I have just got around to a serious look at this, originally my
assumption was that it was the remote failing to work properly..

It is a large portable electric fan, three speed, timer to go off,
variable direction, with a random function. Control is via IR remote or
buttons on the fan. As the control IC it uses a SC8206 18 pin, with
green LED to indicate function and a tiny piezo buzzer.

The original problem was it sometimes failed to respond to the remote,
which became worse over time. Then the buttons on the unit itself
became iffy.

It uses a capacitive type power supply, with an X rated cap from the
mains, followed by diodes and resistors, a smoothing cap, then a zenor.
Which is supposed to provide 5v to the control system. With nothing
running, no LED's lit, it does provide the 5v, but that falls to around
3v when anything is powered, any current is drawn. I can turn it off
via a button on the unit, the remote will then work to turn it back on,
but no further response to remote - obviously because the rail voltage
has fallen to 3v.

Prace your bets on the likely failure mode? X rated cap, diode
rectifier, smoothing cap maybe? To be fair, the smoothing cap looks
fine and is rated 16v.

I'll get back to it with some serious diagnostics in a day or two.

On 04/06/17 15:16, Harry Bloomfield wrote:
I have just got around to a serious look at this, originally my
assumption was that it was the remote failing to work properly..

It is a large portable electric fan, three speed, timer to go off,
variable direction, with a random function. Control is via IR remote or
buttons on the fan. As the control IC it uses a SC8206 18 pin, with
green LED to indicate function and a tiny piezo buzzer.

The original problem was it sometimes failed to respond to the remote,
which became worse over time. Then the buttons on the unit itself became
iffy.

It uses a capacitive type power supply, with an X rated cap from the
mains, followed by diodes and resistors, a smoothing cap, then a zenor.
Which is supposed to provide 5v to the control system. With nothing
running, no LED's lit, it does provide the 5v, but that falls to around
3v when anything is powered, any current is drawn. I can turn it off via
a button on the unit, the remote will then work to turn it back on, but
no further response to remote - obviously because the rail voltage has
fallen to 3v.

Prace your bets on the likely failure mode? X rated cap, diode
rectifier, smoothing cap maybe? To be fair, the smoothing cap looks fine
and is rated 16v.

I'll get back to it with some serious diagnostics in a day or two.

If it is under voltage, but otherwise working the answer is to add a
little more capacitance to the 'X rated capacitor'.

You can solder a smaller cap across it, or replace it with a 10-20%
larger one.

If the zener starts smoking, you have gone too far.



--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen

On Sun, 04 Jun 2017 15:16:39 +0100, Harry Bloomfield wrote:

I have just got around to a serious look at this, originally my
assumption was that it was the remote failing to work properly..

It is a large portable electric fan, three speed, timer to go off,
variable direction, with a random function. Control is via IR remote or
buttons on the fan. As the control IC it uses a SC8206 18 pin, with
green LED to indicate function and a tiny piezo buzzer.

The original problem was it sometimes failed to respond to the remote,
which became worse over time. Then the buttons on the unit itself became
iffy.

It uses a capacitive type power supply, with an X rated cap from the
mains, followed by diodes and resistors, a smoothing cap, then a zenor.
Which is supposed to provide 5v to the control system. With nothing
running, no LED's lit, it does provide the 5v, but that falls to around
3v when anything is powered, any current is drawn. I can turn it off via
a button on the unit, the remote will then work to turn it back on,
but no further response to remote - obviously because the rail voltage
has fallen to 3v.

Prace your bets on the likely failure mode? X rated cap, diode
rectifier, smoothing cap maybe? To be fair, the smoothing cap looks fine
and is rated 16v.

I'd go for the smoothing cap. The X rated capacitors are usually only
there for interference suppression, and in any case they usually fail
with magic smoke.


--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On 04/06/17 17:11, Bob Eager wrote:
On Sun, 04 Jun 2017 15:16:39 +0100, Harry Bloomfield wrote:

I have just got around to a serious look at this, originally my
assumption was that it was the remote failing to work properly..

It is a large portable electric fan, three speed, timer to go off,
variable direction, with a random function. Control is via IR remote or
buttons on the fan. As the control IC it uses a SC8206 18 pin, with
green LED to indicate function and a tiny piezo buzzer.

The original problem was it sometimes failed to respond to the remote,
which became worse over time. Then the buttons on the unit itself became
iffy.

It uses a capacitive type power supply, with an X rated cap from the
mains, followed by diodes and resistors, a smoothing cap, then a zenor.
Which is supposed to provide 5v to the control system. With nothing
running, no LED's lit, it does provide the 5v, but that falls to around
3v when anything is powered, any current is drawn. I can turn it off via
a button on the unit, the remote will then work to turn it back on,
but no further response to remote - obviously because the rail voltage
has fallen to 3v.

Prace your bets on the likely failure mode? X rated cap, diode
rectifier, smoothing cap maybe? To be fair, the smoothing cap looks fine
and is rated 16v.

I'd go for the smoothing cap. The X rated capacitors are usually only
there for interference suppression, and in any case they usually fail
with magic smoke.


Not in the case when you want a wattless dropper from the mains without
involving a coil.





--
Outside of a dog, a book is a man's best friend. Inside of a dog it's
too dark to read.

Groucho Marx

Dried out capacitors. These so called lossless droppers using a capacitor
can be prone to the cap simply going low capacity, or in the case of an old
torch charger, going short and catching fire instead.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Harry Bloomfield" wrote in message
news
I have just got around to a serious look at this, originally my assumption
was that it was the remote failing to work properly..

It is a large portable electric fan, three speed, timer to go off,
variable direction, with a random function. Control is via IR remote or
buttons on the fan. As the control IC it uses a SC8206 18 pin, with green
LED to indicate function and a tiny piezo buzzer.

The original problem was it sometimes failed to respond to the remote,
which became worse over time. Then the buttons on the unit itself became
iffy.

It uses a capacitive type power supply, with an X rated cap from the
mains, followed by diodes and resistors, a smoothing cap, then a zenor.
Which is supposed to provide 5v to the control system. With nothing
running, no LED's lit, it does provide the 5v, but that falls to around 3v
when anything is powered, any current is drawn. I can turn it off via a
button on the unit, the remote will then work to turn it back on, but no
further response to remote - obviously because the rail voltage has fallen
to 3v.

Prace your bets on the likely failure mode? X rated cap, diode rectifier,
smoothing cap maybe? To be fair, the smoothing cap looks fine and is rated
16v.

I'll get back to it with some serious diagnostics in a day or two.

It happens that Bob Eager formulated :
I'd go for the smoothing cap. The X rated capacitors are usually only
there for interference suppression, and in any case they usually fail
with magic smoke.

No, in this case it is used as a 'voltage dropper', in series with the
load.

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

On Sun, 04 Jun 2017 18:38:08 +0100, Harry Bloomfield wrote:

It happens that Bob Eager formulated :
I'd go for the smoothing cap. The X rated capacitors are usually only
there for interference suppression, and in any case they usually fail
with magic smoke.

No, in this case it is used as a 'voltage dropper', in series with the
load.

Ah, then it's a toss-up really! Probably more likely to be that I guess.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On Sun, 04 Jun 2017 20:38:25 +0100, Harry Bloomfield
wrote:

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

No, a 50% change is a failure, not a tolerance.



--

Graham.
%Profound_observation%

On 04/06/17 21:17, Graham. wrote:
On Sun, 04 Jun 2017 20:38:25 +0100, Harry Bloomfield
wrote:

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

No, a 50% change is a failure, not a tolerance.



well that's semantics. Plenty of cheap caps used to be +-20% and many
electrolytics were -20%+50%.

If it was an old paraffin and paper dielectric, they dry out as well




--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".

On Sunday, 4 June 2017 21:47:25 UTC+1, The Natural Philosopher wrote:
On 04/06/17 21:17, Graham. wrote:
On Sun, 04 Jun 2017 20:38:25 +0100, Harry Bloomfield
wrote:

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

No, a 50% change is a failure, not a tolerance.



well that's semantics. Plenty of cheap caps used to be +-20% and many
electrolytics were -20%+50%.

If it was an old paraffin and paper dielectric, they dry out as well

X caps are plastic film, and shouldn't lose capacity or be anything like -50%.


NT

On 04/06/2017 23:09, wrote:
On Sunday, 4 June 2017 21:47:25 UTC+1, The Natural Philosopher wrote:
On 04/06/17 21:17, Graham. wrote:
On Sun, 04 Jun 2017 20:38:25 +0100, Harry Bloomfield
wrote:

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

No, a 50% change is a failure, not a tolerance.



well that's semantics. Plenty of cheap caps used to be +-20% and many
electrolytics were -20%+50%.

If it was an old paraffin and paper dielectric, they dry out as well

X caps are plastic film, and shouldn't lose capacity or be anything like -50%.

Many X-rated capacitors are of the self-healing variety. Each time the
self-healing takes place there is a loss of metalised film leading to a
reduction of capacitance. Look up polypropylene capacitors.

It suggests to me the voltage rating was marginal in the first place.

On Sunday, 4 June 2017 23:25:04 UTC+1, Fredxxx wrote:
On 04/06/2017 23:09, tabbypurr wrote:
On Sunday, 4 June 2017 21:47:25 UTC+1, The Natural Philosopher wrote:
On 04/06/17 21:17, Graham. wrote:
On Sun, 04 Jun 2017 20:38:25 +0100, Harry Bloomfield
wrote:

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

No, a 50% change is a failure, not a tolerance.



well that's semantics. Plenty of cheap caps used to be +-20% and many
electrolytics were -20%+50%.

If it was an old paraffin and paper dielectric, they dry out as well

X caps are plastic film, and shouldn't lose capacity or be anything like -50%.

Many X-rated capacitors are of the self-healing variety. Each time the
self-healing takes place there is a loss of metalised film leading to a
reduction of capacitance. Look up polypropylene capacitors.

It suggests to me the voltage rating was marginal in the first place.

Self healing causes very slight loss of capacity. To lose 50% to flashovers would take a very large number, indicating a cap faulty from day 1.


NT

It happens that formulated :
Self healing causes very slight loss of capacity. To lose 50% to flashovers
would take a very large number, indicating a cap faulty from day 1.

Possibly, I bought the fan around ten years ago.

Or indeed they can be an incorrectly marked batch that just about worked
when new but is now really useless.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"The Natural Philosopher" wrote in message
news
On 04/06/17 21:17, Graham. wrote:
On Sun, 04 Jun 2017 20:38:25 +0100, Harry Bloomfield
wrote:

Harry Bloomfield laid this down on his screen :
I'll get back to it with some serious diagnostics in a day or two.

ESR meter suggested the x-rated cap marked as 1uF was down in value to
426nF. Once replaced with a much older one which measured as 1026nF,
normal service was resumed fully. I would have thought the designer of
the circuit might have allowed for a bit more 'headroom' in the value
of the cap. I seem to remember this fan's remote operation was never
100% even when new, so maybe the cap began life well below its proper
value.

No, a 50% change is a failure, not a tolerance.



well that's semantics. Plenty of cheap caps used to be +-20% and many
electrolytics were -20%+50%.

If it was an old paraffin and paper dielectric, they dry out as well




--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".

On 05/06/17 08:09, Brian Gaff wrote:
Or indeed they can be an incorrectly marked batch that just about worked
when new but is now really useless.
Brian

Like the Labour party?

Its also possible as I discovered when testing 1000 optotransistors,
that it was just an outlier that slipped through testing.

(I plotted sensitivity versus sample size: What turned up was a
truncated bell curve, with truncation being the result of fcatory
rejection of substandards, except for two, that were well outside th
truncated zone).

--
The theory of Communism may be summed up in one sentence: Abolish all
private property.

Karl Marx