[[email protected]]

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..

[Trevor]

On 17/03/2018 1:22 AM, 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? :-)

Trevor.

[~misfit~[_3_]]

Once upon a time on usenet Trevor wrote:
On 17/03/2018 1:22 AM, 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? :-)

Trevor.

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...
--
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]

On 18/03/2018 11:08 AM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote:
On 17/03/2018 1:22 AM, 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.
I'm just amazed at how many people answer 20 year old posts because they
don't even realise it. :-)

Trevor.

[~misfit~[_3_]]

Once upon a time on usenet Trevor wrote:
On 18/03/2018 11:08 AM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote:
On 17/03/2018 1:22 AM, 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.
I'm just amazed at how many people answer 20 year old posts because
they don't even realise it. :-)

As you likely know it's usually because these days most people don't
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,
--
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]

On 19/03/2018 1:05 PM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote:
On 18/03/2018 11:08 AM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote:
On 17/03/2018 1:22 AM, 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.
I'm just amazed at how many people answer 20 year old posts because
they don't even realise it. :-)

As you likely know it's usually because these days most people don't
actually use usenet - they use parasitic web forums that don't delete old
posts in an effort to appear to have lots of content.


Yes I know, and many are from Google Groups, but I would have thought
the date was still shown somewhere? But then I've never used it myself.

Trevor.

[geoff]

On 18/03/2018 1:08 PM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote:
On 17/03/2018 1:22 AM, 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? :-)

Trevor.

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...


Jeeze Shaun - you stalking me or something - you're everywhere !

geoff

[~misfit~[_3_]]

Once upon a time on usenet geoff wrote:
On 18/03/2018 1:08 PM, ~misfit~ wrote:
Once upon a time on usenet Trevor wrote:
On 17/03/2018 1:22 AM, 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? :-)

Trevor.

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...


Jeeze Shaun - you stalking me or something

Says the man replying to me...

- you're everywhere !

I prefer omnipresent. ;-)
--
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)