio during charging, that this will fail under load.

You didn't mention whether you experienced a heavy current condition while testing with your bench supply so I tend to think the situation is a poor connection. IF it seems that you're into a heavy current condition during transmit, you might check for a shorted stage....disconnect power at the final for example to isolate that and work backwards.

Hope this helps get you started.

Gord VE1AJF

Yes, all functions work fine except for the battery pull down problem. If I pull the battery real quick and test it, it's not down for voltage much and recovers to full voltage in a few minutes so maybe the battery state LED display is just haywire. It has 2 transmit settings, 1W and 5W. The 5W is good for about 5 seconds and then the readout gives a blinking error and transmission stops. It does transmit well enough to another unit across the yard on the 1W setting. It's difficult to get to the battery contacts as they are a recessed, spring loaded affair and the external power is the typical 1/8" dodad popular in miniaturization these days.

It's a waterproof hand held for use in salt water environments with some type of brown paste on all the connections and pass throughs.

No, I didn't see any indication of a big load. Usually the bench supply will groan and the voltage meter dips if there's something exciting about to happen. Now that I have it open there really is nothing to test or fix or examine inside- just a maze of surface mount resistors and a central proprietary chip half the size of a postage stamp. Probably just good for the CG weather channel now.

Thanks, Gord.

This sounds like normal behavior from a dying battery. NiCad, NiMH and alkaine batteries all act this way.

Since it works for a few seconds, it's likely that the batteries have not shorted or leaked. I built a good deep cycle discharger from a five volt relay and a large (10 Ohm 10watt) resistor. The relay coil was in parallel with the resistor, and it's contacts when activated connect them to the battery.

A push button across the contacts to activate it and an LED with a current limiting resistor completed the device.

You push the button and let the battery discharge. When the voltage gets to low to keep the relay closed, it stops discharging but the battery does not go too low to be damaged.

If it is a NiCad or NiMH battery a few charge discharge cycles should bring it back to normal. This assumes that the batteries have not leaked or been damaged in any other way.

Note that this should NEVER be done to lead-acid or Lithium batteries.

While many experts have claimed that NiCad and NiMH batteries do not have a memory effect, I used to get lots of NiMH batteries or cell phones as gifts when they were near dead. A few cycles in the reconditioner and they were back to normal.

This is almost seven years later, and I'm still splitting the packs apart and using them to rebuild ham radio battery packs.

Lithium Ion battery packs can be "fixed" by sitting overnight in a freezer, but it has NEVER worked for me. Freezing ultrasonicly welded NiCad packs makes them easy to split open and replace the batteries.

Geoff.

Right, but I get the same result from running it on a bench supply.

Great idea. thanks.

Hmm, I have some power tool batteries I was wondering how to take apart. Thanks.

(works for a few seconds and stops)

Where? The DC in jack may be only for a charger. In order to pass saftey regulations, the current may be limited on the DC in jack.

This would prevent the radio from "blowing up" if water got into the DC in jack and the batteries discharged through the radio very quickly.

For example, I once discussed the subject with the product manager of a handheld GPS unit. I suggested that they make sure the battery charging contacts where current limited so that shorting them would not cause damage to the user or the battery. He had never heard of such things.

I was involved with the design of a handheld gaming device. We had specificly designed it so that if the battery on the unit or a spare in your pocket got wet or contacted keys or loose change, nothing bad would happen.

I think it is safe to assume that while not everyone does this, some companies do.

Geoff.

I removed the battery and hooked jumpers from the supply to the battery contacts so there's no battery involved for the test.

Good idea.

Thanks.