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Mobile linear amplifier

Stomper

Aug 13, 2018
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My cb technician was trying to fix my linear because the builder is a complete joke. While following the builders advice the tuner tube made contact with the remote jack and now we cant get output power. The amp is drawing amperage as it should. Any help would be very appreciated. Also does this cap look burnt.
 

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Alec_t

Jul 7, 2015
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Welcome to EP!
Which cap where? The pics are unclear. Can you post sharp, well-lit close-up pics, as well as make and model details?
 

kellys_eye

Jun 25, 2010
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the tuner tube
Looks like a solid-state set to me - where the tube?

Got a schematic?

The cap looks ok - some of the lead insulation is broken off (bad construction practise) but in RF applications I'd be changing it anyway.
 

Stomper

Aug 13, 2018
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It's still at the techs shop. All I know is that it says MDC 3310% npo and it's on the output tuner. Amps get 55amps but no power to the transistors and we cant figure it out and the builder isn't helping
 

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kellys_eye

Jun 25, 2010
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Without a signal input you should be getting only 'standby' current draw - certainly not 55A!!!

What are you using to power the unit? Does the power supply have any current limiting facility?

I suspect there's a short in at least one pair of output transistors and at 55A you would normally be seeing smoke if this is the case...... measure the transistor terminal voltages and report back (base, emitter, collector).
 

Stomper

Aug 13, 2018
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Yea the power supplies meter reads 55a when keying but power isn't getting to the transistors.
 

kellys_eye

Jun 25, 2010
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but power isn't getting to the transistors.
???? Where the heck is '55A' going then?

13.8V?? if so then 55A equates to 760W and you should be able to 'make toast' from the radiated heat........
 

Stomper

Aug 13, 2018
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Wish I knew where it was going then maybe we could get power to the transistors..
 

Cannonball

May 6, 2017
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Does the power supply show 55A when the CB is in receiver mode or only when transmitting?
I sure would like to see a schematic on this amp.
 

duke37

Jan 9, 2011
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Run it for a few seconds then use a digital temperature detector (finger).

I suspect than the PSU cannot supply the voltage at 55A so the heating may be low.
 

kellys_eye

Jun 25, 2010
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An infra-red camera could reveal any hot spots (though with 760W going somewhere, a wet finger could do that :) ).
So could a piece of bread!

Anyway, I asked the OP to respond with some voltage measurements which we have yet to see.......
 
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