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Thread: APX 7500 is it worth getting a new circuit board?

  1. #1
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    Default APX 7500 is it worth getting a new circuit board?

    Hi
    Well 2 weeks ago I was able to acquire a 7500 mobile in the single band of 700/800 only. It had seen better days but still worked very well as well. Updated the firmware to V15.00 also. Well sad to say wife accidentally knocked the radio off the table onto the floor and when i turned it on to see if it worked , it would start up and scan like it should but it would not receive anything at all. Opened it up and a small silver conductor made by MCL had broken lose. If you open the radio up and looking at it from the head twords the back of the unit right up front in the middle right below the nice silver box there is where the semiconductor used to sit. So my question is this is it worth paying for a new circuit board since it is a single band unit only or should i just go ahead and get a new used 7500 unit?
    I did call mother moto and they said they do have the circuit boards in stock and the cost would be $600 to replace it plus i pay shipping both ways..
    So what do you all think? is it worth paying the $600 since the unit is now EOL and single band only???
    MCDoug


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    Do you have pics? Are you not able to resolder/replace the part?

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    If it's a 7500 it should have a secondary band you can have enabled through a flash upgrade.
    KMA 367

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    Not on the 7500. On the 8500 I believe thats true but for the 7500, you'd need a whole new RF board with the two bands you want then enable it in the flash.

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    Quote Originally Posted by ndp View Post
    If it's a 7500 it should have a secondary band you can have enabled through a flash upgrade.
    Not necessarily. Many of em were built and shipped with a single RF deck, especially consolettes. If it only reports single RF band in service mode, youve basically got a 6500.

    This radio is well worth a trip to the depot, do it *soon* before the dreaded troubled parts advisories start on em.
    Last edited by jason; 1 Week Ago at 01:56 AM. Reason: Formatting

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    20200626_083541.jpg
    This is the picture of the part that broke

    20200626_083748.jpg
    20200626_083621.jpg
    This is the picture of the part where it was before it broke off

    I am going to try to see if I can fix this. I have done things like this in the past starting when I built my first HeathKit shortwave radio when I was 14

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    If the pads on the PCB weren't ripped off, I've got a good shot a fixing it for you. If the pads were ripped off, it still might not be hopeless. PM and we can discuss.

    I agree with Jason that this is truly worth getting repaired.

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    MCL? Looks like a mixer or amp? It will indeed "buff out".

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    Here are a couple more pics of the filter that I took with my webcam a few minutes ago
    Picture 6.jpg
    Picture 5.jpg
    Picture 4.jpg

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    You probably need a hot air station to get that back in. Someone here might be able to help.

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    I agree with wiredwrx that you will probably need a hot air station. The way that I would do it is use reflow solder to tin the pad, put the part over the pads, protect the surrounding area, and then hit the part evenly with the hot air. The part will suck down. Not easy with that part but not impossible and definitely worth a try. I'm surprised that the part came off the board. That must have been one heck of jolt.

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    yes i had it sitting here on my work table and wife accidentally knocked it to the floor and it landed on its side. Needless to say i was not happy but accidents do happen as well.

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    That part has notches corresponding to each of its pads. Assuming that the pad has enough meat left to conduct signal, simply wet each of the pads with a soldering iron, place the part on the PCB and use a fine tipped iron to melt the solder already on the pads to the PCB. Add a bit of solder if necessary. You don't need a hot air bonder to do this and the part placement does not have to be perfect. If one side is bumped up, just flow a bit more solder underneath.

    The worst would be if the part is damaged and you need to spend $20 at Mini circuits. I would look up the part and its internal wiring if possible so you can ohm out the leads if one of the pads is ripped. Usually these are transformer coupled so there will be a short or small resistance from each RF/IF/LO pad to ground.

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    FYI the part number for this item is HJK 870H-1 and i have not been able to find it anywhere. I have tried mini circuits and so far no joy. Does anyone have an ideas where I could find this part? Here is the complete numbers on the top of it
    MCL 0 1048
    HJK 870H-1
    0+

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    It's a Mini Circuits part. The HJK series for a mixer/LO with a top freq of 870 MHz (makes sense since this is a 7/800MHz APX).

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    Does the part "ohm out"? the main RF/IF/LO pads should all show continuity to ground because it is a balanced mixer with transformers. If so, solder that sucker in and try it out.

    If its broken, contact MCL for a spec sheet then cross reference with their other parts to see the frequency range, insertion loss etc. It could be a stock part that got a special number for Motorola, because Motorola will probably mark it up in price. Maybe MCL will suggest a replacement. You might have to but from Digikey or Mouser to get single unit pricing.

    My gut tells me its is still good.

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    Quote Originally Posted by romanrobles View Post
    It's a Mini Circuits part. The HJK series for a mixer/LO with a top freq of 870 MHz (makes sense since this is a 7/800MHz APX).
    The 0+ probably means 0 dBm LO injection.

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    It's a custom part for Motorola. Mini Circuits wont' sell it to you, and neither will Moto.
    Last edited by romanrobles; 3 Days Ago at 03:37 PM.

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    with the 7500 being eol you would think mother motor would not care but nooooo they want the $$$ while they can... they quoted me a price of $600 to do a basic circuit board replacement..

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    I wonder if their is any part that mini circuits or some other suppler sell's that could be compatible with that part to make it work???hmmmm

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    It is just a mixer, and likely a 0 dBm one. Determine the RF IF and LO Frequencies and you are halfway there. Select the best conversion loss , the package style and press BUY.

    Are you sure the part is damaged? Ohm it out, Install it already and test it.

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