[Doris The Diode]

Panel meters

I’m building the Sussex and have a Chinese Volt meter very similar to the ones used in the build model nr YB5135D which were bought on eBay but the range is 500V.
I can see various solder joints at the back where I guess one can alter the range of the meter and also the AC DC sign.
I’ve looked high and low for instructions for the back solder points but have not been able to find any.

Has anyone got any information as to these solder points and what values they alter?

I am specifically wanting to change my 500V meter to read 0-20V for the grid, I don’t intend to go any lower than this value and I am ok with it, just require some information how to change the range.

To add complication, R4 and R5 seem to have an influence on the value of range as I have the 200mV meter and it has different values there.
Perhaps someone has a 20V version and could pass on the value and solder points?

All the best,
DD