PRO-2042 issue

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737mech

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Looking for help, I use my Pro-2042 sometimes to feed a stream. Lately I hear a pop every six seconds over the feed? Tried changing all cords involved and stopped using 13.8 VDC input and plugged in the A/C cord. All attempts no joy? There must be a cap or something going bad? Every 6 seconds pop over the the audio tape out not on the speaker though. Anyone have ideas what it could be?
 

kruser

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Looking for help, I use my Pro-2042 sometimes to feed a stream. Lately I hear a pop every six seconds over the feed? Tried changing all cords involved and stopped using 13.8 VDC input and plugged in the A/C cord. All attempts no joy? There must be a cap or something going bad? Every 6 seconds pop over the the audio tape out not on the speaker though. Anyone have ideas what it could be?
Do you have a small standalone amplifier (old stereo receiver maybe) that you can plug the audio lead into from the 2042 and see if the 6 second pop is still there when not hooked to the computer?
Basically, try a process of elimination and rule out components in hopes of finding the source.
 

kruser

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That's essentially the same as using a different audio amp!

With that ruled out, is the pop still present even when the feeds RF signal is off the air?
Any new scanners sitting near the 2042 or hooked in with the 2042 to the same antenna. The local oscillator from another scanner could be getting into the 2042.
 

kruser

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Sorry, that's what I meant to ask is if you were using a multicoupler or something with port isolation between radios if more than one radio.
It sounds like you are good in that area.

I sure can't think of anything specific.
I do agree something like a failing cap is likely figuring the age of a 2042 now, especially one that may have been powered on for years.

Good luck in your quest to find the source!
 

Ubbe

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Every 6 seconds pop over the the audio tape out not on the speaker though.
It then has to be a capacitor in the tape audio line that are leaking, as the audio are taken from the speaker output and then reduced down in level by a couple of resistors and a capacitor or two.

Try to resolder the components around the tape out jack to see if the heat will change anything. Wasnt' there a schematic available somewhere? I think I've seen one somewhere on the web.

It could be the big capacitor in series with the speaker, if you somehow have disconnected the internal speaker, as some people do to their feed scanners to stop any local audio, and do not use a bleeding resistor instead of a DC speaker load. The capacitor could build up a high DC voltage and then it conduct and make that pop sound and then starts to charge up again.

/Ubbe
 

Ubbe

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I couldn't find any Pro-2042 schematics but there's one for Pro-2035. I don't know the difference, it is mentioned that they look slightly different on the inside, but there's a constant audio level independent of volume on the tape out jack in the 2035. In that case there's an additional transistor and some passive components involved. As I remember the tape out where volume controlled on my Pro-2042 but I can be mistaken and it was some other vintage scanner of mine.


/Ubbe
 

tvengr

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Since you do not hear the pop on the speaker output, the problem must be related to the components in the tape output. Check which components are connected directly to the tape output jack. I would suspect leakage in an electrolytic capacitor or the driver transistor if there is one. Leakage can set up a time constant to cause the pop at regular intervals.
 

Ubbe

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There's no electrolytic capacitor in the tape out circuitry. Full schematics and service instruction are in the link I gave.
The smd compoments are on the underside of the circuitboard and I have had great succes fixing failures just be resolder smd components.

/Ubbe
 
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