Cobra XL-450 Amplifier

[FredTx63]

For sale: Cobra XL-450 Amplifier in pretty excellent condition.

The only real flaw is fixable. For whatever reason, the previous owner decided the engraved labels for the two SO-239 connectors weren't good enough and had to write their labels with a sharpie on the back of the amplifier. This would probably clean of pretty easily. Other than that, it's in excellent condition and does what it's supposed to.

I've included a picture of the inside, looks all original to me. Too bad the ground strap common to the 4 transistor models of these amplifiers cover the markings on the transistors - look like Toshiba markings to me? Could be 2290s.

Either way, these are desirable for their effective AB biasing & filtering circuits making them ideal for producing clean output on SSB.

$300 shipped CONUS prefer PayPal for payment. PM me if you want it.

 

[Sommerkamp]

Hi, i am interested in it do you have a phone number so i can call you.Thanks

 

[FredTx63]

Sent you a PM.

 

[NZ8N]

M.E.K. will take all or most of the Sharpie markings off. Sometimes Acetone will, too.

 

[Big Kahuna]

Interested as well Fred if Sommerkamp doesn't take it.

 

[Cabover Bob]

Brake clean takes sharpie off......

 

[techradioman]

That one resistor located on the power selector switch is either open(bad) or had severe heating.

 

[Robb]

The square blue trimmer pots near the front looks like adjustments for biasing. Not familiar with that amp. But if OEM or not, still a good thing just the same . . .

 

[Sommerkamp]

Hi, i try call you but your mail is full do you have another phone number i can call you.

 

[FredTx63]

Sommerkamp, never saw a missed call? I'm taking the amp to my tech this weekend to have him check out the discolored resistor pointed out above. Once that is replaced (if necessary) and given a 100% clean bill of health I'll PM you - shouldn't take but the weekend.

 

[ButtFuzz]

That baked resistor is a casualty of over-drive...
Why do they put those silly power level switches in there, anyway?
I am no expert, but the first thing I do when I am re-furb'ing an inexpensive leenyer is pull that prone-to fail / prone to cook mess out of there and bypass it with an adequate wire.

AND STOP OVER-DRIVING THE AMP.

Drop the input wattage down lower and let the amp amplify, rather than increasing the input wattage and dropping the input / output with a resistor.

 

[Handy Andy]

The Amp is not made for "10 ohm smoke" it uses 18 ohm - so the Transistor it's paired with, pushes the Base a little higher up from Class C.

This amp was designed to run low, not as a poor performer, but done up for long-term survival in conditions that may be less than ideal.

It can explain the reason for the discoloration of the power resistor - chatty people, SSB for Skip - having to repeat the directions to the Doughnut shop - repeatedly - for those needing a sugar rush washed down with caffeine - wear and tear - but @ButtFuzz mentioning the requirement and the proper means to drive it - certainly applies to and for anyone.



Sure, it may not be stellar power performer - the design puts this into a category by itself - sure - it's gonna' have a little more heat, a little less power, but it has a cleaner output - doesn't make it better dollar per watt wise, it makes it cleaner and better in the Cost of that Watt in the usability and lifetime use in-between Mean Time Between Failures (MTBF).

If it works, don't fix it.

 

[Sommerkamp]

Hi, did you get the amp check out you said you would you send me a message

 

[Sommerkamp]

Hi, do you still have the Cobra Amp let me know.Thanks

 

[Sommerkamp]

Hi, let me know if you change your mind if you want to sell it.Thanks