[Hammarlund] SP-200 Power Supply Question

[Rodger]

Hi Joe,

The bias supply is negative with respect to ground so the filter caps 
for the bias supply will have the positive side grounded and the 
negative connected to the bias lead.  The schematic may be confusing 
because some of the early SuperPros were probably built with oil filled 
capacitors in the supply and they are not polarized like the 
electrolytic caps commonly used today.  Of course the caps for the main 
part of the supply will have the negative leads grounded.  For all the 
capacitors, try not to go much higher in value, especially for the first 
capacitor following the rectifier tube.  If you increase the value of 
this capacitor, it will increase the load on the transformer and tube 
and will greatly increase the output voltage.  For the capacitor on the 
output side of the filter (furthest from the tube) you can increase the 
value to reduce hum without increasing power supply load or output 
voltage. 

73, Rodger WQ9E

Normandy Park HSA wrote:
> I'm working on a factory power supply for an SP-200. It's the model with B+
> filtering of one 1 mfd cap and three 16 mfd caps and bias filtering of three 8
> mfd caps. It's in sort of rough shape but should clean up nicely.
>
> Do the bias caps have the + or - lead to ground? I'm confused because the
> schematic seems to shows that the - lead is grounded but I see a newer
> replacement cap in there that has the + lead to ground. (The replacement cap has
> the wrong capacitance and the wrong voltage rating, so I'm thinking it might
> have been added by a prior owner who was confused).
>
> Which lead is grounded on the bias caps? Once I know that, I can start the
> repair process.
>
> As always, thanks!
>
>
> Joe Connor
>
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