A friend asked me to attempt to find a fault in a short-lived dehumidifier
that functioned well for 1 season, but failed to operate after being unused
until needed again.

The sensor for the relative humidity is a thin ceramic square with
interlaced finger patterns deposited on the ceramic (looks like a
VCR/camcorder dew sensor). This sensor is placed inside the front grille in
path of the incoming air flow (but inside a small vented plastic box).
As the humidity rises, the very high resistance decreases.

Searching the model number revealed that many owners have had the same
experience with this model, that the unit worked great for 1 season, then no
worky.

This Goldstar DH305 is a normal looking small dehumidifier with no digital
readout or other controls that would give the impression that it's a
complicated appliance.. only an Off/1-9/Max pot (no integral switch) and a
high-low fan speed rocker switch.

BTW, the wrap-around metal cover needs to come off to access the controller
board.

When turned on, the fan runs for maybe a couple minutes, then stops. The
unit will not do anything else unless turned off then back on, after which
the same action repeats.

The capture container float switch isn't a problem.. it works normally and
turns on the red panel LED to show that the bucket needs emptied, indicating
that the unit isn't going to operate until it's emptied.

As stated earlier, the Off/On is just a pot, and the varying resistance
turns the controller circuit on, and the 1-to-Max setting will determine the
amount of run time.

The controller circuit looks fairly simple until the solder side of the
board is seen.. yep, another example of unnecessarily complicated design,
IMO.

The underside of the board has about 30% of the area populated with surface
mount components, including a 87C809 8-bit microcontroller.

After determining that the pot, switch and other sensors are apparently
working (PTC, NTC components).. and the ciruit board soldering looks
reasonable, I forced the unit into operation by huffing moist breath onto
the humidity sensor, the way one does the Haaaaah on their eyeglass lenses
to clean them.

So, the unit is capable of operating normally, and I checked that the
controller relay, not the temperature protector, was cutting off the
compressor.
This isn't an expensive appliance (maybe $140 new), but since it's still
functional, I'll attempt to return it to "fairly normal" operation (gold
star, better than it was/is now).

The voltage across the humidity sensor is approximately 4V AC when dry
(well, that's relative to the ambient humidity), and the unit goes into
operation when the moisture causes the voltage to drop to approx 0.085V
(85mV), which may not be accurate if there is a delay involved for some
(unknown to me) reason.

I'm contemplating cleaning the sensor a couple of times (although it appears
to be perfectly clean), checking the cicuit for a resistor that's drifted
high in value.. or adding a parallel resistor of maybe 2-5 Megohm across the
sensor (to get the voltage level down to a reasonable range.

Information I have, regarding cleaning and calibration of humidity sensors
cautions against using certain chemicals such as ammonia, alcohol,
formaldehyde.. and suggests only using distilled water and drying in a clean
area (or perchloroethylene for contaminated sensors).

This effort could be somewhat simplified if I were using a calibrated RH
meter.. I have these, but they haven't been calibrated for over 6 years, so
I'm not confident of their accuracy. The Solomat manual includes a saturated
salt reference method but I haven't tried it.

An alternative option could be to install a mechanical strip-type sensor
with an integral microswitch.. I've seen old versions which have set-point
adjustments, but I don't think I have any.

--
Cheers,
WB
..............

"Wild_Bill" wrote in message
...
A friend asked me to attempt to find a fault in a short-lived dehumidifier
that functioned well for 1 season, but failed to operate after being unused
until needed again.

The sensor for the relative humidity is a thin ceramic square with
interlaced finger patterns deposited on the ceramic (looks like a
VCR/camcorder dew sensor). This sensor is placed inside the front grille
in path of the incoming air flow (but inside a small vented plastic box).
As the humidity rises, the very high resistance decreases.

Searching the model number revealed that many owners have had the same
experience with this model, that the unit worked great for 1 season, then
no worky.

This Goldstar DH305 is a normal looking small dehumidifier with no digital
readout or other controls that would give the impression that it's a
complicated appliance.. only an Off/1-9/Max pot (no integral switch) and a
high-low fan speed rocker switch.

BTW, the wrap-around metal cover needs to come off to access the
controller board.

When turned on, the fan runs for maybe a couple minutes, then stops. The
unit will not do anything else unless turned off then back on, after which
the same action repeats.

The capture container float switch isn't a problem.. it works normally and
turns on the red panel LED to show that the bucket needs emptied,
indicating that the unit isn't going to operate until it's emptied.

As stated earlier, the Off/On is just a pot, and the varying resistance
turns the controller circuit on, and the 1-to-Max setting will determine
the amount of run time.

The controller circuit looks fairly simple until the solder side of the
board is seen.. yep, another example of unnecessarily complicated design,
IMO.

The underside of the board has about 30% of the area populated with
surface mount components, including a 87C809 8-bit microcontroller.

After determining that the pot, switch and other sensors are apparently
working (PTC, NTC components).. and the ciruit board soldering looks
reasonable, I forced the unit into operation by huffing moist breath onto
the humidity sensor, the way one does the Haaaaah on their eyeglass lenses
to clean them.

So, the unit is capable of operating normally, and I checked that the
controller relay, not the temperature protector, was cutting off the
compressor.
This isn't an expensive appliance (maybe $140 new), but since it's still
functional, I'll attempt to return it to "fairly normal" operation (gold
star, better than it was/is now).

The voltage across the humidity sensor is approximately 4V AC when dry
(well, that's relative to the ambient humidity), and the unit goes into
operation when the moisture causes the voltage to drop to approx 0.085V
(85mV), which may not be accurate if there is a delay involved for some
(unknown to me) reason.

I'm contemplating cleaning the sensor a couple of times (although it
appears to be perfectly clean), checking the cicuit for a resistor that's
drifted high in value.. or adding a parallel resistor of maybe 2-5 Megohm
across the sensor (to get the voltage level down to a reasonable range.

Information I have, regarding cleaning and calibration of humidity sensors
cautions against using certain chemicals such as ammonia, alcohol,
formaldehyde.. and suggests only using distilled water and drying in a
clean area (or perchloroethylene for contaminated sensors).

This effort could be somewhat simplified if I were using a calibrated RH
meter.. I have these, but they haven't been calibrated for over 6 years,
so I'm not confident of their accuracy. The Solomat manual includes a
saturated salt reference method but I haven't tried it.

An alternative option could be to install a mechanical strip-type sensor
with an integral microswitch.. I've seen old versions which have set-point
adjustments, but I don't think I have any.

--
Cheers,
WB
.............





I recently tried to troubleshoot a Zenith dehumidifier that turned out ot be
a LG underneath. The humidy sensor was made by these guys

http://www.samyoungsnc.com/products/SYH-2R.pdf

and is capacitive in design. The board also has a thermistor with a 2wire
plus common wiring harness and sells for 27USD in Ohio.
--
They can have my command prompt when they pry it from my cold dead fingers.

Wild_Bill wrote in message
...



Have you tried an ex-vcr humidity/condensation sensor as they seem very
reliable

I've just remembered a problem with vcr (generally?) humidity sensors. I
tried one as a window condensation sensor to cut in fans to dispel window
condensation. If humidity was low then R was low ,and high for humid , but
if the sensor got wet from condensation it would go low and stay low until
dried out naturally or forced. Or maybe resistance the other way round but
they were literally humidity sensors , not moisture

I appreciate the tip GJ, and I had seen a replacement (suggested on a
forum).. actually it includes the harness assy with the sensor board, a cold
sensor and the mating connector for the float switch (for about the same
price not incl shipping).
http://www.appliancefactoryparts.com...deh umidifier

Did you use the replacement part, and has the dehumidifier worked for longer
than one season?

The sensor module in this DH305 unit also has a small thermistor (I think
for ambient temp, because generally, dehumidifiers aren't supposed to be run
when ambient is below about 60F), and a 3-wire lead.

BTW, the Samyoung PDF info states the sensor is resistive.

This appears to be the RH sensor in the DH305 model, with specs very similar
to the Samyoung in the PDF you provided:
http://www.sangshinec.com/eng/hum_ksh02.htm

The actual value of a used dehumidifier is fairly low, probably less than
50% of what a new one could be bought for, so spending $32 to repair a unit
worth about $40 doesn't appeal to me.. particularly since the next fault may
be only weeks away.
This is, after all, just another example of low grade consumer crap.

I didn't want to get into a research project, but that's typical of
repairing anything these days.
Trouble is.. I got curious (again).

I don't need/want repair work, and my friends understand that.
I prefer to spend my time on my stuff of higher quality and greater value.

--
Cheers,
WB
..............


"George Jetson" wrote in message
...
"Wild_Bill" wrote in message
...
A friend asked me to attempt to find a fault in a short-lived dehumidifier
that functioned well for 1 season, but failed to operate after being
unused until needed again.

The sensor for the relative humidity is a thin ceramic square with
interlaced finger patterns deposited on the ceramic (looks like a
VCR/camcorder dew sensor). This sensor is placed inside the front grille
in path of the incoming air flow (but inside a small vented plastic box).
As the humidity rises, the very high resistance decreases.




I recently tried to troubleshoot a Zenith dehumidifier that turned out ot
be a LG underneath. The humidy sensor was made by these guys

http://www.samyoungsnc.com/products/SYH-2R.pdf

and is capacitive in design. The board also has a thermistor with a 2wire
plus common wiring harness and sells for 27USD in Ohio.
--
They can have my command prompt when they pry it from my cold dead
fingers.

Yep.. I vaguely recall a VCR having a false problem with the Dew indicator
being on, and failing to operate, but that was a long time ago.

When I pried open the plastic capsule for the dehumidifier's RH sensor, a
VCR sensor was the first thing that occurred to me.
I remember playing around with some of the VCR dew sensors but hadn't
actually tried using them for any other uses.

If I manage to get this unit to operate safely and relatively normally, I'll
accept that it's good enough.. it may not operate quite as efficiently, but
I don't see that it was rated as a high-efficiency/energy star unit, anyway
(and I have the user manual that was supplied).
BTW, there's a caution, which states.. Don't drink the water from the
dehumidifier!

I've modified older models to just cycle the compressor on for a reasonable
time with the fan running continuously, and they captured a lot of moisture
from the air.. in fact, very close to their original quarts-per-day rating
when they were new.

That was the reason for the "unnecessarily overcomplicated" comment in my
original post.

If this unit had been manufactured with a mechanical film strip RH
sensor/switch, it likely would have operated normally until a major problem
developed, likely many years later.
But oh****no, the geniuses had to implement a microprocessor for a simple
appliance.

The consumers get it again.. BOHICA

--
Cheers,
WB
..............


"N_Cook" wrote in message
...
I've just remembered a problem with vcr (generally?) humidity sensors. I
tried one as a window condensation sensor to cut in fans to dispel window
condensation. If humidity was low then R was low ,and high for humid , but
if the sensor got wet from condensation it would go low and stay low until
dried out naturally or forced. Or maybe resistance the other way round but
they were literally humidity sensors , not moisture

"Wild_Bill" wrote in message
...
I appreciate the tip GJ, and I had seen a replacement (suggested on a
forum).. actually it includes the harness assy with the sensor board, a
cold sensor and the mating connector for the float switch (for about the
same price not incl shipping).
http://www.appliancefactoryparts.com...deh umidifier

Did you use the replacement part, and has the dehumidifier worked for
longer than one season?

The sensor module in this DH305 unit also has a small thermistor (I think
for ambient temp, because generally, dehumidifiers aren't supposed to be
run when ambient is below about 60F), and a 3-wire lead.

BTW, the Samyoung PDF info states the sensor is resistive.

This appears to be the RH sensor in the DH305 model, with specs very
similar to the Samyoung in the PDF you provided:
http://www.sangshinec.com/eng/hum_ksh02.htm

The actual value of a used dehumidifier is fairly low, probably less than
50% of what a new one could be bought for, so spending $32 to repair a
unit worth about $40 doesn't appeal to me.. particularly since the next
fault may be only weeks away.
This is, after all, just another example of low grade consumer crap.

I didn't want to get into a research project, but that's typical of
repairing anything these days.
Trouble is.. I got curious (again).

I don't need/want repair work, and my friends understand that.
I prefer to spend my time on my stuff of higher quality and greater value.

--
Cheers,
WB
.............


"George Jetson" wrote in message
...
"Wild_Bill" wrote in message
...
A friend asked me to attempt to find a fault in a short-lived
dehumidifier that functioned well for 1 season, but failed to operate
after being unused until needed again.

The sensor for the relative humidity is a thin ceramic square with
interlaced finger patterns deposited on the ceramic (looks like a
VCR/camcorder dew sensor). This sensor is placed inside the front grille
in path of the incoming air flow (but inside a small vented plastic
box).
As the humidity rises, the very high resistance decreases.




I recently tried to troubleshoot a Zenith dehumidifier that turned out ot
be a LG underneath. The humidy sensor was made by these guys

http://www.samyoungsnc.com/products/SYH-2R.pdf

and is capacitive in design. The board also has a thermistor with a
2wire plus common wiring harness and sells for 27USD in Ohio.
--
They can have my command prompt when they pry it from my cold dead
fingers.


My bad, the pdf I pointed you to was resistive but there was another that is
capacitive.

I got off the hook fixing this dehumidifier as its still under warranty.
The problem started 3 months after purchase and others report about 1 yr
before it occurs.

The symptoms were shutting down after 2 seconds and throwing a 01 error
code. The mfg doesn't have any online info about error codes. Many others
seem to be suffering this error as well.



--
They can have my command prompt when they pry it from my cold dead fingers.

In looking more closely at the controller board, I found that the 2 humidity
sensor leads are tied directly to the 87C809 uC pins 6 and 7.
Between the #6 and 7 pins there is a 1M ohm resistor (meas 994k) and pin 6
has a small smt cap to the circuit ground (-) of supply.

There is no reason to expect that the dehumidifier will last for several
years, even if the sensor is replaced, which may only mean that the sensor
may need replacing again next year.
There were numerous reported failures of these models after one year, so a
repair that returns the unit to a "good as new" level, only means that it's
likely to fail again next year.

The sensor manufacturer's specs show a voltage rating of 1V, and I've seen
4V AC present at the sensor (the sensor resistance decreases as humidity
increases).
I don't know, but I suspect that this may have caused a change/drift in the
sensor's characteristics.

This exercise in frustration is another example of the present level of
quality of consumer goods.
The race to the bottom has led us to the point of new levels of
consumerism.. where it's unreasonable to have any expectations of quality,
and the stores are always full of new crap to replace the old crap.
Shopping for new crap has become a form of recreation, at least here in the
US.. they can't build malls fast enough to satisfy the cravings.

This dehumidifier was essentially produced with the lowest cost parts
available (the electrolytics are 85C rated in an appliance that will
generate a lot of heat) which are then assembled with lead-free solder, and
rushed to a store near you.

This is the primary reason why I quit repairing stuff, even for friends.

--
Cheers,
WB
..............

"Wild_Bill" wrote in message
...
In looking more closely at the controller board, I found that the 2
humidity sensor leads are tied directly to the 87C809 uC pins 6 and 7.
Between the #6 and 7 pins there is a 1M ohm resistor (meas 994k) and pin 6
has a small smt cap to the circuit ground (-) of supply.

There is no reason to expect that the dehumidifier will last for several
years, even if the sensor is replaced, which may only mean that the sensor
may need replacing again next year.
There were numerous reported failures of these models after one year, so a
repair that returns the unit to a "good as new" level, only means that
it's likely to fail again next year.

The sensor manufacturer's specs show a voltage rating of 1V, and I've seen
4V AC present at the sensor (the sensor resistance decreases as humidity
increases).
I don't know, but I suspect that this may have caused a change/drift in
the sensor's characteristics.

This exercise in frustration is another example of the present level of
quality of consumer goods.
The race to the bottom has led us to the point of new levels of
consumerism.. where it's unreasonable to have any expectations of quality,
and the stores are always full of new crap to replace the old crap.
Shopping for new crap has become a form of recreation, at least here in
the US.. they can't build malls fast enough to satisfy the cravings.

This dehumidifier was essentially produced with the lowest cost parts
available (the electrolytics are 85C rated in an appliance that will
generate a lot of heat) which are then assembled with lead-free solder,
and rushed to a store near you.

This is the primary reason why I quit repairing stuff, even for friends.

--
Cheers,
WB
.............


Ok then stop fixing things, if you can. Most of the people here enjoy logic
problems and diagnosing broken stuff. Admit your a junkie just like the
rest of us, we have meetings every week.

--
They can have my command prompt when they pry it from my cold dead fingers.

I had already confessed.. my excuse, stated earlier, was that I got curious
(again).

Some of my really old SER posts mention the problems/pitfalls associated
with being inquisitive, and yes.. it's a life-long crusade/curse of sorts.

I don't buy expensive new high-end gear because when it fails (usually just
as soon as a cheap product will) the disappointment is always greater.

I'll buy quality used gear and make do with it.. but sometimes repairing
those free or $1 flea market/hamfest acquisitions can burn up a lot of time
and effort (research projects, as stated earlier).

--
Cheers,
WB
..............


"George Jetson" wrote in message
...

Ok then stop fixing things, if you can. Most of the people here enjoy
logic problems and diagnosing broken stuff. Admit your a junkie just like
the rest of us, we have meetings every week.

--
They can have my command prompt when they pry it from my cold dead
fingers.

Thank you *Franc.. you have the knack to be able to find just about anything
that gets mentioned.

I've been surprised many times by your abilities.

*(spelled correctly this time)

--
Cheers,
WB
..............


"Franc Zabkar" wrote in message
...

You can purchase the part (6877A30013R) at Sears for US$13.25:
http://www.searspartsdirect.com/part... t=6877A30013R

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.