Ammeter issues

[Rowyrow]

HI,
I'm having issues with these ammeters. When I test them in the 1A port the reading goes off the scale but when I use the 5A port nothing happens the needle doesn't move at all. I'm thinking there might be something wrong with the wiring. Initially I though the resistors where blown because some of them has turned black but i relpaced them in one unit and it made no difference. Is there something I am missing , does it look like there is something else wrong with them? what else could go wrong with them? I have also included a picture of one of out blown micro ammeters which I have managed to fix because the problem was blaringly obviouse. Any help muchly appreciated, the physics teacher wants to use them next term even though we have multi meters ugh!

[Ocker]

It seems to me the large resistor ( lowest Ohms ) is "open circiit"
In an Ammeter They are shunt resistors parallel with meter.
But you must know what you are doing to replace shunts check meters by disconnecting shunts and seeing what mA drives the meter to full scale, then use a digital multimeter to measure the resistance of the meter than get back to me and we'll do the Maths

[smiley]

Row,

Bin them, and then give your teacher multimeters! Think of the advantages - if the little cherubs wire them up backwards they'll just get a negative reading, not a blown up meter!

OR, place the broken meter on the teacher's desk with a little note asking him/her how to fix it