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Old September 11th 05, 05:37 AM
Pete KE9OA
 
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Default Lowe HF-250 dismantling

Does anybody know how to take this thing apart? I just picked up one of
these units. It has that dreaded "howling audio with low system gain"
problem for the first 10 minutes of operation.
The 100uF 10V bypass cap that is across the 8V line is bad (why did they use
an electrolytic cap this close to its rated limits in the first place?).
Anyway, I got to compare this receiver with my HF-150 and HF-225.
The 150 is the most sensitive, the 225 is next, and the 250 follows by a
close third place. With the preamplifier engaged, the 250 falls into second
place.
Measurements were made using a Boonton Model 103D RF generator.
If I could figure out how to get the 250 apart, the repair is a ten minute
job. Nice receiver, good build quality.

Pete


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Old September 11th 05, 02:28 PM
David
 
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On Sun, 11 Sep 2005 04:37:49 GMT, "Pete KE9OA"
wrote:


Does anybody know how to take this thing apart? I just picked up one of
these units. It has that dreaded "howling audio with low system gain"
problem for the first 10 minutes of operation.
The 100uF 10V bypass cap that is across the 8V line is bad (why did they use
an electrolytic cap this close to its rated limits in the first place?).
Anyway, I got to compare this receiver with my HF-150 and HF-225.
The 150 is the most sensitive, the 225 is next, and the 250 follows by a
close third place. With the preamplifier engaged, the 250 falls into second
place.
Measurements were made using a Boonton Model 103D RF generator.
If I could figure out how to get the 250 apart, the repair is a ten minute
job. Nice receiver, good build quality.

Pete


"Workshop"


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Old September 11th 05, 05:17 PM
 
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Pete - I took one apart a few years ago to fix a remote sensor problem
and it was a real pain to figure out but I finally did it.
Unfortunately I forgot the details! You may have noticed that the 250
just uses the 225 RF/IF circuit board with a different digital/uP
board.

Frank
K3YAZ

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Old September 11th 05, 06:13 PM
Pete KE9OA
 
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Hi Frank,

It looks as if the top panel is just pressure-fitted in place. If I remove
the control knobs and remove the two Allen head screws, the front panel
should pop off. After this happens, the top panel might just slide off.
I thought this was just a repackaged 225 with a pretty face. Oh
well............now I will have a small collection of Lowe receivers once I
get done with this one. The only ones I won't have will be the 125 and the
235, but this covers the general spectrum of Lowe receivers.
That white version of the 150 was pretty cool looking. Thanks for the
info........as long as I've got it apart, I will check the oscillator
calibration. I would be willing to bet that the test mode is very similar to
the other Lowe units.

Pete

wrote in message
oups.com...
Pete - I took one apart a few years ago to fix a remote sensor problem
and it was a real pain to figure out but I finally did it.
Unfortunately I forgot the details! You may have noticed that the 250
just uses the 225 RF/IF circuit board with a different digital/uP
board.

Frank
K3YAZ



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Old September 11th 05, 06:40 PM
Pete KE9OA
 
Posts: n/a
Default

I finally got the unit apart.........once you loosen up the front panel and
slide it out a bit you can carefully insert a small screwdriver into the
slot that runs along the back of the top panel. It is a press-fit. I've got
the bottom panel off................off the Radio Shack to buy a couple of
100uF caps!
You were correct Frank................this receiver uses the same board as
my HF-225.

Pete

wrote in message
oups.com...
Pete - I took one apart a few years ago to fix a remote sensor problem
and it was a real pain to figure out but I finally did it.
Unfortunately I forgot the details! You may have noticed that the 250
just uses the 225 RF/IF circuit board with a different digital/uP
board.

Frank
K3YAZ





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Old September 11th 05, 06:44 PM
David
 
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On Sun, 11 Sep 2005 17:13:19 GMT, "Pete KE9OA"
wrote:


Thanks for the
info........as long as I've got it apart, I will check the oscillator
calibration. I would be willing to bet that the test mode is very similar to
the other Lowe units.



Test mode?


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