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KLH Model 21 help
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MitchSF
Jul 27, 2001, 3:34:43 PM7/27/01
to
Hi,
I'm almost finished restoring a KLH Model 21. I replaced three transistors
on the RF board and it now works!
I'm almost finished restoring a KLH Model 21. I replaced three transistors
on the RF board and it now works!
The only problem left is a hum from the audio board. I disconnected it from
the input to the board so I'm sure it's not coming from anywhere else. I
replaced the filter capacitor and all electrolytics on the audio board and
it's a little quieter, but still there. The level of the hum doesn't change
with the volume control.
Any hints would be appreciated!
Thanks,
Mitch
M. Green
Jul 27, 2001, 10:16:47 PM7/27/01
to
For some reason the power supply is still noisy, or there is some AC ground
looping. If you can use a scope, you can measure the supply rail to see if
it does have hum on it.
looping. If you can use a scope, you can measure the supply rail to see if
it does have hum on it.
There is a possibility that there is an open ground somewhere, or a shield
that is not right. Also if there is an AC ground loop, or a leakage in the
power transformer, this will cause some AC hum in the sound...
--
======================
Mary Green
maryg...@hotmail.com
======================
MitchSF <mit...@coresolutionsgroupDELETETHIS.com> wrote in message
news:9jsfoq$hje$1...@slb6.atl.mindspring.net...
craig osborn
Jul 27, 2001, 11:56:36 PM7/27/01
to
The black plastic cased caps they used in some models had problems.
JEFF
MitchSF wrote in message <9jsfoq$hje$1...@slb6.atl.mindspring.net>...
JEFF
MitchSF wrote in message <9jsfoq$hje$1...@slb6.atl.mindspring.net>...
audio...@gmail.com
Mar 16, 2018, 10:22:48 AM3/16/18
to
Trevor
Mar 17, 2018, 2:44:36 PM3/17/18
to
Trevor.
~misfit~
Mar 17, 2018, 8:08:49 PM3/17/18
to
It's good to have a knowledgeable person posting here so let's not be too
harsh...
--
Shaun.
"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)
Trevor
Mar 18, 2018, 3:12:49 AM3/18/18
to
On 18/03/2018 11:08 AM, ~misfit~ wrote:
> Once upon a time on usenet Trevor wrote:
>> On 17/03/2018 1:22 AM, audio...@gmail.com wrote:
>>> On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote:
>>>> Hi, I'm almost finished restoring a KLH Model 21. I replaced three
>>>> transistors on the RF board and it now works!
>>>>
>>>> The only problem left is a hum from the audio board. I
>>>> disconnected it from the input to the board so I'm sure it's not
>>>> coming from anywhere else. I replaced the filter capacitor and all
>>>> electrolytics on the audio board and it's a little quieter, but
>>>> still there. The level of the hum doesn't change with the volume
>>>> control.
>>>>
>>>> Any hints would be appreciated!
>>>>
>>>> Thanks, Mitch
>>>
>>> Hi Mitch. The power supply filters, either of the black color
>>> are/were a common failure item. They should be replaced. However,
>>> note that the positive terminal was marked with the stripe as we
>>> would now associate with the negative terminal. It is also important
>>> that you do not increase the value of these capacitors as the power
>>> supply can't handle the extra in-rush and operational paramete5rs.
>>> Mark - Former National Service Manager, KLH Cambridge.
>>
>> Wonder whether he even still has it 17 years later? :-)
>>
>
> Once upon a time on usenet Trevor wrote:
>> On 17/03/2018 1:22 AM, audio...@gmail.com wrote:
>>> On Friday, July 27, 2001 at 2:34:43 PM UTC-5, MitchSF wrote:
>>>> Hi, I'm almost finished restoring a KLH Model 21. I replaced three
>>>> transistors on the RF board and it now works!
>>>>
>>>> The only problem left is a hum from the audio board. I
>>>> disconnected it from the input to the board so I'm sure it's not
>>>> coming from anywhere else. I replaced the filter capacitor and all
>>>> electrolytics on the audio board and it's a little quieter, but
>>>> still there. The level of the hum doesn't change with the volume
>>>> control.
>>>>
>>>> Any hints would be appreciated!
>>>>
>>>> Thanks, Mitch
>>>
>>> Hi Mitch. The power supply filters, either of the black color
>>> are/were a common failure item. They should be replaced. However,
>>> note that the positive terminal was marked with the stripe as we
>>> would now associate with the negative terminal. It is also important
>>> that you do not increase the value of these capacitors as the power
>>> supply can't handle the extra in-rush and operational paramete5rs.
>>> Mark - Former National Service Manager, KLH Cambridge.
>>
>> Wonder whether he even still has it 17 years later? :-)
>>
>
> Probably not - at least not with the issue still (however somebody might...)
>
> It's good to have a knowledgeable person posting here so let's not be too
> harsh...
True, might help someone else, and I wouldn't want to discourage that.
>
> It's good to have a knowledgeable person posting here so let's not be too
> harsh...
I'm just amazed at how many people answer 20 year old posts because they
don't even realise it. :-)
Trevor.
~misfit~
Mar 18, 2018, 10:05:12 PM3/18/18
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actually use usenet - they use parasitic web forums that don't delete old
posts in an effort to appear to have lots of content.
Cheers,
Trevor
Mar 19, 2018, 5:35:59 AM3/19/18
to
the date was still shown somewhere? But then I've never used it myself.
Trevor.
~misfit~
Mar 19, 2018, 8:01:57 PM3/19/18
to
for an old post. The bastards took over Deja news archives and butchered
them!
geoff
Mar 21, 2018, 6:04:20 AM3/21/18
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geoff
~misfit~
Mar 24, 2018, 1:43:09 AM3/24/18
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> - you're everywhere !
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