I'm not certain that I really need a new ammeter or, if I do replace the current meter, whether I need a shunt. The 10-amp power supply is quite old (1966), but while the DC voltage output is on target, I can't get any response from the ammeter with a good multimeter (Beckman Circuitmate) attached. What makes me think that a new meter would not require a shunt is the fact that the wires serving the meter are 20 ga., less than a millimeter thick. I would think they would evaporate if asked to carry 10 amps. I don't have a schematic for the power supply, unfortunately.