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Rm Italy KL-503 watts vs amps

Discussion in 'General CB Services Discussion' started by CbRadiosPRONTO, Jul 19, 2014.

  1. CbRadiosPRONTO

    CbRadiosPRONTO Performance Ready Radios

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    Looking at this amp, it appears the max output SSB is 450w but the max amp draw is only 30 amps. That seems awfully low. Is the 30 amp max draw incorrect?

    The other thing that seems low is the input power rating of 12 watts. Is that the max you can drive into this amp?


    CbRadiosPRONTO


     

  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Typical RM rating IOW bullshit rating. They typically rate something at nearly twice what it will put out. The big clue is the fuse rating. Mulitply the fuse rating by 13.8 volts and then divide that result by two and you will be close to the actual power output. That amp draws 30 amps so 30 x 13.8= 414 watts 414/2 = 207 watts which is more inline with reality. A typical 100 watt ham transceiver requires about 20 amps of current. Some need 25 amps. Getting 450 watts with just 30 amps draw absolutely defies the laws of physics since it would require the amp to be MORE than 100% efficient. RM is one of the worst for overstating ratings however most CB amp manufacturers do the same thing.
     
  3. Lil'Yeshua

    Lil'Yeshua .......

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    My KL203 has an internal 12 amp glass fuse. I'm guessing that it's overrated as to keep from popping fuses all the time. The same could for yours. Of course I keep my 959(no swing mod) on the am side turned down to 1-1 1/2 watts and SSB at 12 watts pep.
     
    #3 Lil'Yeshua, Jul 19, 2014
    Last edited: Jul 19, 2014
    AL567 likes this.
  4. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    I repair KL amplifiers and the number one cause of failure is the amps are over driven. The second is over voltage. These are inexpensive amps and usually work well. The promise of 500 Watts from the KL503 is very optimistic.
     
    Shadetree Mechanic and 222DBFL like this.
  5. CbRadiosPRONTO

    CbRadiosPRONTO Performance Ready Radios

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    Ok. Thanks for the feedback. What transistors are inside the kl503?


    CbRadiosPRONTO
     
    #5 CbRadiosPRONTO, Jul 19, 2014
    Last edited: Jul 19, 2014
  6. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    The 503 uses erf7030 fet's and the other uses the no longer in production MS1051. Rm Italy has re-biased the unit that uses MS1051 transistor to run the MRF 454.
    The re-bias is necessary, RM Italy says it is not a direct drop in replacement. If the bias is left as is they warn of possible further damage to the circuits.
    The kl-505 is more of a ham amplifier because of the frequency range 3MHz to 30 MHz.
     
  7. JoeDirt

    JoeDirt Well-Known Member

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    IRF520/ERF2030's are the replacements for the KL503 NOT ERF7030's !

    My KL503 only produces 150 linear watts anything more saturation is noticeable.

    For SSB operation i also had to increase C34 by 12pf to provide enough bias to TR2. If you have choppy audio with your KL503 then this mod should fix that.
     
    Robb and Klondike Mike like this.
  8. Lil'Yeshua

    Lil'Yeshua .......

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  9. magnuman

    magnuman Active Member

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    the kl503 doesnt put out 450w regardless of what is written.
    i have one. 275w is max. and it doesn't sound very good so I never use it. might try the mod suggested above. for RM amps use the rating given as "input" watts and multiply the value by 60% to get the real figure.
    KL503 has 9 irf520 type mosfet transistors in a 1 driving 8 configuration. You are limited by the single driver as to what you can put into it.
    the amps only redeeming feature is that it is cheap.
    there is always a good reason why something is cheap.
    Skip over the 503 and get the 505v, which is quite a nice amp.
     
  10. Lil'Yeshua

    Lil'Yeshua .......

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  11. CbRadiosPRONTO

    CbRadiosPRONTO Performance Ready Radios

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    1 irf520 driving 8??? Seriously? Seems pretty stupid. May as well just be a straight 8. It would be much more versatile. Though, I suppose it would be hard to blow the final stage in that unit. I suspect the driver gets pretty stinking hot though.



    CbRadiosPRONTO
     
  12. CbRadiosPRONTO

    CbRadiosPRONTO Performance Ready Radios

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    What's in the 505v?


    CbRadiosPRONTO
     
  13. vkrules

    vkrules Sr. Member

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    4 x mrf 455 wish it was the mrf454.
     
  14. vkrules

    vkrules Sr. Member

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    The 505 is a nice little amp but don't expect the wattage some are claiming As said earlier Rm rate their amps in Final input power.Be interesting to see what they have changed in the 505 to get it approved as the 7505( or will we be paying more for the sticker)
     
  15. Lil'Yeshua

    Lil'Yeshua .......

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    Frequency 3-30 Mhz, HF amplifier, with 2 cooling fans,
    Mode AM-FM-SSB-CW (This amp does not work well with Flex or KX3)
    Input power: 1-15 W AM/FM, Input power: 2-30 W SSB/CW , Output power - 300 W Max AM/FM, •Output power: 600 W Max SSB/CW
    Supply 12-14 Vcc, Output power level - 6, Antenna preamplifier - 26 dB
    Made in Italy, This model is for export only, only ship to the address outside of US
     

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