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Thread: XTL2500 XTL2500 R1 UHF 425-470 tx vco mods

  1. #1
    throwed No Longer Registered

    Default XTL2500 XTL2500 R1 UHF 425-470 tx vco mods

    hi all, hope you have all been well! i have a few questions regarding the 425-470mhz TX vco in the Range 1 XTL2500/5000 we are trying to get it to lock up at 480 mhz and are not concerned about losing 425-435mhz TX if we have to , can this be achieved by changing a resistor / adding a resistor or by shaving a little from the end of the tuned copper vco block with a light hobby dremmel ? if anyone could have a quick look at the service manual and give me their thoughts on this it would greatly appreciated.

    many thanks all!
    Christian


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    The R1 XTL covers 380-470 out of the box. It should TX up to 480 with a software mod. Have you even tried yet, before breaking out the soldering iron and sandblaster?

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    I have read other posts in other forums and they state the vco stops working near 477. The vco range can be pulled up by changing r5830 from its current value of 1.3k to a value near 1.5-.17k. The actual value will need to be determined by experimentation but the modification should work. This is basically the same type of modification that was applied to the Astro Spectra series by Alpha to "pull" up the voltage for their R1-R2 split.

  4. #4
    throwed No Longer Registered

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    tried this, it doesnt want to tx on 477 what so ever... and as for the other forum saying about R5830.. this has not been done or been proved to work..the spectra mod uses a resistor in parallel to lower the value of the other to bring the vco lock up ... why would the XTL use a higher value resistor ? dont we want to raise the lock voltage? how can this work by a higher value resistor?.. id like to hear from some ppl who have done a mod to their own radio and had it working... cheers

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    Quote Originally Posted by throwed View Post
    tried this, it doesnt want to tx on 477 what so ever... and as for the other forum saying about R5830.. this has not been done or been proved to work..the spectra mod uses a resistor in parallel to lower the value of the other to bring the vco lock up ... why would the XTL use a higher value resistor ? dont we want to raise the lock voltage? how can this work by a higher value resistor?.. id like to hear from some ppl who have done a mod to their own radio and had it working... cheers
    Try installing a small variable resistor (VR) and adjust/experiment until desired operation is achieved. Then measure the value and replace the VR with a fixed-value resistor.

  6. #6
    throwed No Longer Registered

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    ythanks for the reply mars , i appreciate it greatly! any idea how much heat should i use on the pcb as i am going to use the hot air soldering method with a 5mm wide blower tip for these tiny components and i do not want to burn the pcb or ruin anything....cheers mate

    Christian

  7. #7
    motorolanovice No Longer Registered

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    Quote Originally Posted by throwed View Post
    ythanks for the reply mars , i appreciate it greatly! any idea how much heat should i use on the pcb as i am going to use the hot air soldering method with a 5mm wide blower tip for these tiny components and i do not want to burn the pcb or ruin anything....cheers mate

    Christian
    Seriously I hope this isn't a customer radio. Radio tech like myself have had extensive training in removing components without damaging the board. You need special tape to cover near by components from heat and its something that needs to be done correctly. Maybe you should contact a professional before you fry your toy.

  8. #8
    throwed No Longer Registered

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    motorolanovice .. where are you located ?

  9. #9
    motorolanovice No Longer Registered

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    Quote Originally Posted by throwed View Post
    motorolanovice .. where are you located ?
    I only do work for major company's and my own hobby stuff. I you want quality work I recommend http://www.cabearcom.com.au/

    there head office is in parramatta in NSW but they can help you anywhere in aus.

    They will perform your mod, update the firmware and align your radio for a good price, speak to a salesman named bobby.

  10. #10
    syntrx No Longer Registered

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    They know this makes the radio illegal to operate both on the LMR bands as well as UHF CB (where it wasn't legal anyway), right?

    Doing a mod like this to your own radio and keeping quiet about it is one thing. A business doing this commercially for customers is another thing entirely; they must be looking for smack down from ACMA. They are actively chasing people for using LMR gear on UHF CB at the moment.
    Last edited by syntrx; Apr 25, 2013 at 01:36 AM.

  11. #11
    motorolanovice No Longer Registered

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    Just because he wants to mod it does not make it Illegal. How do we know what's he's going to do with it, for all I know its going to be set at 1watt and used as a room to room communication device.

  12. #12
    mikem No Longer Registered

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    If you are determined to use a hot air gun and cutting wheel but you don't know the correct temp profile then like others have said you need to protect adjacent components near the resonator that you are so hell bent on destroying. I would use some kapton tape over all adjacent components to protect them from excessive heat but even this route of heating and/or cutting away at the ceramic resonator with a cutting wheel will possibly damage the VCO. The proper way is to identify one by one all components in the existing VCO and draw up a schematic and then analyze it with any free modelling program then choose the best components to change to move the VCO to the new range. Use a sensible method instead of blindly cutting and grinding, this is similar to what the excellent software engineers on this group use to dissassemble software for all of the modifications listed in the various sub directories.

    If you don't agree that doing your modification correctly and you are in a hurry to mess your radios hardware up then I'd suggest buying the correct split radio.

  13. #13
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    I do a lot SMT work for prototypes, etc. For resistors and capacitors I just use two temp controlled Weller irons with appropriate tips, one for each side of the component. Holding an iron in each hand you can easily grip and lift the part off the board without damage.
    It is a fine thing to be honest, but it is also very important to be right

  14. #14
    coreyapollard No Longer Registered

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    Hi there Motorolanovice,
    regarding Bobby at cabearcom, it appears that Bobby no longer works there and others I spoke to there didn't seem confident in reply about this mod?
    any other recommendations?

    cheers

  15. #15
    harrold No Longer Registered

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    Quote Originally Posted by coreyapollard View Post
    Hi there Motorolanovice,
    regarding Bobby at cabearcom, it appears that Bobby no longer works there and others I spoke to there didn't seem confident in reply about this mod?
    any other recommendations?

    cheers

    I wonder why he does not work there anymore after his name being posted on here.


    In Australia this is a pretty common mod to wish for. All the XTS5000's do the split, but the mobiles don't seem to be very happy at going higher than about 475.

    The splitsa with have a choice of are 380 - 470 and 450- 520. If you want 70cm and CB you really are in a bit of trouble.

    I am not sure how far the 450 - 520 split goes down.

    I have played around with this on 380 - 470 radios and have noticed they do not mind RX up into 500Mhz.

    If someone can work out this problem for people in Aus I think there will be many happy punters.

    Cheers

    Harry

  16. #16
    freerider-aust No Longer Registered

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    Looking at the DSM it appears the xtl does not work the same as the astro spectra the vco and pll set up is different.there is various ways the vco freq could be raised c5835 could be changed from 5.1 pf to 4.7 pf.another mod i have done to other radios is to remove small amount of plating from the resonator (u5826 on xtl radio) this could be done by carefully scraping plating off or using solder and soldering iron this removes plating easily.my radio goes to 475 so it only needs to go 3 megs. if your going to try any of these the resonator mod is not reversible with out replacement
    disclaimer do at your own risk i have not tried this on xtl yet

  17. #17
    freerider-aust No Longer Registered

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    Can any one tell me if the high range tx vco is under a shield and if so is it easy to remove
    or does the chassis make up part of the shield
    i have not dissemble the radio yet
    thanks david

  18. #18
    freerider-aust No Longer Registered

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    Quote Originally Posted by freerider-aust View Post
    Looking at the DSM it appears the xtl does not work the same as the astro spectra the vco and pll set up is different.there is various ways the vco freq could be raised c5835 could be changed from 5.1 pf to 4.7 pf.another mod i have done to other radios is to remove small amount of plating from the resonator (u5826 on xtl radio) this could be done by carefully scraping plating off or using solder and soldering iron this removes plating easily.my radio goes to 475 so it only needs to go 3 megs. if your going to try any of these the resonator mod is not reversible with out replacement
    disclaimer do at your own risk i have not tried this on xtl yet
    i have done one of the mods with success i removed a small amount of plating and it worked i had to do it a bit at a time approx 2mm from the top nearest the centre pin that attaches to the pcb.i scratched it with a stanley knife but that is very slow i then used a very small fine file
    the radio goes to 477.400 i have not tested any further
    the amount you need to take off will vary depending how far the radio goes unmodded the one i done went to 475mhz
    again do the mod at your own risk take time and be carfull
    david

  19. #19
    freerider-aust No Longer Registered

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    Quote Originally Posted by freerider-aust View Post
    i have done one of the mods with success i removed a small amount of plating and it worked i had to do it a bit at a time approx 2mm from the top nearest the centre pin that attaches to the pcb.i scratched it with a stanley knife but that is very slow i then used a very small fine file
    the radio goes to 477.400 i have not tested any further
    the amount you need to take off will vary depending how far the radio goes unmodded the one i done went to 475mhz
    again do the mod at your own risk take time and be carfull
    david
    have done a second radio with no problem. the resonator mod is far easier than doing micro surgery changing resistors and capacitors
    david

  20. #20
    freerider-aust No Longer Registered

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    RES.jpg
    Heres a picture of the modded resonator the longer one is the one with the mod compare it with the shorter one and you will see how much i removed. that radio already went to 476 my other radio required about another 2 mm more
    hope this help any one doing mod.be very careful when fileing it.its a expensive radio to screw up
    david

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  22. #21
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    I am not seeing where the mod was done was it shortening the silver "tongue" sticking out from the center of the resonator body? Or is is scraping the plating off the body at that end? An arrow or circle might be helpful, or a little more describing the mod, thanks!

  23. #22
    freerider-aust No Longer Registered

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    RES.jpg
    i have circled the part of the resonator that needs to be filed. look at the other resonator its unmodded you should see the difference.the amount that needs to be removed will vary with each radio
    hope this helps

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    Man that circle is still really hard to see, but I finally found it, you sc-rap-ed off the outer plating of the resonator at the end, it looks like. OK, thanks for the clarification!

    REALLY? The stupid board is censoring sc-rap-ed for the word "r-a-p-e-d". OH come on, this is getting ridiculous.

  25. #24
    freerider-aust No Longer Registered

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    you can scra-pe or file it appears to be ceramic and is really hard and the plating is very well done.i used a file
    i only needed a few mhz so i dont know how far you could go

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    make lots of short cuts and measure that way to dont llose the bottom end by mistake