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Cobra 142GTL No Transmit or Receive

Lets ignore the receive for a minute. Receive signals are harder to trace than transmit ones, so let's make sure TX works first.

1 s-unit on a receiver with the transmitter into a dummy load sounds like it is making power, but lets be sure. Can you insert a watt meter between the radio and dummy load to see if we are getting the correct output power? And with that 1 s-unit in the other receiver, do you get audio with that or just a dead carrier?
 
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Can you power it from an external DC power supply using the power plug in the back instead of the onboard ac supply and recheck? You said you recapped, did you recap the power supply too?
 
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I feel like I need to take a moment to sort out the clues. The hum is in PA too, so the hum is not from loading down the supply (I'm not saying the supply isn't bad, I 100% agree with Cable guy, something is probably messed up there). I just worry about troubleshooting on a huge external supply since a bad final could damage the passthrough. I think we need to unhook the jumpers to the driver and final and test them individually.
 
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Once on an external supply, I would put a current meter inline with the jumpers (TP7 and TP8) one at a time and briefly key in SSB to ensure we are not drawing excessive current in one of them. (with mic gain down)
 
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I should have been a little clearer on my reply. No hum/hiss in PA audio.

And its not really a buzz it is more of low hum/hiss. Same level with onboard power supply and external power supply.

I will check the current at TP7 and TP8 and post results
 
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If there isn't a ridiculous amount of current flowing in either, we can reconnect them and do some voltage checks in AM. Im at work so forgive me if I drop out now and then.
 
Well I can't check current as the fuses in both of my DMMs are shot and I don't have any spares on hand. I will have to check and see if can find anywhere around here tomorrow that have them.

Hate to be bothering you while you are working...
 
CSA1863 said:
Hate to be bothering you while you are working...
Click to expand...
Not to worry, I have a pretty laid back job. Not bothering me at all. My down time can be spent how I see fit here, and that comes from the top. I just spent $215 on a tool (that I always wanted anyhow) so I can do something for them, and that sort of thing happens regularly. My picture has been on their employee of the month wall 3 times this year, so if anyone ever takes issue with how I spend my down time, they can shove it. Honestly, I'm here for the benefits alone, the pay sucks.

My suggestion was just a precaution, we can skip the current meter step. We can go straight to the AM voltage measurements if we are fast on the key. Lets get a voltage at the collector of the final and driver in AM.
 
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Awesome! Thats a good sign.

The no power issue might just be a bunch of screwdrivered cans.

Just to be sure, switch to SSB and get base voltage measurements on both (TX, mic gain down).

Edit: headed out the door soon, be home in about an hour.
 
TR39 2SC1306 RX 13.14 TX 5.98 TR41 2SC1969 RX 13.14 TX 5.37

Also checked TR38 2SC1973 RX 0 TX 8.33

re posted this as my shop cat laid on the keyboard and some how deleted the original.
 
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