Cobra 2000 Doesn't Like My Amp

[Uneasy Rider]

I just picked up a nice talking Cobra 2000. I have been using an older Cobra 139XLR and my trusty RCI 2980 with a Boomer/Palomar type 600 5 pill amp. My tech was able to match the 139XLR to the amp and it was getting about 500 watts on SSB. Amp worked fine with the 2980 as well. I put the Cobra 2000 inline and set the added variable control down to a 1-watt dead key. I run this amp on low because that is about all my Pyramid PS- 36KX can handle. When I keyed the mic, the amp stayed keyed, the Pyramid protection light went on and it squealed, the SWR's may have jumped and it sounded like distortion coming from the 2000's external speaker. I immediately shut down the amp. I bumped up the dead key to 4 wats and with my finger on the amp's off button, the same thing.
I hooked up the RCI 2980 back up to the amp and it worked fine. I put the 2000 back inline and swapped out the amp with a Texas Star DX 350 and it worked fine with a 1- watt dead key. I am getting about 150 watts out of the DX-350. Radio alone is putting out about 10 watts peak.
I was going to take the 2000 and the 600 amp to my tech and see what he tells me. I'm just curious if anyone knows what is happening. Is there simple fix before I go and spend more money and possibly have to wait to get my gear back? I don't understand why the amp doesn't play well with the 2000.
I know I could use a power supply with more amperage but the 600 amp on the low setting has been working fine with my other radios. Normally when I overload the power supply, the power supply just squeals and the protection light come on.
Any help is always appreciated,
Uneasy

 

[nomadradio]

There's a real coin toss for you. Is the radio unstable with only this amplifier?

Or is this amplifier only unstable with that radio?

We have seen coax jumpers with a marginal ground inside the plug cause this sort of wackiness. The connection checks okay from one end of the jumper to the other with just a continuity test. But flexing it with the radio on a dummy load allows receive noise to "leak" into the radio's receiver. Turning off the ANL can make this easier to hear. But only when there's a significant noise level to start with. A coax jumper that reveals ANY change in receiver noise when flexed and connected to a dummy load has a problem.

Still sounds like a coin toss to me.

73

 

[9C1Driver]

I really think you need a bigger power supply as well.

 

[Uneasy Rider]

There's a real coin toss for you. Is the radio unstable with only this amplifier?

Or is this amplifier only unstable with that radio?

We have seen coax jumpers with a marginal ground inside the plug cause this sort of wackiness. The connection checks okay from one end of the jumper to the other with just a continuity test. But flexing it with the radio on a dummy load allows receive noise to "leak" into the radio's receiver. Turning off the ANL can make this easier to hear. But only when there's a significant noise level to start with. A coax jumper that reveals ANY change in receiver noise when flexed and connected to a dummy load has a problem.

Still sounds like a coin toss to me.

73

Nomad you got me on the right path. I put a new radio in and I assume it had something to do with the last thing I did. Well it sort of was. I moved some cables around.
Having experience in sound reinforcement I should have thought about cables. I took the jumper out going to my meters and ran antenna coax to the back of the amp. Guess what? I can run the amp on high now. My jumpers are old RG213U that are kind of stiff and they have been manipulated in many directions.
Thanks again!

 

[Uneasy Rider]

I really think you need a bigger power supply as well.

I think you are right. Even though I can now run the amp on high, I could always use more headroom on the power supply.