Atten APS3003S PSU Display Overclock

[vtl]

I know this is a reasonably popular DC power supply so heres a little hack I came up with to increase the display update rate of the voltage and current displays.

I was watching a mikeselectricstuff video and he briefly mentions hacking his power supply (completely different one) to increase the update rate.

I wondered if it was possible to change a clock crystal or component in the Atten PSU so I went digging inside and seeing what I could find. On the display board there are 2 large 7 segment LCD drivers, the Intercil icl7107cplz.

Datasheet link:
http://www.intersil.com/content/dam/Intersil/documents/fn30/fn3082.pdf

Looking at the datasheet, the last 3 pins (40, 39, 38) govern the clock rate of the driver. In the Atten power supply they have opted to use the RC option instead of a crystal and have chosen a frequency of around 45KHz with C=100pF. By lowering the capacitance it is possible to increase the frequency. I started out with a 47pF capacitor and it was a huge improvement. But I figure if somethings worth doing, its worth overdoing, so I cranked up the speed to a whopping ~200KHz with a 22pF cap.



I changed both C15 (Volt disp.) and C10 (Current disp.) on the display board which should give over 12 readings/sec. If you change the frequency as much as I did, chances are you'll need to do a calibration with the 2 trimpots on the back with a multimeter.

Overall worth doing if you own this power supply. Using the datasheet you can select a capacitor that suits you. (There are suggestions for 50/60Hz rejection)

Result:

[grenert]

Nice trick!  Looking at the datasheet, 200kHz is the max for 50Hz countries, and 240kHz for 60Hz countries.  It is interesting that in the ubiquitous ICL7106/7107 meters nobody ever seems to have this set up for a fast update rate.  I see that a 40kHz rate rejects both 50 and 60 Hz, and this gives the typical 2.5 updates/sec.  It is probably that they didn't want to design a different setup for each market.
I'm going to crank up my meters...

[McMonster]

Interesting. I haven't been specifically annoyed by the update speed in my 5S version, but I am planning to hack in a temperature regulator for the fan, because it's too noisy and always on full speed. I think I'll throw in this hack as well.