[MrFixr55]

Hi Dan,
Chances are that the 1000V cap is what they had available.

The cap in question couples the detector to the volume control. There is no B+ on that cap, and likely no more than about -20V or so AVC voltage and less than about -3V grid bias for the 1st audio amp. Most replacement mylar caps from suppliers to the hobby are rated for about 630V max. Non-electrolytic caps are rated for a maximum voltage. Fore a radio whose maximum B+ voltage is 250V, a 630V cap provides more protection from dielectric breakdown than a 400V cap.

However, electrolytics are rated in working voltage, so it is not good to use a 500 WV (Working Volt) cap in an AA5 radio whose rectifier generates about 150VDC. Maximum voltage tolerated by an electrolytic cap is not much higher than the working voltage, so take no-load voltage into consideration when picking electrolytic caps.