Re: Ferrograph 4A: Restoration advice needed
n will be far less than 30, n is the turns or voltage ratio not the resistance ratio.
Eg: Let's assume that the transformer is on the 245 volt tap with 245 volts going in, therefore Vp = 245, Total Vs anode to anode (according to the manual) = 480 VAC therefore divide that by 2 which = 240 therefore n = 245/240 = 1.02 therefore n = 1.02
Rt = Rs+n squared*Rp…..(+ R1) R1 is any additional surge limiter that may be fitted, that can be omitted because none is shown in the schematic.
Rs = 210 (420 as measured/2) Rp = 7 (as measured) and n = 1.02
So, Rt = 210 + 1.02*7 = 217.14 Ohms for each leg or 2 X 217.14 Ohms if you like.
So far as I can make out.
Lawrence.
