Cobra 25 not putting out audio

[74fordman]

Hi all new here. I have a cobra 25 ltd classic that doesn't seem to be putting out any audio. If you key the mic it dead keys at about 2.5 watts but no swing when talking. Playing with it today I couldn't get anyone to answer me and if I plug the external speaker into the pa side I just get static no audio. Thought it was the mic put on a new one still no good. I can receive all day long loud and clear just not putting out. Anyone have any ideas where to look? Oh and I've owned it since new all stock was working a couple months ago pulled it out today and no good.

 

[Handy Andy]

Cobra 25 LTD Classic...hmmm...

Offers ON/OFF-Volume, SQ, RF Gain and Dynamike - I'm thinking there may be a broken circuit in the Pin 2 Audio line.

Quick check? Requires a DVM or Ohmmeter - don't need the power connected - prefer it's not.

Ok, so you can get underway...

Here's a photo of a typical COBRA 4-pin mike
- the PLUG end, of the one you hold in your hand
- note the Pin 1 and 2.
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In the front panel - they meet up, but are mirrored (the Opposite reference) - so locate the notch, Pin 1 and Pin 2 - on the plug, and locate those same two pins on the JACK - the Radio end...

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Remove the mike, At those pins of the jack, locate Pin 1 and Pin 2 - test RESISTANCE at 2K setting

ACROSS Pin 1 to Pin 2 - and rotate the Dynamike control - that reading on your test meter should vary as you rotate that control

With the Dynamike control to the Far Right, (all the way up) the resistance should be about 900 ~1.1K ohms

All the way down, control to the far LEFT, the DVM should show about 10 to 30 ohms.

If you get those readings - then the Mic jack isn't the problem - nor is the Dynamike control.

I'll wait here to let you catch up...

 

[74fordman]

Ok ill check that tomorrow and get back to you

 

[74fordman]

Ok so did the test with dynamic all the way down i get 34 ohms as you turn it up you can watch it climb get about to the half way point getting around 600 ohms it suddenly drops down to .8 ohms. Took it out to the truck put a power mic on it and it works fine so I'm assuming the dynamic is no good

 

[Handy Andy]

Drops down to 0.8 ohms?

Hmmm...Well if you have to use a power mike and you don't want to invest any more time into it, then enjoy.

But when the pot (Mike cord not connected) does that, it's telling you it's got a dead short in the wiring front that Jack to the board thru that Dynamike...

So I've posted some more info to help you if you want to get back to this...

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Uniden 66/68 and Cobra 25's pretty much share that same "Basic" Mic amp circuit.