issue with amplifier in the car

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Ur5by9
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issue with amplifier in the car

Post by Ur5by9 »

Good evening Gents,

I have been out mobile a bit and recent purchased in inexpensive amp for the car.
I Seem to have a slight problem which I am unable to identify as a fault.

Tested using 2 different radios.

A 40 channel cybernet radio and a president Lincoln mk1

president to KL200 amp SWR bridge and Sirio mounted antenna works fine, from 500mw to 10Watts variable no issues.
cybernet radio regardless of HI /Low power the KL200 amp makes a fast clicking sound and the output is less that the inputted power.

Nothing changes besides the radio and the power leads are different however into the same socket in the car.
I use 213 patch leads and both power cables have a ferrite ring to eliminate RF feeding back down the power lines.

I cannot think to find the issue?

Whats your thoughts on this problem?

:wave:
speeddemon

Re: issue with amplifier in the car

Post by speeddemon »

Hi ur5by9 is it hooked up correctly? Radio output to amp input/ ant to amp output.? If you hooked it right then I thinks you have a bad rf txt relay circut in amp or bad transistors in amp or both max input to amp is 5 watts you can damage the little amp by overdriving it . Gd luck n cheers n 73's
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Ur5by9
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Re: issue with amplifier in the car

Post by Ur5by9 »

Hi there and thanks for the reply, Yes its set up correct and as I said, switching between the two radios the President works absolutely fine
Its only when I change to the cybernet radio it fails to work correct, I have even tried this with the 2 radios side by side only removing
the PL259 from one radio to the next.

Very odd problem which is a bit strange to say the least.
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Phuture
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Re: issue with amplifier in the car

Post by Phuture »

Are you able to check the RF power coming out the back of the Cybernet radio when it's connected? If not, what does the RF power meter on the radio show you when you key up with and without the KL200 inline?
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Ur5by9
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Re: issue with amplifier in the car

Post by Ur5by9 »

The Rotel is doing 5w out on Hi and .5 on low with the amp inline the relay just clicks very fast.
President on half a watt drives the amp fine.

Cant honestly figure this one out....
speeddemon

Re: issue with amplifier in the car

Post by speeddemon »

Hi cooper has anyone moded the amp to take a lower drive input ? Is there any extra resistor in side on the input of the transistors .? or did someone monkeyed around and changed the values of the resistors inside of it . Cheers n 73's
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Phuture
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Re: issue with amplifier in the car

Post by Phuture »

Might be worth putting your SWR/Power meter between the Rotel and the KL200 to see if anything can be detected there and comparing the results to what you see between the Lincoln and the KL200. Additionally, if you replace the antenna with a dummy load of adequate capacity does that change anything?
The Collector
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Re: issue with amplifier in the car

Post by The Collector »

Would a higher SWR on the Cybernet make a difference in the reflected power going back through the amp and the relay cutting out??? Perhaps double-check the SWR's on both.

P.S. I know next to bugger all about amps etc so may be talking out of my bottom ;)


Maybe the amp is racist :)
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ROTEL240
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Re: issue with amplifier in the car

Post by ROTEL240 »

How long is your patch lead ?
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cb4ever104
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Re: issue with amplifier in the car

Post by cb4ever104 »

Try another patch lead regardless .
30TM060
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Ur5by9
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Re: issue with amplifier in the car

Post by Ur5by9 »

Done some testing and now have a new problem.
President - amp - antenna fine
Rotel - amp - antenna - amp clicks fast nothing has changed besides the radio

Antenna is SWR 1.1 - switched out the antenna for a dummy load same results
found an old midland in a box connected this up and it worked fine.

The issue seems to be only when the rotel is being used.
Now another twist I have another rotel brand new in a box ( rvc 230 ) which I reluctantly took out and connected that up
only to have the same results as the other rotel.

I switched out patch leads same results.

Now I have a new problem the amp is dead - fuse is fine no shorts but the Large resistor is quite scorched looking.
It went while testing the rotel.

Resistor : brown - white - orange - silver, its quite burned 19k Ohms 10%
Not sure If I can find a schematic for the KL200-P to double check the correct value and wattage.

So ....a bit lost besides this new set back.
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Re: issue with amplifier in the car

Post by wa10 »

There should be 2 large resistors in a kl200, its the input attenuator, neither are 19k so im not sure what you are looking at,
10w fm input will fry them,

have you made sure the amp has a negative connection & not getting its ground through the rig via the patch lead,
i have seen that issue burn out power line chokes in radios that have them but seem to work ok with rigs that don't have chokes.
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
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Ur5by9
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Re: issue with amplifier in the car

Post by Ur5by9 »

That's a good question to be fair I have not checked the ground, although it works fine with a president and a midland but not my Rotel which was the intended radio for the car.
The resistor is very discolored so I may be very wrong with the values,
It is the one right off the OP transistor that is burned out, I don't know the previous history with this amp to be fair.
What is the correct value or replacement you recommend.

Since is now seems to be dead any other known components to check. It just stopped while testing with a Rotel and no longer lights up.
I have stripped it out the case for testing.
Fuse and diode are fine.
wa10
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Re: issue with amplifier in the car

Post by wa10 »

have a look at the service manual board layout to identify what's been cooking,
http://www.cbradio.nl/rm/kl200.htm

simple test, does the amp still light up when the patch lead is disconnected,
is it dead when you put the other rigs back inline.
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
wa10
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Re: issue with amplifier in the car

Post by wa10 »

The Collector wrote: Would a higher SWR on the Cybernet make a difference in the reflected power going back through the amp and the relay cutting out??? Perhaps double-check the SWR's on both
The antennas match to the coax is what determines vswr,

a rig or amplifier does not effect vswr unless its oscillating & spewing rf on frequencies where the antenna does not match the coax impedance,
or you have cmc on the coax braid & putting the amp & patch lead inline alters the common mode impedance of the braid seen in parallel with the antennas impedance,

changing power output can give an illusion that vswr rises with increased power even after you recallibrate the meter,
that's the meters detector diode none linearity creating an illusion & not vswr rising.
The Collector wrote: P.S. I know next to bugger all about amps etc so may be talking out of my bottom ;)
You know something about amps now ;)
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
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