Help With a LED Clock Kit Please

[TheDutyPaid]

Hello all,

I put together this quite simple LED clock kit I got from ebay. When I powered it up it all works apart from 'D' segment being permanently lit.

I'm no stranger to hand soldering but circuits do confuse me a bit.

Any help would be great

 

[hexreader]

Welcome to the forum

It looks to me as if there is a defect in the PCB provided.

Maybe Google for others who have had the same problem with your board. I reckon there must be a lot of other dissatisfied customers out there.

Pin 15 of the Atmel 89C2051 chip should connect to segment D of the display, but does not.

See how pins 11 to 19 all have a PCB trace to the resistor pack except pin 15...

If you are feeling brave, solder a tiny wire link pin 15 of the 89C2051 to the resistor pack pin just above.

(or return the unit as faulty if you prefer not to take any risks)

Hope I got it right - follow my advice at your own risk - I will not resolve any issues if I turn out to be wrong. Maybe wait to see if others reply either agreeing or disagreeing before making any changes.

Good luck..

 

[AnalogKid]

Please post something: the schematic, a link to the assembly manual, whatever.

ak

 

[TheDutyPaid]

Here is a scan of the paper I got with it.

 

[AnalogKid]

The display pinouts in posts 4 and 5 are not the same.

ak

 

[TheDutyPaid]

The display pinouts in posts 4 and 5 are not the same.

ak

I have removed it now, at the time it looked the same lol, any rate picture is now up of the right circuit

 

[TheDutyPaid]

Pin 15 of the Atmel 89C2051 chip should connect to segment D of the display, but does not.

See how pins 11 to 19 all have a PCB trace to the resistor pack except pin 15...

If you are feeling brave, solder a tiny wire link pin 15 of the 89C2051 to the resistor pack pin just above.

Thank you hexreader, perfect advice.

Just added a blob of solder between the two pins and the clock is working perfect. Not sure how to set the different functions, but I am sure to work that out.

 

[73's de Edd]

No sign of that intereconnecting foil link path having EVER been there.
Not being so chancy, I would have gone for an intermediate current limiting resistor initially.
The piezo needs its cover peeled off.

73's de Edd

 

[TheDutyPaid]

No sign of that intereconnecting foil link path having EVER been there.
Not being so chancy, I would have gone for an intermediate current limiting resistor initially.
The piezo needs its cover peeled off.

73's de Edd

It goes to a resistor, and keeping the sticker on is a old way of limiting the volume.

It all works, I'm happy.