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RM KL203-P

Discussion in 'Amplifiers' started by Dr DX, Feb 1, 2018.

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KL203-P high low mods

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  1. Dr DX

    Dr DX Member

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    RM_Italy_KL203P%20(1).jpg Can any one be of help I am trying to find information on the RM KL203-p Linear I would like to install a mini toggle switch in it being the amp is so small I would like to be able to switch it to either low or high output power would any one have any drawings or schematics with this modification with the parts list. Please any help would be deeply appreciated


     

  2. BammBamm

    BammBamm Chicago's mudduck.....173 on the southside.

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    I own one and could get you an inside pic but why do you want a high / low switch? With a 1 1/2 watt dead key swinging to 8 watts on AM I seen about 85 watts and SSB at a peak of 12 watts showed about 135 watts. If you have a variable output radio set low power at 1 1/2 watts dead key and use that for amp input..if you want "low power" turn off the amp and turn up the variable power..let' say you did install this switch..nobody would know or hear the difference..most people that heard my 980SSB with my 203p connected to it thought it was a just a converted and peaked 10 meter radio..I was never accused of using an amp. Don't get me wrong it has been a good amp but your not going to "drop the maul" on anyone. Make sure your SWR is good and use a low deadkey..1 - 2 watts and it will last and sound good.
     
  3. tba02

    tba02 WOOF

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  4. 9C1Driver

    9C1Driver Sr. Member

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    Not much to vote on about this really. The KL203-P has been around for years, it's a cheap low dollar throw away amp that does ok for the money. BammBamm pretty much said it all, a hi lo on this small of an amp would be pointless. Another popular choice in this range would be the KL-203.
     
  5. 9C1Driver

    9C1Driver Sr. Member

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  6. tba02

    tba02 WOOF

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    I have never heard of a KL-203P with a bipolar junction transistor.
     
  7. Low_Boy

    Low_Boy Well-Known Member

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    The KL203P has pre amp. KL203 has no pre amp.
     
    BammBamm likes this.
  8. 9C1Driver

    9C1Driver Sr. Member

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    It might have been called the KL200-P, can't remember now that I think more about it. Maybe the difference between the 203 and 203P is a pre-amp. Either way the 203 is a decent little amp for the money, just don't overdrive it and he should probably add a small fan.
     
  9. BammBamm

    BammBamm Chicago's mudduck.....173 on the southside.

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    The 203p does have a pre amp and it does seem to work well..I used this amp for about 3 months mobile and now use it on a power supply on my base.
     
    9C1Driver likes this.
  10. psycho

    psycho Running a special on our rooms!

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    Running a KL amp is like having sex with an extremely mouthy, ugly woman.........you might get what you want but you never want anyone else to know you had one. I still find it hard to believe that these POS amps are relevant in any way.
     
    Tallman likes this.
  11. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    That's time for ear plugs and two paper bags!

    The 200 is a class "C" amp and not worth the gas to burn it.
    The "P" in the part number indicates a receive amplifier boost. It is a junk circuit that amplifies everything coming in to the antenna. A lot of times the signal you want is lost in the increased noise.
    It is not a tuned circuit and not selective.

    The best mod for the KL-203 and the KL203P is to modify it for a higher dead key drive.
     
    #11 Tallman, Feb 22, 2018
    Last edited: Feb 22, 2018
  12. BammBamm

    BammBamm Chicago's mudduck.....173 on the southside.

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    It amazes me how many will bash this amp or any product that they deem to. If you read the reviews on this amp about 90% of them are positive...yes it's a LOW drive amp, yes the pre amp amplifies EVERYTHING and yes I honestly have and use one! Am I embarrassed to admit it? Not at all, as a matter of fact I have recommended this little disposable amp to many..why you ask? Because it's a cheap way to get 100 watts and living in the Chicago area theft is common plus if it burns up your out like $50! I keep hearing people that have never used one say how terrible they sound yet I have had nothing but positive comments. I drive mine with 1.5 watts AM and about 8 watts on SSB and I see 80 ish watts AM and around 115-120 On SSB..I'm not saying this is the best amp ever but how are you going to comment on something that you have never used? I know...unless it's FCC approved ham gear it's not good enough for some...
     
  13. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    My comments are based on repair experience because I repaired the RmItaly product line for two distributors. One of which is the sole distributor for the US and any that got repaired or replaced was evaluated by me or one of my technicians. The other distributor has the South American market.
    So I did see a lot of the 203 amps and everything else they manufactured on a daily basis. The 203 is perfect for users like you that don't want to draw too much attention to yourself. They actually are surprisingly clean as long as the signal is going in is clean and has not had the "SUPER WHACK PACK HACK" done to them.
    As the saying goes "Garbage In=Louder Garbage Out!"
    works on any amplifier. There is no filtering in or out of the amp.

    They are the true throw away amp, and they are a bargain for the price and a good investment if you know how to replace the fets.
    The bench fee we charged was $35.00 for hook up and evaluation, plus parts for repair quickly exceeded the cost of a new amp. I seriously advise to only buy the straight 203 and not the 203P. If the "P" section fails you lose your amp unless you know how to fix and have parts readily available.
    The $35.00 fee was set by the distributors not by me. They did not allow free estimates, because they wanted to sell more amps.

    And finally do I use amps, no. Never on CB, and so far not on Ham bands, not yet. Do I have amps available, Yes more tha you can imagine.
    If you need a power transformer for a KLV-1000 I have them.
     
  14. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    The KL-200 is a class "C" single bipolar and really sound like crap on SSB.
     
  15. nomadradio

    nomadradio Analog Retentive

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    Hey, Dr DX.....

    If you haven't already bailed on this thread, here's my take on your question. I have done this on a lot of amplifiers, especially solid-state mobile amplifiers from the 70s and 80s. Mostly, we would leave out the "high" switch since we were simply making the amplifier compatible with a radio that's just too big for it.

    To do what you ask requires breaking the connection between the antenna relay, and the amplifier circuit. This is the circuit path feeding your radio drive into the amplifier circuit.

    This will require finding the correct foil trace on the circuit board that carries this circuit and cutting a gap in the foil. The simplest of all methods is to wire a resistor across the cut in this foil trace. The resistor will now turn some of the radio's drive power into heat, and the remaining wattage will be what drives the amplifier.

    Two problems with this approach.

    First one is that you can't accurately calculate the resistance value of this resistor in advance. To get the desired drop in power will require what's commonly called a "cut and try" method. I would start with a 22 ohm resistor and see how much the power is reduced. If it's not enough, a higher value gets tried. And if it gets cut down too much, a lower value.

    Now for the other problem. The amplifier must fool the radio into operating as if it were connected to an antenna. The amplifier's input circuit should have an impedance that is nearly the same 50 ohms as a properly-adjusted antenna. You check for this by putting a SWR meter and an additional coax jumper BETWEEN the radio and the amplifier. You key the radio with the amplifier set to operate, and measure the SWR as if it were an antenna. If the amplifier's input circuit is well designed, you'll see a reading under two to one. And if it's a sloppy design, this reading will be higher.

    The "one resistor" method of reducing the amplifier's drive will change this "input-side SWR" reading. If it pushes the SWR too high, you need a more-complicated type of solution called an attenuator. The one we use in the Pride DX300 amplifier to cut the drive level in half uses three resistors. If you have a high input-side SWR with the single-resistor solution, you will need at least one other resistor that connects to ground to remedy this issue.

    The wattage rating on your single resistor, or on the three we use in the Pride must be large enough to absorb the radio drive power without overheating.

    If I were to try this, I would probably just use the "Preamp" switch on the front of the amplifier, taking it loose from the preamp function and rewiring it to simply short across the single-resistor setup. That would restore your normal (original) drive level. There is no good place to drill a hole and mount an additional switch on this amplifier.

    But this would be a design project. Nobody has done this modification and posted it for us to copy that I know of.

    73
     
    Shadetree Mechanic likes this.

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