[Mathew Newton[_2_]]

I've got a Manrose SCF200TC inline extractor fan whose timer overrun facility has recently started only running for 5 minutes or so compared with the 20 minutes it used to.

I've not had chance to open the cover and see if there are any obvious telltale signs on the board, however I was wondering if anyone can advise on what would likely be the cause? I am assuming that the control circuit will be fairly crude in design.

Mathew

[Brian Gaff]

Maybe it uses a simple charging capacitor that has dried out via some kind
of timer and a relay.

Brian

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"Mathew Newton" wrote in message
...
I've got a Manrose SCF200TC inline extractor fan whose timer overrun
facility has recently started only running for 5 minutes or so compared
with the 20 minutes it used to.

I've not had chance to open the cover and see if there are any obvious
telltale signs on the board, however I was wondering if anyone can advise
on what would likely be the cause? I am assuming that the control circuit
will be fairly crude in design.

Mathew

[The Natural Philosopher[_2_]]

Mathew Newton wrote:
I've got a Manrose SCF200TC inline extractor fan whose timer overrun
facility has recently started only running for 5 minutes or so
compared with the 20 minutes it used to.

I've not had chance to open the cover and see if there are any
obvious telltale signs on the board, however I was wondering if
anyone can advise on what would likely be the cause? I am assuming
that the control circuit will be fairly crude in design.

Mathew

Mine had a pot inside you could adjust.

Possibly that's failed. Or got corrosion across it lowering its
(electrical) value,.



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rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

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On Monday, September 24, 2012 11:20:01 AM UTC+1, Mathew Newton wrote:
I've got a Manrose SCF200TC inline extractor fan whose timer overrun facility has recently started only running for 5 minutes or so compared with the 20 minutes it used to.



I've not had chance to open the cover and see if there are any obvious telltale signs on the board, however I was wondering if anyone can advise on what would likely be the cause? I am assuming that the control circuit will be fairly crude in design.



Mathew

Most likely culprits are a deteriorating electrolytic timing cap or a pot thats got dirty. You have a multimeter? You'll likely need one.


NT

[Bob Minchin[_4_]]

Mathew Newton wrote:
I've got a Manrose SCF200TC inline extractor fan whose timer overrun facility has recently started only running for 5 minutes or so compared with the 20 minutes it used to.

I've not had chance to open the cover and see if there are any obvious telltale signs on the board, however I was wondering if anyone can advise on what would likely be the cause? I am assuming that the control circuit will be fairly crude in design.

Mathew

Many lowcost timers needing 10s of seconds to 10's of minutes use cmos
chip 4020/4040/4060 variants with cheap ceramic capacitors and high
value resistors in the timing circuit which then count down by factors
of 2^n to give the required duration.
Often the capacitor fails or the high value resistor gets affected by
damp causing the oscillator to run too fast and the time shorten.

hth

Bob

[robgraham]

On Sep 24, 4:03*pm, Bob Minchin
wrote:
Mathew Newton wrote:
I've got a Manrose SCF200TC inline extractor fan whose timer overrun facility has recently started only running for 5 minutes or so compared with the 20 minutes it used to.

I've not had chance to open the cover and see if there are any obvious telltale signs on the board, however I was wondering if anyone can advise on what would likely be the cause? I am assuming that the control circuit will be fairly crude in design.

Mathew

Many lowcost timers needing 10s of seconds to 10's of minutes use cmos
chip 4020/4040/4060 variants with cheap ceramic capacitors and high
value resistors in the timing circuit which then count down by factors
of 2^n to give the required duration.
Often the capacitor fails or the high value resistor gets affected by
damp causing the oscillator to run too fast and the time shorten.

hth

Bob

Another component that is a weakness is the resistor that drops the
mains voltage. I don't know how that would have an impact on the
timing, but I've had several cheap electronic items where heat from
this resistor has damaged nearby parts.

Rob

[Mathew Newton[_2_]]

On Monday, September 24, 2012 12:54:04 PM UTC+1, (unknown) wrote:

Most likely culprits are a deteriorating electrolytic timing cap or a pot
thats got dirty. You have a multimeter? You'll likely need one.

I took the board out and all the components seemed fine, with the exception of a capacitor that had a definite pronounced bulge on the top (no apparent leakage or anything). Will try replacing that and see how I get on.

Thanks for all the help,

Mathew

[Mathew Newton[_2_]]

On Monday, September 24, 2012 10:24:16 PM UTC+1, Mathew Newton wrote:

I took the board out and all the components seemed fine, with the exception
of a capacitor that had a definite pronounced bulge on the top (no apparent
leakage or anything). Will try replacing that and see how I get on.

Just to follow-up on this; I replaced the suspect capacitor and all is now well.

Mathew

[dazseaton]

replying to Mathew Newton, dazseaton wrote:
Im having same trouble. removed my board and as you can see the large grey
resistor is red hot even though fan is off (except permanent live) and has
burnt the board. I'm assuming this is the one you changed?
https://www.homeownershub.com/img/cl

[John Rumm]

On 30/11/2017 21:14, dazseaton wrote:
replying to Mathew Newton, dazseaton wrote:
Im having same trouble. removed my board and as you can see the large grey
resistor is red hot even though fan is off (except permanent live) and has
burnt the board. I'm assuming this is the one you changed?
https://www.homeownershub.com/img/cl

No, he changed one of the capacitors.

Chances are the design simply runs that resistor hot. It does not look
damaged on your board even if it has "cooked" the cheap and nasty SRBP
PCB a bit.

See if you can tweak the timing with the pot on the board. If that does
not allow enough adjustment, then replace both the capacitors (the black
cylindrical things standing on end with silver tops). Use similar values
and make sure the working voltage is the same as (or higher than) the
ones already there.


--
Cheers,

John.

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On Thursday, 30 November 2017 21:14:05 UTC, dazseaton wrote:
replying to Mathew Newton, dazseaton wrote:
Im having same trouble. removed my board and as you can see the large grey
resistor is red hot even though fan is off (except permanent live) and has
burnt the board. I'm assuming this is the one you changed?
https://www.homeownershub.com/img/cl

what are the ring colours on the resistor?


NT

[Badger[_2_]]

replying to tabbypurr, Badger wrote:
Mine was marked red brown brown but measured at 21k ohms so guess it had
discoloured.

--
for full context, visit https://www.homeownershub.com/uk-diy...rd-836812-.htm

[Badger[_2_]]

replying to dazseaton, Badger wrote:
I stumbled on this thread and thought I'd add my observations on fixing one of
these boards which was either cycling on and off every few seconds or buzzing
and refusing to run the fan. The large resistor on mine also looks like it
runs hot but measured fine (23 k ohms), I tested and replaced the larger
capacitor (tested 370 uf instead of 470 uf, 8.4v esr) but this made no
difference. The solution was to replace the smaller capacitor next to the
potentiometer (even though the esr value etc tested better, the capacitance
had dropped to 24 uf instead of 47 uf), and this did the trick. Hope this
information helps someone.

--
for full context, visit https://www.homeownershub.com/uk-diy...rd-836812-.htm

[[email protected]]

On Thursday, 8 November 2018 15:44:05 UTC, Badger wrote:
replying to tabbypurr, Badger wrote:
Mine was marked red brown brown but measured at 21k ohms so guess it had
discoloured.

sounds like you need a doctor


NT

[Brian Gaff]

Probably used for hysteresis so the fan does not go on and off all the time
as it would if their was a simple detector.
Brian

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"Badger" m wrote in
message ...
replying to dazseaton, Badger wrote:
I stumbled on this thread and thought I'd add my observations on fixing
one of
these boards which was either cycling on and off every few seconds or
buzzing
and refusing to run the fan. The large resistor on mine also looks like it
runs hot but measured fine (23 k ohms), I tested and replaced the larger
capacitor (tested 370 uf instead of 470 uf, 8.4v esr) but this made no
difference. The solution was to replace the smaller capacitor next to the
potentiometer (even though the esr value etc tested better, the
capacitance
had dropped to 24 uf instead of 47 uf), and this did the trick. Hope this
information helps someone.

--
for full context, visit
https://www.homeownershub.com/uk-diy...rd-836812-.htm

[[email protected]]

On Thursday, 8 November 2018 16:17:55 UTC, Brian Gaff wrote:
"Badger" m wrote in
message ...
replying to dazseaton, Badger wrote:
I stumbled on this thread and thought I'd add my observations on fixing
one of
these boards which was either cycling on and off every few seconds or
buzzing
and refusing to run the fan. The large resistor on mine also looks like it
runs hot but measured fine (23 k ohms), I tested and replaced the larger
capacitor (tested 370 uf instead of 470 uf, 8.4v esr) but this made no
difference. The solution was to replace the smaller capacitor next to the
potentiometer (even though the esr value etc tested better, the
capacitance
had dropped to 24 uf instead of 47 uf), and this did the trick. Hope this
information helps someone.

Probably used for hysteresis so the fan does not go on and off all the time
as it would if their was a simple detector.
Brian

it's a hysterical fan controller