BPR-40 audio howl

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arlojanis
Posts: 1044
Joined: Mon Jan 28, 2002 4:00 pm

BPR-40 audio howl

Post by arlojanis »

I have seen several Mag One BPR-40 UHF with a receive audio howl if volume is above a whisper. I tried extra pad on back of speaker and a pad between VCO and metal chassis. Pads did not help. Is there a cure or fix?
"The world runs on radio."
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fineshot1
Posts: 1125
Joined: Wed Oct 12, 2005 5:13 am

Re: BPR-40 audio howl

Post by fineshot1 »

Might be a long shot but i would try this if no one else comes up with anything:

Sounds to me similar to a Maxtrac grounding issue i found in many maxtracs.
The maxtrac fix was to re-tork all the screws that held the pc boards down
to the metal chassis. These screws all had to be re-torked harder since over time
they had gotten looser and they all were screwed down to a ground point.

Try this to the main board but be careful to not over tork the screws. Just make
them all a little tighter.
fineshot1
NJ USA
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arlojanis
Posts: 1044
Joined: Mon Jan 28, 2002 4:00 pm

Re: BPR-40 audio howl

Post by arlojanis »

Screws were tight.
"The world runs on radio."
KI4LTX
Posts: 29
Joined: Tue Jul 17, 2007 11:42 am

Re: BPR-40 audio howl

Post by KI4LTX »

This is a common problem with older BPR-40s, or those that have been exposed to a lot of heat. The BPR-40 has two ceramic filters, one for wide band and one for narrow band. There is a cushion (Part Number 75012112001) that is placed on top of the two filters (they are side by side). When this cushion deteriorates, it allows the audio vibrations from the speaker to cause microphonics in the filters. Replacing the cushion should solve the problem.
Satelite
Posts: 670
Joined: Sat Aug 12, 2006 10:43 am

Re: BPR-40 audio howl

Post by Satelite »

Hello:
Just adding for info only to consider.
We had several older P100 portables develop the rx howl.
If volume was turned down many if not most times the rx howl would go away but higher volume made it happen and worse as volume control was turned up.
We had a number of things that seemed to fix the issue with the P100 radio.
Usualy one of the below fixed it for us.
Didn't necessarily take multiple fixes just normaly one of them.
Bad battery causing low current to operate correctly.
Changing out the case itself helped at times.
Changing out the voltage regulator.
And the above already mentioned make sure all grounds are clean and making very good contact.
Satelite
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