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Old 6th May 2019, 9:49 pm   #1
Johnbarn
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Default Hacker Herald noisy

My LW/MW Hacker Herald has developed a noisy output as if someone was blowing across the studio microphone. I thought it might be a bad contact at the 5pin plug or the wave change switch or even the volume or pots for bass and treble but gentle cleaning and contact cleanser hasn’t helped. Can anyone help me in looking further? The radio is receiving all stations normally but just has this annoying rumble in the background which can only be minimised by winding the bass back fully.
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Old 6th May 2019, 10:31 pm   #2
paulsherwin
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Default Re: Hacker Herald noisy

Does the noise vary with the volume control or is it at a constant level?
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Old 6th May 2019, 10:32 pm   #3
martin.m
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Default Re: Hacker Herald noisy

The problem is almost certainly caused by transistor T1 on the bottom audio panel. A BC108 can be used as a replacement.

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Old 6th May 2019, 10:38 pm   #4
Johnbarn
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Default Re: Hacker Herald noisy

The noise is constant and not dependent on volume setting.
Thank you to both Paul and Martin. I’ll source another BC148 or a BC108 as you suggest.
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Old 6th May 2019, 10:44 pm   #5
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Default Re: Hacker Herald noisy

Don't use another BC148 Lockfit. Use a different BC108 family transistor like a BC548. This is just a general purpose transistor and lots of other types will also work - 2N2222, 2N3904 etc.

https://en.wikipedia.org/wiki/BC108_family

Lockfits are commonly failing now and a forum search will find lots of threads about them.
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Old 7th May 2019, 11:22 am   #6
Andrewausfa
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Default Re: Hacker Herald noisy

Which Herald is it? RP10, RP30 or RP35?

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Old 7th May 2019, 8:19 pm   #7
Johnbarn
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Default Re: Hacker Herald noisy

Andrew, it’s a MW/LW Herald RP35 and thanks to Paul and Martin’s advices I have replaced T1 with a BC108 and it now sounds great!! Just the way a Hacker should. Thanks boys.
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