Problem with tuning knob on Lowe HF 150.
 

Hi ,
Is there anybody have experince of a Lowe HF-150? On mine there is a
"crunchy sound" from the speaker when you turn the tuning knob.
It has been so from the beginning.When I have my fingertips on the upper
part of the case the crunchy sound reduces.
Is this phenomen normal for the HF-150 or it should be quite when you turn
the tuning knob?
Shall the tuning knob be connect to earth?
Thankful for all help
Lars

It shouldn't happen so long as you're listening at normal volume
levels, though the user's manual does state that you can expect some
vibration to occur if you turn the volume up high.

The solution is to get a decent external speaker. You ought to use an
external speaker anyway. Only an external speaker will do justice to
the high quality audio produced by the 150.

Steve

Hi Steve
I don't think the problem is feedback vibration from the speaker. I have
listen even in headphones and then the speaker is quite.It is when I turn
the tuning knob I can hear a rassle sound even in the headphones.
/Lars
skrev i meddelandet
ups.com...
It shouldn't happen so long as you're listening at normal volume
levels, though the user's manual does state that you can expect some
vibration to occur if you turn the volume up high.

The solution is to get a decent external speaker. You ought to use an
external speaker anyway. Only an external speaker will do justice to
the high quality audio produced by the 150.

Steve

It could be the bypass caps at the encoder inputs of the MCU, but more
probable is either noisy series diodes at the Channel A and B encoder
outputs or a noisy tuning encoder. Looking at mine, it appears to be a
mechanical encoder vs an optical unit. Another thing to check are the bulk
decoupling capacitors on the front panel display board. If the MCU isn't
properly bypassed because of degraded 'lytic caps you could be experience
ground bounce. It shouldn't be too bad to find, but I have had repairs in
the past that have started out as "a ten minute job".

Pete

"Lars Brandt" wrote in message
...
Hi ,
Is there anybody have experince of a Lowe HF-150? On mine there is a
"crunchy sound" from the speaker when you turn the tuning knob.
It has been so from the beginning.When I have my fingertips on the upper
part of the case the crunchy sound reduces.
Is this phenomen normal for the HF-150 or it should be quite when you turn
the tuning knob?
Shall the tuning knob be connect to earth?
Thankful for all help
Lars

"Lars Brandt" wrote in message
...
Hi Steve
I don't think the problem is feedback vibration from the speaker. I have
listen even in headphones and then the speaker is quite.It is when I turn
the tuning knob I can hear a rassle sound even in the headphones.

Are you using an external antenna with a decent RF ground? Not unusual to
hear encoder noise when using the atached whip and internal preamp.
Grounding the RX will eliminate this.

Dale W4OP

Could it be it only needs cleaning with some tuner cleaner fluid?
cuhulin

I didn't realize that this could happen under these conditions. I use a
Radio Shack loop antenna and it works ok on the MW band, but maybe the
antenna noise overrides this phenonemom.

Pete

"Dale Parfitt" wrote in message
news:2cs%d.6013$uw6.1020@trnddc06...

"Lars Brandt" wrote in message
...
Hi Steve
I don't think the problem is feedback vibration from the speaker. I have
listen even in headphones and then the speaker is quite.It is when I turn
the tuning knob I can hear a rassle sound even in the headphones.

Are you using an external antenna with a decent RF ground? Not unusual to
hear encoder noise when using the atached whip and internal preamp.
Grounding the RX will eliminate this.

Dale W4OP

No I use a whip antenna and no ground connection.
Is it neccesary to connect RX to ground? I have no good ground connection in
my flat.
So it is normal with noise from the tuning knob if I don't have connetion to
ground?
//Lars
"Dale Parfitt" skrev i meddelandet
news:2cs%d.6013$uw6.1020@trnddc06...

"Lars Brandt" wrote in message
...
Hi Steve
I don't think the problem is feedback vibration from the speaker. I have
listen even in headphones and then the speaker is quite.It is when I
turn
the tuning knob I can hear a rassle sound even in the headphones.

Are you using an external antenna with a decent RF ground? Not unusual to
hear encoder noise when using the atached whip and internal preamp.
Grounding the RX will eliminate this.

Dale W4OP

Some of my old radios make a raspy.skritticy noise when I tune the dial
knob and or the on/off/volume control knob.Sometimes I squirt a little
dab of tuner cleaner stuff (or even WD-40) from a spray can and the
noise stops for a while.I don't know that much,but I do not believe it
is normal for any radios to make any noises that are abnormal when
tuning the dial knobs or the on/off/volume control knobs.I could be
mistaken though.I do definetly know WD-40 works great for my old
arthritis fingers.
cuhulin

The balanced mixer module acts as a microphone.

On Mon, 21 Mar 2005 17:59:18 GMT, "Lars Brandt"
wrote:

No I use a whip antenna and no ground connection.
Is it neccesary to connect RX to ground? I have no good ground connection in
my flat.
So it is normal with noise from the tuning knob if I don't have connetion to
ground?
//Lars
"Dale Parfitt" skrev i meddelandet
news:2cs%d.6013$uw6.1020@trnddc06...

"Lars Brandt" wrote in message
...
Hi Steve
I don't think the problem is feedback vibration from the speaker. I have
listen even in headphones and then the speaker is quite.It is when I
turn
the tuning knob I can hear a rassle sound even in the headphones.

Are you using an external antenna with a decent RF ground? Not unusual to
hear encoder noise when using the atached whip and internal preamp.
Grounding the RX will eliminate this.

Dale W4OP

Thank you everybody for all tips. I think its ok now.I found a screw behind
the tuning knob on the front. When I removed the screw, there was no noise
anymore.
Another question, how can I get loose the potentiometer knob? I think it is
glued.
//Lars

"David" skrev i meddelandet
...
The balanced mixer module acts as a microphone.

On Mon, 21 Mar 2005 17:59:18 GMT, "Lars Brandt"
wrote:

No I use a whip antenna and no ground connection.
Is it neccesary to connect RX to ground? I have no good ground connection
in
my flat.
So it is normal with noise from the tuning knob if I don't have connetion
to
ground?
//Lars
"Dale Parfitt" skrev i meddelandet
news:2cs%d.6013$uw6.1020@trnddc06...

"Lars Brandt" wrote in message
...
Hi Steve
I don't think the problem is feedback vibration from the speaker. I
have
listen even in headphones and then the speaker is quite.It is when I
turn
the tuning knob I can hear a rassle sound even in the headphones.

Are you using an external antenna with a decent RF ground? Not unusual
to
hear encoder noise when using the atached whip and internal preamp.
Grounding the RX will eliminate this.

Dale W4OP

The potentionmeter knob might have a tiny little set screw that holds it
onto the shaft.
cuhulin

This was discussed a few months back and I seem to recall that the cap of the
knob was removable; which allowed access to a screw which would loosen the knob.
I have encountered other knobs that work this way so that might be the answer.

Although I can get a knife edge under the end cap of mine, it does not seem to
want to pop off, and I am not inclined to experiment with much force.

A search of the archives might confirm the answer.

Dave


Lars Brandt wrote:

Thank you everybody for all tips. I think its ok now.I found a screw behind
the tuning knob on the front. When I removed the screw, there was no noise
anymore.
Another question, how can I get loose the potentiometer knob? I think it is
glued.
//Lars

"David" skrev i meddelandet
...
The balanced mixer module acts as a microphone.

On Mon, 21 Mar 2005 17:59:18 GMT, "Lars Brandt"
wrote:

No I use a whip antenna and no ground connection.
Is it neccesary to connect RX to ground? I have no good ground connection
in
my flat.
So it is normal with noise from the tuning knob if I don't have connetion
to
ground?
//Lars
"Dale Parfitt" skrev i meddelandet
news:2cs%d.6013$uw6.1020@trnddc06...

"Lars Brandt" wrote in message
...
Hi Steve
I don't think the problem is feedback vibration from the speaker. I
have
listen even in headphones and then the speaker is quite.It is when I
turn
the tuning knob I can hear a rassle sound even in the headphones.

Are you using an external antenna with a decent RF ground? Not unusual
to
hear encoder noise when using the atached whip and internal preamp.
Grounding the RX will eliminate this.

Dale W4OP

If the head of that philips screw is interfering with something,perhaps
file the head of the screw down and hacksaw a slot in the head of the
screw so a flat blade screwdriver can be used to tighten the screw back
down.I have worked on screws a lot of times before with hacksaws and
files.And hammers and chisels and cussin them damn screws and bolts out
:{)
cuhulin

Another question, how can I get loose the potentiometer knob? I think it is
glued.
//Lars

Not near my hf150 now, but I changed out the pot (noisy) a year ago &
don't seem to remember any screw on the volume knob. I seem to
remember just pulling it off? I may be wrong, but I don't remember
EVER having forgotten anything ;)

I do remember the cursed design virtually requires disassembly &
unsoldering of every part on the board before the volume control could
be removed. Not quite but extremely poor placment of the volume pot.

Robert