Hi,

I'm trying to build this 556 voltage divider/doubler/inverter but I can't get it to work.

In the photograph, ignoring the 1000pF surface mount ceramic cap I count 5 ceramic caps and 5 electrolytics, but the schematic shows 6 electrolytics.

I think there may be a mistake in the schematic and I'm struggling to see enough detail in the photo to work out which cap may be wrong.

Maybe to the professionals something sticks out like a sore thumb?

Cheers
Martin

 

EDIT:

I think that the problem might be with one of the 47uF capacitors from pin 5 on the -5V line or the 4148?

Basically I need a circuit that will give me +10V and -5V from a +5V supply. This circuit is measuring +11.8V and -4.38 so it's more likely there's something wrong with the 10v side.

 

OK. I think the odd one out is the ceramic capacitor near Pin 2 of the 556.

In the schematic I think this cap is shown as a 47uF electro and it maybe should be a 0.047uF ceramic (or a different value?)

It's the cap second from right that goes to a 4148 from 0V?

 

how can you expect precision from an unregulated supply? the output will vary with load.

 

Hello,

Did you connect pin 7 of the NE556?
This should be the ground pin.
(I do not see it in your schematic).

Bertus

 

how can you expect precision from an unregulated supply? the output will vary with load.

Hi,

The load is a 4116 RAM chip.

 

Yes. I have this outputting a voltage but I think the -5V may be too low. The +10V output actually measures 12v under load which is normal for a 4116.

I just can't work out why one of the electrolytics in the schematic has become a ceramic in the picture.

Thanks for your suggestion.

Hello,

Did you connect pin 7 of the NE556?
This should be the ground pin.
(I do not see it in your schematic).

Bertus

 

OK. I might do this a different way using 2 x ADM660 or something.
Thanks everyone.