08-09-2012, 03:22 PM
I am by no means an expert but these are some alternate ways to find out a ball park figure.
Looking at schematics in both Riders and Beitmans, shows different 620 models such as 37-620 and 38-620 and Bietmans says updated 620.
So I think the solution would be to know the rectifier type and know what the winding ratio is. It seems to be the transformers have a center tapped HV winding of 145ohms to CT and 155ohms to CT and the input is 5ohms So determine the ratio and apply the ratio to input voltage and you should arrive at AC output voltage.
I cannot see the voltage on the secondary clearly but it looks to be Either 660Volts or 860volts. Then look at a tube data sheet and see what the normal operating voltage range is. This should give you a clue to what voltage to consider. I know there is a rule of thumb in voltage for caps but don't remember what it is but I would say at least 20% more that the used voltage. I could be wrong though. I will see if I can find out. They used both a 5y4 but off hand I would chose 450 volts or even a 600volt to be safer. Looking at the tube manual says typical operational voltage 700 to 1000Volts Wow! But with loading and resistances it may be lower.
Looking at schematics in both Riders and Beitmans, shows different 620 models such as 37-620 and 38-620 and Bietmans says updated 620.
So I think the solution would be to know the rectifier type and know what the winding ratio is. It seems to be the transformers have a center tapped HV winding of 145ohms to CT and 155ohms to CT and the input is 5ohms So determine the ratio and apply the ratio to input voltage and you should arrive at AC output voltage.
I cannot see the voltage on the secondary clearly but it looks to be Either 660Volts or 860volts. Then look at a tube data sheet and see what the normal operating voltage range is. This should give you a clue to what voltage to consider. I know there is a rule of thumb in voltage for caps but don't remember what it is but I would say at least 20% more that the used voltage. I could be wrong though. I will see if I can find out. They used both a 5y4 but off hand I would chose 450 volts or even a 600volt to be safer. Looking at the tube manual says typical operational voltage 700 to 1000Volts Wow! But with loading and resistances it may be lower.
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