Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Dave_s
 
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Default LCD Screen-black spots

My 440 Handy Talkee [HT], a Realistic HTX-404, has been sitting without
operating for 6 months. Now, the LCD display has a cluster of black
shapes centered vetically and in 3/8 inch from left edge even when the
HT is off or on. How can I makes these unwanted shapes go away?
Appreciate any hints. Thanks, Dave_s, 73, W6MIK.
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Just Another Theremin Fan
 
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Put sticky tape over the bits that should be there.

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Just Another Theremin Fan
 
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Put sticky tape over the bits that should be there.

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Replaced the damaged lcd display.

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Junior Member
 
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Now Dave, are you ‘rat sure that those are positioned “vetically” ? Now by my being blind to your
situation , e.g., not having the unit in hand for an eyeball QSO, could you confirm that that
condition is maintained even when there is no power or batteries in the unit.
(And even that thought process could be flawed in the respect of retentive charge in the ua
current levels and low voltage levels still being maintained by capacitive elements in the radio
for some time period after unpowering…..still adequate to effect a display action)
Also, was there any possibility of errant electrolyte seepage from defunt batteries involved.
My thinking would lean towards a contamination of a string of pixel elements in the LCD array
to cause that effect. Or, my most common finding is a loss of connectivity thru a connector to
the array.
This can usually be confirmed by powering up the display and enacting a moderate pressure to
the x-y planes of the displays front bezel assembly, hoping that will transfer enough movement
to the internal connector area to cause a corrective action in portions of the display, thus tipping
you off as to a display connection being the problem. Don’t..rpt…DON’T exert pressure to
the threshold of fracturing your displays glass front face, however.
Also there might be the possibility of pressing on the rear of the displays contact area via an
orange stick, wood dowel, etc., if access was obtained to inside the receiver housing after a partial
disassembly. Should you find a corrective manner by pixels changing in that prior probing procedure,
the most common cause of that condition is the manner of construction and the specific materiel
utilized in interfacing to the display. If you stored that unit in a heated environment (sun ravaged
car or storage building, etc)…..it is also more abject to failure. Should this exploratory action have
changed the display, get back to me and I’ll update you on what I usually find that fixes the situation.
73’s de Edd


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Dave_s
 
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Edd,
I checked the HTX-404 this morning and found following wrong.
1. BNC connector is mechanically loose but electrically OK.
2. TX output is 0.5 watt in Hi PWR mode with 13.8volts power.
Draws .2 Amps [3.6 watts] to create 0.5 watts RF out.
3. LCD display has spots but can read most of screen.

4. 12 hours storage disconnected from BP did not change spots.
Pressing LDC display glass/bezel did not change spots.
I did not open case and apply pressure
to LCD connector area from back of radio.

I am not going to put the money/labor into repairing this radio.
It's future use will only be as a receiving scanner.

Thanks for reply and diagnostic suggestions Edd,

73, W6MIK, Dave
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