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Rf sampler smoked out my radio
- Thread starter 805 california
- Start date
Well I have built RF samplers before and I can say 100% beyond any shadow of doubt that there is nothing wrong with that sampler as we can see from the picture. The ONLY way possible way for something connected to the antenna jack would burn out that trace (still not sure which trace it is and what components it connects too) is if C60 is shorted out. It is a DC blocker capacitor that keeps the DC power from the finals off the antenna jack. The other possibility is an Effed up PA jack. DC voltage flows thru the speaker output transformer in CB mode since it acts as a modulation transformer in TX mode. What components are connected to EACH end of the burnt trace.
Ok something else is going on!.
That damage is definitely reverse polarity .
And that sampler can't cause that damage.
The only other thing I can think of is voltage coming back down the negative from the peak powered meter or some strange earth loop .
Set everything up. but don't connect the patch cable between radio and sampler , check for volts between radio ground and sampler ground
I have seen this sort of thing occurring from center tapped transformers hooked up wrong . And 24 volt trucks centre tapped to negative and +24, works great until you find earth with the antenna connection.
Just noticed you said the ext speaker socket fried as well, has got to be volts coming down the braid.
That damage is definitely reverse polarity .
And that sampler can't cause that damage.
The only other thing I can think of is voltage coming back down the negative from the peak powered meter or some strange earth loop .
Set everything up. but don't connect the patch cable between radio and sampler , check for volts between radio ground and sampler ground
I have seen this sort of thing occurring from center tapped transformers hooked up wrong . And 24 volt trucks centre tapped to negative and +24, works great until you find earth with the antenna connection.
Just noticed you said the ext speaker socket fried as well, has got to be volts coming down the braid.
10-4 I will check it out and get back to you. I still don't get why it wasn't smoking when it wasn't connected to sampler. You would think it would smoke whether it was connected to the sampler or not and it only smoked connected to sampler...... process of elimination.
The way I had it set up was coax from radio to rf sampler, then dummy load screwed right on to sampler then bnc wire to scope. I didn't have a meter hooked up.
I bet it's a hot chassis possibly from the scope. Is the scope powered by a three prong AC plug and is the CB power supply powered that way as well? If not it is possible you may have a hot chassis which is when one side of the AC line is connected to the chassis. This can be quite dangerous. It can happen if a two prong plug is inserted the wrong way into an outlet or if the AC outlet is wired wrong. Take an AC voltmeter and CAREFULLY measure the voltage from the ground pin of the AC outlet(use the little screw that holds the coverplate on) and then CAREFULLY measure the chassis of both the radio and then the scope. One at a time and see if there is any voltage from the chassis to ground.
I used to have an old signal generator that had an old two prong plug with both blades the same size so it could plug in either way. After getting my teeth rattled a couple times from picking up the coax cable from it while leaning on a piece of gear I replaced the cord with a regular three prong grounded cord. End of the teeth rattling episodes.
Few years back the house had a bad earth. First noticed it taking a shower could feel the current. Checked my station ground to house earth, had 40 volts difference. redid the earth and tied all grounds together with a big bus bar. problem solved
that can do it. Another point to check is for any voltage AC or DC between the chassis of the radio and the scope chassis.
So the scope has three prongs. With scope, power supply and radio on ( radio doesn't light up anymore. From screw on Wall socket to scope I got 2.3 v ac, from screw to radio I got fluctuating from 36 v ac to ol and 11.4 volts DC. Is that normal?
The 11.4 volts is with the positive lead on the screw and the negative on the radio chassi