Manrose timer fan circuit diagram?

[mattylad]

Has anyone got a circuit diagram for the timer PCB that looks like this please?
I cannot find one after several searches.

S0meone wants me to look at repairing it so I said I'd have a look into it.
(the above picture is of the same PCB but not the actual one, just something pulled off the net

 

[JohnW2]

Has anyone got a circuit diagram for the timer PCB that looks like this please? .... I cannot find one after several searches. ... S0meone wants me to look at repairing it so I said I'd have a look into it. (the above picture is of the same PCB but not the actual one, just something pulled off the net

This is a circuit diagram (plus explanation of operation) I created by dissecting various timer fans in the fairly distant- pretty old ones, but probably hasn't changed much, if at all. As one might expect, it's usually one of the two electrolytics which dies, but there is also sometimes thermal damage originating from the 22k/24k dropper.
Hope this helps.

 

[mattylad]

Thank you.

 

[SFK]

I have fixed that very same circuit board twice now.
Both times I changed the smaller 47uF (left hand) capacitor and it came back to life (there was obvious sign that the capacitor had failed - ie no domed top).

For me it was just the smaller capacitor (47uF, 16V, electrolytic) that was a fault - and in my opinion they used a too low voltage capacitor. However both times I changed like for like because I had that value of capacitor to hand, and was worried the next voltage up would not physically fit in the small space.
SFK

 

[ebee]

Would it not have been better pratice to just disconnect pin 3 of IC1d ? to leave the inputs fed and not "floating" , I thought that was the general convenntion!

 

[Harry Bloomfield]

As one might expect, it's usually one of the two electrolytics which dies, but there is also sometimes thermal damage originating from the 22k/24k dropper.

Near identicle, circuit on mine, with the addition of humidity sensing. It was that dropper resistor, which had failed on mine. I made up the value, and over-engineered it, with several resistors in parallel.

 

[Harry Bloomfield]

Would it not have been better pratice to just disconnect pin 3 of IC1d ? to leave the inputs fed and not "floating" , I thought that was the general convenntion!

It doubles the drive capability, combining the outputs of c and d.

 

[JohnW2]

Would it not have been better pratice to just disconnect pin 3 of IC1d ? to leave the inputs fed and not "floating" , I thought that was the general convenntion!

It would (I don't like 'floating inputs'!) - but there's also no harm in doing as Manrose (and 'Oracstar') originally did, in connecting pins 3 & 4, thereby putting IC1c and IC1d in parallel. However, as I noted on the diagram, in later Manrose versions, for some reason they left all three pins of IC1d 'floating'.

 

[JohnW2]

It doubles the drive capability, combining the outputs of c and d.

It does, but in this application that increased 'drive capability' is not required. In any event, as I said, in later versions Manrose completely disconnected IC1d - for whatever reason!

 

[JohnW2]

For me it was just the smaller capacitor (47uF, 16V, electrolytic) that was a fault - and in my opinion they used a too low voltage capacitor. However both times I changed like for like because I had the same value of capacitor to hand and was worried the next voltage up would not physically fit in the small space.

Yes, on at least a couple of occasions, it has been that electrolytic which had died in mine - although the problem was with the much larger ('timing') capacitor (also 16V rating) on at least one occasion.

The fact that the smaller electrolytic is perhaps more commonly the one to fail may possibly be related to the fact that it has voltage across it for all of its in-service life, whereas the larger one only has voltage across it whilst the 'trigger input' to the module is present. Mind you, electrolytics are funny things, and it wouldn't surprise me if they lasted longer with voltage always across them than when they spent long times without any voltage!

 

[JohnW2]

It would (I don't like 'floating inputs'!) - but there's also no harm in doing as Manrose (and 'Oracstar') originally did, in connecting pins 3 & 4, thereby putting IC1c and IC1d in parallel. However, as I noted on the diagram, in later Manrose versions, for some reason they left all three pins of IC1d 'floating'.

In case anyone is interested, this is a variant of the Manrose timer module which I encountered 'back then', in a Wickes-branded timer fan.

Because of (seemingly 'unnecessary') inclusion of a transistor, two of the gates of the IC became redundant - but none of the inputs of those two gates were left 'floating'.

 

[Harry Bloomfield]

but none of the inputs of those two gates were left 'floating'.

..and the outputs unnecessarily linked too!

 

[JohnW2]

..and the outputs unnecessarily linked too!

Indeed- but that does no harm

 

[mattylad]

I have fixed that very same circuit board twice now.
Both times I changed the smaller 47uF (left hand) capacitor and it came back to life (there was obvious sign that the capacitor had failed - ie no domed top).

For me it was just the smaller capacitor (47uF, 16V, electrolytic) that was a fault - and in my opinion they used a too low voltage capacitor. However both times I changed like for like because I had that value of capacitor to hand, and was worried the next voltage up would not physically fit in the small space.
SFK

The only cap that I did not have at work, so now I got to hunt for one.
I tried the fan itself and it's fine, changed the 470uf and it starts for a little then stops, so now I'm going to change the 47uf as long as I can find one.

Cheers.

 

[JohnW2]

The only cap that I did not have at work, so now I got to hunt for one.

It's only a 'smoothing' capacitor for the 15V supply, so it's value is far from critical - almost any electrolytic that would physically fit and had a working voltage over 15V (as has been suggested, ideally probably a bit higher than 16V!) ought to do the job.