Palomar Star IV amp schematic needed

[8113 Northern MN]

Today i spent several hours talking with Europe...abusing my new beam..and seemed to have put my linear above what it wanted to do. I heated it up a bit too much and smelled some smoke. There is what looks like a resistor that goes from the medium portion of the 3 position switch to the circuit board. it has completely fried. I am unable to read it or tell what the bands were on it. Wondering if anyone has a schematic for this amp so that i can repair it properly.

 

[Tallman]

If you could take a picture of the switch area I might be able to figure out what value they are. Usually they are between 20 to 40 ohms. It just drops more of your signal to lessen the drive.

 

[8113 Northern MN]

this is the resistor(?) in question. If you notice by the picture it is bulged in the middle. the bottom side is burnt through and these are the only remaining numbers left on it.

This is the whole switch...resistor on the right side colored brown red brown is the low setting....the ferrite core wrapped in white and black is the middle high position and the burnt up resistor(?) is the medium position

 

[AudioShockwav]

The ferrite is the input combiner, most of these use 120 or 150 ohms on one side and 27 ohms on the other.
Is the amp still making power on the other settings?
If you are overheating the input swamping network you are driving the amp too hard, reduce the input.

73
Jeff

 

[8113 Northern MN]

the amp is still working perfectly on all three settings actually....just all three are the same output...ive reduced the input quite a bit..but still heating up after long qso's

 

[AudioShockwav]

That little fan in the back is not much help getting rid of internal heat.

I would set it up to run on high and dial the power back on the radio to get about 80 or 90 watt dead key on am and look for 300 watts out on peak on SSB.
The low and med settings are just bleeding input off to ground anyway.
What are you driving it with?

One heat sink is for the pass transistors of the power supply and the other side is for the amp, both can use additional cooling.

73
Jeff

 

[8113 Northern MN]

I have a Kenwood Ts-130s tuned down and only putting out 35 watts into the Amp. Ive read that a high drive linear is safe to put this 35 into.

 

[Tallman]

The resistor in question is a 39 ohm 5% tolerance. 35 watts is too much input. I can't be certain but I think 20 watts is maximum for that amp.

 

[ExitThirteen]

20W PEP input max on that Palomar amp, no more. Tallman is correct on the resistor value. 39 ohms @ 2W.

~Cheers~

 

[AudioShockwav]

http://www.cbtricks.com/Amp/palomar_other/elite/palomar_elite500.pdf

Same basic amp, sold under many names using MRF 455 in the older ones and 1446`s in the newer ones.
I also agree, 20 watts max peak input power, I would still limit the carrier to 80 or 90 watts OUT of the amp on AM/FM and no more than 300 on SSB.
Remember that the 1446/455 transistors are 60/70 watt devices.
Any of the superstar/boomer/palomar/green lizard/red devil/commander/blue thunder/elite/shooting star and all the rest of the clone amps , regardless if they say HD or not are low drive amps.
Even the Texas star HD and HDV amps should be limited to no more than 20 watts peak input.
There are a very few exceptions to this rule.
Most of these are built off old motorola designs that were never meant for more than 2 or 3 watts carrier and 12 to 15 watts SSB input.

73
Jeff