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Thread: CDM Series Low Band DEtailed Service Manual

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    Default CDM Series Low Band DEtailed Service Manual

    Has anyone been able to find a detailed service manual for the Low Band CDM series mobile radios. The range that I am looking for is 42-50 MHz.

    Motorola does not have one (called support and they could not find one). I asked Parts ID to check for the part number for a transistor and they could not find any reference to that TANAPA number or model number.


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    What a surprise, Motorola don't know how to support their products! Try the obvious place first is beyond them. It's included in the ordinary DSM, see section 7, you can find a copy here http://www.repeater-builder.com/moto...et-svc-man.pdf

    If what you need isn't in there, I have the European version which could be worth a try.

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    The low band (42-50 MHz)radios are not included in this manual. There is some information in the basic service manual but not what I need.

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    Quote Originally Posted by FMTRU140D View Post
    The low band (42-50 MHz)radios are not included in this manual. There is some information in the basic service manual but not what I need.
    Chapter 7 in the manual linked above covers all three low band ranges, including PCB layouts and schematics.
    "The Girl Scouts found several hungry REACT members at the finish line..."

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    [QUOTE=knickerlessparsons;104582]What a surprise, Motorola don't know how to support their products! Try the obvious place first is beyond them.

    With the transfer of customer disservice to Juarez Mexico & the loss of years of expertise in Schaumburg, we are left with a group of people that know nothing about everything.

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    Quote Originally Posted by FMTRU140D View Post
    The low band (42-50 MHz)radios are not included in this manual. There is some information in the basic service manual but not what I need.
    Have you actually bothered to read it? Section 7 has all the low band stuff.

    If what you need isn't there I'm sure people may try to help you, but there needs to be a bit of buy-in from your end.

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    [QUOTE=ppcradioman;104588]
    Quote Originally Posted by knickerlessparsons View Post
    What a surprise, Motorola don't know how to support their products! Try the obvious place first is beyond them.

    With the transfer of customer disservice to Juarez Mexico & the loss of years of expertise in Schaumburg, we are left with a group of people that know nothing about everything.
    I'm with you on that, for us European types it's a call centre in Krakow, Poland, staffed by awfully nice people who are very helpful, in an unhelpful way. When will big companies realise that apologising and saying I am trying to get an answer from our....... isn't customer service, it's an information buffer. Everyone involved knows it's BS, so stop trying to polish a turd. (Apologies if that doesn't translate to Americanese, but I think you'll get the general thrust of my comment.)

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    Here in the USA, I have had many conversations with engineers in Poland. If you are persistent you can work your way through the BS and actually talk to someone knowledgeable. -If you can translate broken English.
    Apparently NOT a radio professional.

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    I flat overlooked the low band part of the manual. I think that this is the first time in 15 years that I have had to work on the low band version.

    Two radios both making less than 60 watts, damaged PA transistors due to running with a bad antenna.

    When I got the radios on the bench, I opened one up and discovered that this radio uses two transistors in the final stage. They were the same part number as used in the VHF radios 48012035001.

    Changing both of them brought the power back up to normal.

    This brings up another question, we are seeing a lot of PA failures using this transistor (LDMOS). If a customer runs the radio into a bad antenna, it is sure to damage the PA and the radio ends up making about 50% of the rated power.

    I am curious to see if others are experiencing the same problems as we are.

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    It has been my experience that low band is a lot more touchy on antenna SWR. A small change in freq causes a relatively larger change in antenna length compared to VHF or UHF (its a logarithmic curve). Many low band installs also have poor antenna mounts or bad vehicle locations chosen (whips touching the frame while moving is common). I suggest a PM of all the antennas to fix any underlying problems this will save you a lot of headaches and complaints about not 'fixing it right'.

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    These LDMOS for the CDMs and the one for the UHF XTLs (110watt) are definitely problematic.
    Apparently NOT a radio professional.