CP185 intermittent tone at power up

[tropiradio]

Hey has anybody encountered this?

This is a VHF CP185 radio with display and limited keypad. When the radio powers up all seems normal, the firmware version is briefly displayed on the screen, and then the channel number. Then almost immediately a "too-too... too-too..." two-tone sequence starts sounding continuously and the LED flashes red in unison to the tones. Needless to say, radio does not receive or transmit.

I recall in the past I was once able to fix this kind of problem on this model radio by just reloading the codeplug and it would be solved, but that is not helping in this case.

Checked the inside of the radio and the board is clean, so not a case of internal corrosion. Other than the two-note tone the radio gives and the red LED flashes no other indication of a problem with any error codes on the display which I would think might be the case for a problem related with the microcontroller. I also disconnected the flex between the front keypad/display from the main board just to rule it out, but still the same issue. Also verified that none of the front keys are stuck.

Given that the radio might have taken a fall, I checked both crystals, the 7.37MHz for the controller, and the 3.57MHz of the audio processor, and both signals are present.

Any idea where else to start looking?

 

[tropiradio]

Update: the issue seems to be related to the loss of the 12.8MHz from FL701 the master VCXO oscillator. As a matter of fact while the main PCB is off the radio chassis the oscillator will mostly start normally and radio works. But if I press down a bit on the metal case of the oscillator I can see the 12.8M signal go away or greatly drop in amplitude, and right at the output pin of the oscillator can. The 5V supply to the oscillator is steady, as is the voltage at the Vcont input pin. Ground also seems stable.

Swapping out the FL701 oscillator (supplier: BGTech, Supplier PN: 8289012R80010, and description being "SHINSUNG, VCTCXO,12.8 MHZ")
should most probably solve the issue, however about a year ago I tried to get this part from Motorola and they said it was discontinued. However the newer generation EP350MX radios (LA version of the CP185) still uses the exact same part, but perhaps the part number was updated. And so far I have been unable to get a detailed service manual for that newer current production version of the EP350MX radio in which some parts have been clearly changed/updated and in general its also very clear that some areas of the main PCB look different compared to the older original version.

Does by any chance anyone have an EP350MX detailed service manual newer than 6878422A01-B or more recent than August 2009? A newer CP185 detailed manual would also probably help, although I understand that the NA version of the radio was discontinued long time ago. In any event that manual version/year is the latest one I have, but again the part number shown for the FL701 oscillator seems to be no longer available at Motorola, or so they say.

Checked the manufacturer website for SHINSUNG and they still manufacture these type of oscillators, but the one of the size of the part I need to replace is no longer listed, only much smaller versions. Also tried looking online for the inscription that the oscillator has on it, VX-F4-2.5F1 but again no useful results. BGTech listed as the supplier does not seem to exist anymore.

 

[tropiradio]

This is what the part looks like on the PCB. Its a SMD and measures about 10mm x 11.5mm.