(I think he really likes the color blue) (-: Same maker takes pride in all his boxes over the years, I never saw one of his that wasn't AB, he also made the Blue face Palomar 225's 250's 350's (Also with the Galaxy name on them, also blue) as well as the Palomar/Magnum name on them as well as the Skipper/Palomar name on them and the Cobra XL name. I had two versions with the MRF 454s' and two with the 2290s.although the 454's did slightly more for some reason or other.Īlways pretty much the same, 2 to 20 on AM would give me a little over 100 watt DK with slightly over 400 pep and about the same on SSB with the 454's and slightly less with the 2290s. I've been through 4 of these amps over the last 5 years or so, along with being good AB amps. How much carrier and power are you feeding the amplifier with? These amplifiers have a decent class AB bias circuit and do not need a lot of drive. Depending on what you use the amplifier for I would just do as described above or add a variable power to it using a 2 watt 100 ohm potentiometer and some 2 watt 100 ohm resistors.

Nope, when I repair these I have to use ohm meter to 'ring' out what does what. Lower value resistors like a 50 ohm will give you more attenuation on the input. Or do like someone else mentioned and feed it directly to where the green cap (I think it is marked 68) and then solder a 100 ohm 2 watt resistor from the point where the green cap is to ground. This will give you variable input power instead a 4 position switch. You may have to swap the outer leads around to your liking as far as which way is up and which way is down. The other out leg would go to ground through a 100 ohm 2 watt resistor.

One outer leg of the pot would then connect to the input of the amplifier where green cap is (dark brown rosin spot on the board) through a 5 or 10 ohm 2 watt resistor.

To add the variable power pot you would need to feed the center leg of the pot with center conductor of the small coax you pictured that used to go to the rotary switch. Click to expand.Nope, when I repair these I have to use ohm meter to 'ring' out what does what.

Cobra xl 450 linear amplifier