Uniden bearcat UBC 360clt no sound output

[Jedi134]

Hi I have inherited the above desktop scanner, all seems to work correctly but there is no sound output. The only sound I do get from the speaker is the beep confirmation when you press a key. No output from the headphone socket either. Not even radio static with squelch fully turned down, tried a reset by holding 2, 9, and hold buttons but still no sound, does anyone have any experience with these scanners, thanks.

[CapLeaker]

Open it up and post some high resolution straight shot pictures of the board(s) and add it using the attachment function.
In the mean time you can read this:
https://www.badcaps.net/forum/troubl...o-audio-repair

[CapLeaker]

by the sounds of it it must have an RX problem, since you can hear beeps.

[Jedi134]

Yes could well be RX problem as won't grab any frequency, not even a strong local radio station, just keeps on scanning, the beep however is crystal clear..

I have uploaded some photos as asked, maybe you can point in the right direction.

[R_J]

What are you using for an antenna? the telescpoing one that comes with it?

[CapLeaker]

Measure the resistance between the centre pin of the BNC connector (antenna) to the outside shield. Try using a AM loop antenna to receive something on the AM broadcast band. See what that does. On the first picture is all your RF and audio stuff. The 450khz receiver (AM/FM demodulator) is the JRC2552 IC next to the metal can. I wonder if it is just a certain band not working or if everything is dead. If everything is dead things aren't looking good unless you got a donor or spare parts (besides if you measure a short on the antenna).
I do have a BC340CLT here that I just fixed. On this one was a cap bad. On your picture it would have been the cap that is black. But I doubt it.

[CapLeaker]

Here is a schematic for a UBC355CLT. Close enough for the RF path's anyway...

[Jedi134]

What are you using for an antenna? the telescpoing one that comes with it?

Yes but I would have thought this would pick something up especially a strong radio station, I will try something else just to rule it out though.

[Jedi134]

Measure the resistance between the centre pin of the BNC connector (antenna) to the outside shield. Try using a AM loop antenna to receive something on the AM broadcast band. See what that does.

Same with AM band and loop antenna won't lock onto any frequency



On the first picture is all your RF and audio stuff. The 450khz receiver (AM/FM demodulator) is the JRC2552 IC next to the metal can. I wonder if it is just a certain band not working or if everything is dead. If everything is dead things aren't looking good unless you got a donor or spare parts (besides if you measure a short on the antenna).
I do have a BC340CLT here that I just fixed. On this one was a cap bad. On your picture it would have been the cap that is black. But I doubt it.

The black cap next to the heatsink with a KIA78/R09PI strapped to it. Some kind of voltage regulator. What was the fault you had to warrant replacing this cap? Looks like a 100uf 25v.
also what do these 2 pots do. RT2 and RT3

No short across antenna reading 1.4 Meg ohms

[Jedi134]

Here is a schematic for a UBC355CLT. Close enough for the RF path's anyway...

Thanks will have a look at them. Could it be a squelch problem, ie it's defaulted to max and is just by passing the scanned frequency??

[CapLeaker]

The caps around the 9V regulator are always a problem on the older scanners with long run times,

O.k. So you have no short on the antenna, good! Did you check the other bands? This step is important look at the schematic. The receiver has 5 bands! Each band is tuned for a specific frequency range.
So do you have a problem with the switching in between bands, a blown IF amps, PLL unlock, a mixer missing or that RX IC bad? Don't just screw around with pots that you don't know what they do, because then you probably need an alignment and you need specific tools to do so.

[CapLeaker]

Thanks will have a look at them. Could it be a squelch problem, ie it's defaulted to max and is just by passing the scanned frequency??

I doubt that.
I would be spraying an RF signal into the 455khz IF. If something comes out the speaker, it will tell you if the front end is damaged or not. Don't forget to check the 10.8Mhz IF.

[Jedi134]

Result it was the squelch pot.. reading 8Meg ohm in both directions, so I swapped over too the other pin.. I'm receiving the world now...only my squelch operates in the opposite direction. Thanks for all you help anyway.

[CapLeaker]

That's a rare one. Never encountered that on a Uniden scanner. Never the less a good fix!