Batboard

We have a UHF P1225 (16ch) that came in with a frequency error in excess of 8KHz. Our junior tech (and I use that term generously) decided he could correct that in the service menu by adjusting the TX frequency warp all the way to the extreme, rather than asking a senior tech. The result is a radio that now doesn't turn on - sort of. When 'turned on', there is no confirmation beep, no functionality at all and the RSS can't see the radio (it comes back with the check cables and power message), yet you can hear the noise floor of the audio amplifier in the speaker, albeit at very low volume. This and a check of the power trace to the microprocessor tells us the power circuit is fine, though obviously there's another problem that led to an 8KHz frequency error in the first place. (For those of you about to ask; we are powering the radio with a known good and regulated 7.8VDC linear PSU.) The RSS is v3.2 ('D') on a Win98 machine.

We figured he adjusted the VCO so far out of tolerance, the microprocessor sees a major fault and thus won't function. Anybody have any knowledge or thoughts on a remedy, other than sending it to M or using as a doorstop?

Thanks,
Henry

Henry,

You have a bad Y201 synthesizer crystal. Motorola will not sell it to you, but you can buy them from International Crystal. Or you can just take one off a junk board.

If you buy one from ICM, I would warp it after you install it, then let it run for a day or two, and warp it again if you need to, just to make sure it didn't drift after the first alignment.

Tony

So once the new crystal is installed, the microprocessor will allow the radio to power up fully?

Henry

PRR wrote:So once the new crystal is installed, the microprocessor will allow the radio to power up fully?

Henry

Yes.

Before you do anything however, inspect the leads to make sure one or both may be lifted from the board a bit. A solder fracture there will render the radio dead, and may even cause drift as well.

Thank you very much Tony. We'll give it a go.

Henry

PRR wrote:Thank you very much Tony. We'll give it a go.

Henry

So Henry, how did you come out on this one?