Batboard

I have a customer that purchased two Motorola Elite UHF portables about maybe 2-3 years ago. Shortly after the purchase the radios where just stored in a drawer and where not used for a long time. They are nowadays still in brand new condition, even with the transparent protective tape still on the display window. Recently the customer wanted to use the radios, and it turns out none of the two would even power up. It was assumed that the batteries might be dead from a long storage period in which the radios where never put on the charger, but after successfully charging both batteries, the radios still will not power up. No sound, nothing on the display will come up to indicate any error. Not even the slightest sign of life.

Needless to say the radios came back to be serviced, and we checked the usual suspects: the internal fuse, battery voltage and contact integrity or corrosion, etc, but everything was ok. So upon further check we noticed that the internal Lithium batteries had a low voltage, one was at 2.5v and the other read 2.8v. We proceeded to change both of the internal batteries, but the radios would still not power up. Then we proceeded to troubleshot any possible faults in the initial power up chain, and confirmed that everything between the MECH_SW_B+ input at R447, Q403, CR440, Q405, and finally Q400 and TP406 (+SWB+) are all working as expected for a short (pulsed) duration, where TP406 will raise to battery voltage level of about 7v and change, and then drop back to zero. BUT the only thing missing is that pin 37 from the U404 ASFIC chip always stays low, so the radio never successfully turns on.

I suspect that the problem might be due to corrupted firmware and/or codeplug data due to the Lithium batteries being low on voltage, so upon the initial boot up the ASFIC is preventing the radio from powering up because either the firmware or the codeplug do not pass the initial checksum test. Or could it be due to a faulty ASFIC? Please bear in mind that these radios where barely used at all, and both where put in a drawer at the same time, under the same conditions, and are now exhibiting the same fault. My understanding is that an ASFIC might go bad only under maybe a handful of circumstances, but for this to happen on both radios and at the same time? Seems like too much of a coincidence.

Any thoughts and recommendations would be greatly appreciated. Thanks in advance.

Alex

Is the reference oscillator running? Sounds similar to the problem Pro series radios have when the 16.8MHz oscillator dies.

Thank you for the input. I will check the ref oscillator for activity, but to be honest I would have trouble thinking that both radios have exactly the same problem where this oscillator just stops working out of the blue and at the same time. What would make this oscillator stop? Probably the xtal going bad? Radios where never dropped or abused. Just sat quietly in a drawer for a long time. Will report back asap to run the tests, but appreciate any further suggestions. Thanks.

As a follow up, I forgot to mention that there is actually a third radio (also a PRO Elite UHF portable identical to the other two) that has the same problem that it would not power up. It came to the shop with a broken flex between the front panel and main board, and since it took a long time to get the replacement part it was also stored for about a year, without the main battery attached, and once the flex was replaced it would not power up anymore. The Lithium battery in this radio still reads 3.0v so should be fine. Exactly the same problem as the other two radios.

jackhackett wrote:Is the reference oscillator running? Sounds similar to the problem Pro series radios have when the 16.8MHz oscillator dies.

I just realized, how would I be able to test the oscillator if the radio does not power up?

I know in the CDM mobiles the oscillator will run without the radio being fully powered up and I can use a sniffer probe on a service monitor antenna port to detect the signal, I haven't dealt with that model portable so I'm not sure how it's done in them.

You might try to see if you can pick up the 16.8MHz signal when you first turn the power switch on (during that 'short pulsed duration' when the other voltages come up). If you can detect it, that would rule out the oscillator.
I've seen it go bad in CDMs that were subjected to too high a temperature, such as mounted right under the heater vents. I suppose excessive cold might also affect them. Were the radios in a temperature controlled area?

The symptoms you listed sounds a lot like what I see on the CDMs, you get some voltages like it wants to work, but the micro doesn't see the signal and won't allow the radio to turn on.

Hello,
If the Elite radio is the same platform as the waris series portables, the problem is most likely the Flash memory chips.
Programming gets corrupted, radio never turns on.
VERY common problem in a lot CDM or Waris portables.

The symptoms you describe are identical to failures in the CDM and HT750/1250/1550 series.

Good Luck
Steve