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CDM 750 and cdm1250 wont power up.

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Satelite
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Joined: Sat Aug 12, 2006 10:43 am

CDM 750 and cdm1250 wont power up.

Postby Satelite » Wed Sep 19, 2018 3:53 pm

Hello
Ok lets just talk about the cdm 750 for the moment.
Its a uhf in the 463 meg band and 40 watt version.
When I attempt to power up the cdm750 mobile by pressing the front button it doesn't power up
How ever this mobile does have a phone dtmf pad mike on it and the dialer pad does see voltage in the rubber numbered phone number pad that's the normal green color and this is with radio push on off button pressed to turn on and if you press it for off the dialer pad stays bright green normal lit up color.
I do have 13.6 volts dc on various parts of the bd but no schematics to verify any of them being correct plus other voltages as well that likely could be correct too. ( Don't know don't have schematics.
Its like theres voltage to mic dialer pads on mic jack but not getting to start up circuit .
Ok further testing does show a 5.1 vdc at push button on off and when pressed does sow 4.8 vdc on other side of the push button on off sw.
So on off sw has 5.1 vdc supply and pressed for on shows 4.8 vdc on opposite side and when buttons realse the voltage is no longer at opposite side for power on but I suspect that's correct other than is 5.1 vdc input correct and does 4.8 vdc output sound right ?
Another question is there by chance a on board fuse like you see in the maxtracs gm300 mobiles on the logic bd I should be aware of to check ?
And theres no 20 pin option plugs in either of these radios nor do I have any for test but does the cdm radio need the option plug installed to operate on and so forth ?
Neighter radio was set up for ignition sense and I did try power to the pin on the other cdm1250 and no change same no power up.
Im hearing the flash program in the cdm series has been a common problem and yes i do have a prom reader / burner and can get the prom but im not going to be able to initiate the prom with out the cdm program or lab ware and dont have them eigther and if thats the problem then im going to have to say im not willing to go that far with a radio that has been so dang unreliable for me and theyll be sold parts with info known and or boat anchors.
Depot fee of 150 plus is not an option when i can purchase a narrow band gm300 or m1225 and have no more issues with flash programs and various version tha M screwed up.

Satelite

Satelite
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Re: CDM 750 and cdm1250 wont power up.

Postby Satelite » Wed Sep 19, 2018 4:03 pm

Hello
Just adding info.
These two cdms are mounted in tractors used for corn growing operations so in a farming tractor scenario.
Both radios powered up normally from day one new and was never ignition sense.
And worked fine up until say Monday it worked Tuesday dead but each other died obviously many months apart not like within days and were swapped out with narrow band gm300s and thrown in shop corner by the farmer and now dup out for possible repair and use.
Its possible they had 20 pin plugs that fell ouyt disabling the radios so did ask above if they were needed.
On gm300 mobiles the plug not the same as the dm plug I know but not needed to power on but needed for audio unless pins jumpered.
So does the cdm series need the 20 pin option p[lug installed to power on ?
Satelite

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jackhackett
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Re: CDM 750 and cdm1250 wont power up.

Postby jackhackett » Wed Sep 19, 2018 6:52 pm

A common cause of Pro series radios failing to power up is a bad 16.8MHz reference oscillator, from the symptoms you mentioned that sounds like what you've got. For that problem they replace the whole main board, the oscillator is not field replaceable.

Whether or not a CDM needs ignition sense to power on depends on how it is programmed.

fineshot1
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Re: CDM 750 and cdm1250 wont power up.

Postby fineshot1 » Thu Sep 20, 2018 5:39 am

Look over this thread and if the emergency power up does not work it must be the reference oscillator failure issue

viewtopic.php?f=1&t=107693&hilit=CDM+Emergency+Power+up
fineshot1
NJ USA

Satelite
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Re: CDM 750 and cdm1250 wont power up.

Postby Satelite » Thu Sep 20, 2018 4:59 pm

Hello
After reading jackhacketts reply and then my further testing im inclined to believe the 16.8 oscillator crystal is defective.
Ok its not available from Motorola out in the field repair and a depot repair item.
But short of that im now thinking what if I removed a 16.8 oscillator crystal from a old no longer used GTX 800 MHz trunked portable and put that in the cdm750.
I suspect it would power up then figure out how to go about calibrating if needed and or if id be able to just warp on freq and make this a base station kept in same room temp so temp compensation values wouldn't be so drastic ?
I don't have the cdm 750 uhf manual but the gtx 800 privacy plus manual shows the 16.8 MHz oscillator as part number 5102845C11 and its shown as available not a depot item but ill rob mine out of a used no longer needed working gtx 800 MHz pp trunking portable if itll work.
Can anyone put up the part number for the dm750 16.8 MHz oscilaror crystal and see if by any chance in heavan ( You thatought I was gonna say HELL didn't ya :-) ) They by chance they match part number ?
Satelite

Satelite
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Re: CDM 750 and cdm1250 wont power up.

Postby Satelite » Thu Sep 20, 2018 5:01 pm

Hello:
Forgot to mention I too tried the Emergency wakeup pins 9 and 10 with no power up still dead radio with power present in control head and on various places of the circuit bd.
Satelite

Satelite
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Re: CDM 750 and cdm1250 wont power up.

Postby Satelite » Thu Sep 20, 2018 5:10 pm

Hello:
Just found these on ebay .
Already tempature compensated and external pcs for setting the voltage to calibrate on freq per the info.
Should be the ticket id think . WWW.EBAY.COM Auction search number 200407004018 Cost $9.99 each shipping $5.50
Satelite

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jackhackett
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Re: CDM 750 and cdm1250 wont power up.

Postby jackhackett » Fri Sep 21, 2018 11:16 am

I have found some part numbers for these oscillators, and MOL shows them as available. I don't remember where I saw that they weren't field replaceable, so I may have been given some bad information on that. Here are the numbers for what it's worth...

4886182B01 - VCTCXO 16.8MHZ 2PPM TTS05V
4886182B02 - VCTCXO 16.8MHZ 1.5PPM TTS05V

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kcbooboo
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Re: CDM 750 and cdm1250 wont power up.

Postby kcbooboo » Sat Sep 22, 2018 5:12 am

They probably say "Not Field Replaceable" just because of the component density, surface-mount technology, and just not easy to replace with a 40w soldering iron "in the field". Those radios are pretty much "replace the entire board" if there are any problems. There's most likely an industry-standard part you can buy from Mouser or Digikey for far less than Moto's price.

Bob M.

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jackhackett
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Re: CDM 750 and cdm1250 wont power up.

Postby jackhackett » Sat Sep 22, 2018 5:30 am

Yeah, it's not something I'd try to replace without the proper surface mount soldering equipment. It's one of those things with the contacts mostly underneath. You'd probably just end up damaging it if you tried it with a pencil iron.

In the detailed service manual some models show the oscillator on the schematic but not in the parts list. I think what probably happened years back was that I didn't see a part number in the list for the model I was working with, contacted Moto Parts ID, and was told that they weren't replaceable.

Satelite
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Re: CDM 750 and cdm1250 wont power up.

Postby Satelite » Mon Sep 24, 2018 8:50 am

Hello To All That Replied And Much Appreciated.
Jackhackett - You and kcbooboo both are on the same thought path as I read it.
I was able to remove the oscillator without damage to bd but as mentioned the oscillator is soldered underneath and I do have a hot air station with a fine pen solder station as well BUT SO TINY SMALL the oscillator component that im not feeling comfy with a good outcome.
As matter of fact I feel my lucks going to be lower than whale :o if I try.
I haven't bothered to price the oscillator but id bet itll cost a bit more than id care to spend on shall I say trial and error attempting it.
But then again I haven't reassembled the radio for scrap part out to ebay either so still thinking my options and problem is I don't see a better option.
So likely stalled forever possibly unless I get a radio with other issues making robbing parts from this one and its junked.
Satelite

com501
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What radios do you own?: Over 50 - All Motorola

Re: CDM 750 and cdm1250 wont power up.

Postby com501 » Tue Sep 25, 2018 11:56 am

CDMs are dirt cheap on eBay. Buy another one.

Satelite
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Joined: Sat Aug 12, 2006 10:43 am

Re: CDM 750 and cdm1250 wont power up.

Postby Satelite » Thu Sep 27, 2018 10:04 am

Hello:
NO OFFENSE AND MY APOLOGY :-)
Hell no I wouldn't buy another piece of crap cdm.
They've been nothing but trouble.
Still have old gm300 12.5 narrow band mobiles that never dropped dead on me a few had the oscillator crystal go south I had to replaced and calibrate ill admit but never had one couldn't fix as a rule.
No ill just hug my old m stuff that worked well not a visar or cdm as ive seen them just go bad and I do blame Motorola for making unreliable radios now.
Just no wheres dependable as I once knew them to be.
Didn't like the P100 or ht50 portables they had crystal issues and rx howling just didn't stay running without constantly tuning fixing.
Still like the old m stuff like gm300 / radius m216 / maxtracs / gp300 / m100 / M1225 mobiles weren't too bad as an example .
Satelite


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