Scanner sound issues? HELP

[Benzman66]

A friend of mine gave me a BC150. I hooked it up and plugged it in, programmed some channels, and sure enough, it will stop on transmissions, BUT you can't make out what is being said due to the amount of rushing white noise, which in this case is NOT the squelch.

Is this a bad cap/resistor issue or something else I am not thinking of. I hate junking it since it is in great shape, just want to make it work. LOL

Any ideas are appreciated.

 

[sjlamb]

The only accurate way to troublshoot the issue is to get a schematic for that model. I would then begin with testing for proper voltages from the input of the audio amp IC all the way up the line to the speaker leads. Remember that accurate testing of suspect components need to be performed "out of circuit". Leaky electrolytic caps are often the culprit. Not likely a bad resisitor unless you see one with obvious damage (burned open).

If you can't find or can't be bother with a schematic... you can try the "machine gun approach" of replacing all the caps in the auidio circuit AFTER confirming that the speaker is good by plugging in an external speaker.

 

[DaveIN]

Wow, that's a tough one. The squelch and volume controls are not easily exposed for cleaning and some of the components are not readily available. You could look for another used non-working one for some working parts, but I suspect you may get more out of it as a museum piece. Sounds like a fun restoration project.

 

[derevs]

What frequencies? The rushing white noise could simply be control channels which this unit cannot interpret.

 

[Benzman66]

All conventional, no control.
Squelch and volume controls are cleaned, and speaker has been tested ok, so the issue is definitely somewhere in the board. Any more ideas or a schematic available?

 

[SkipSanders]

Have you tried listening to the weather channels?

It's barely possible that whatever you're trying to listen to is DES encrypted, which just produces white noise (with a short tone at the end of transmissions, usually), but probably not.

 

[iMONITOR]

Bad, lose antenna connection?

 

[Benzman66]

I have been a scanner enthusiast for 35 + years, and now way deep into digital scanners too, this sound is DEFINITELY NOT control channels, encryption, etc.
This is definitely an issue with the audio circuit , but I am not sure what needs to be changed out.
And it does it on the weather channels too.

 

[sjlamb]

I have been a scanner enthusiast for 35 + years, and now way deep into digital scanners too, this sound is DEFINITELY NOT control channels, encryption, etc.
This is definitely an issue with the audio circuit , but I am not sure what needs to be changed out.
And it does it on the weather channels too.

Agreed..... a fault of this type on a scanner of this age will 90% of the time be associated with aged electrolytic caps within the audio circuit. Replaced caps can also be upgraded to the next higher voltage rating for better performance in most cases. Not likely an RF input issue as OP has already stated that scan does stop on active freqs.

 

[Benzman66]

An update.
After a few weeks, I decided to plug in the 150 and try it again. For some reason, you can now hear talk on the channels, but it is pretty distorted. You can make out what they are saying, but you have to really concentrate.

I also wired it up to a known working speaker and it sounds the same, so it isn't the speaker being bad.

In addition, now my old BC 250 is on the fritz. It worked pretty well, but now it won't accept frequencies. You can punch the numbers in, but when you press Ent, nothing changes, also, every freq is on 989.270.

Then,if you leave it on for awhile, the rolling zeros change to rolling L's and even the squelch won't work. Turn it off for awhile, and it works again. Any ideas?

My luck seems to be so bad on my old scanners. Let's hope my digital scanners stay safe!

 

[sjlamb]

An update.
After a few weeks, I decided to plug in the 150 and try it again. For some reason, you can now hear talk on the channels, but it is pretty distorted. You can make out what they are saying, but you have to really concentrate.

I also wired it up to a known working speaker and it sounds the same, so it isn't the speaker being bad.

You're issue here remains essentially the same.........as does the solution. Change out the audio coupling caps. Probably have values such as 47uf, 33uf and/or 220uf. If they're rated at 25v; upgrade them to 35v or 50v.

 

[Benzman66]

Thanks for the reply sjlamb. Now if I can figure out which ones they are. LOL