[R-390] SP 600 fixes

[Perry Sandeen via R-390]

List,


 
Wrote: The risk you run is that it is a choke fed supply soon power-up those capacitors appear like a dead short on the B+. I had left thetube based rectifiers alone so that kept things from getting too"thunky" (power transformer noise). If I had solid stated therectifiers that might be a really bad thing to do to those chokes. 


 
There are two easy ways to prevent “thunky” with SSrectifiers.


 
The simpler way: add 10 Ohm .5W resistors to each SS diode inputfrom the transformer.


 
A better way: Use a CL-90 thermistor in rush current limiter.  This is better as it gives a slow warm-up tothe tubes as well as the B+.


 
Wrote: Just about everything else you can find a replacementfor in the '600, except for the transformer and the chokes and those littlefingers in the turret deck.


 
I don’t know about power transformer replacement.  


 
For the chokes, Triode Electronics sells a Dynaco replacementchoke rated 1.5Hy and 200mA for $17. A whole lot smaller.  You make up the for the lower inductance by farlarger and less expensive Electrolytic caps. For example a Nichicon 220uF/450Volts 105C rated for 10K hours for $6.50. An unintended side benefit is youtake a fair amount of weight out of the set.


 
I was able to get some higher rated new Nichicons at a hamfestfor $2.50


 
There is a sneaky workaround for the turret clips. Althoughthe ceramic base is completely filled with clips, careful examination of theschematic shows that some are not used. They can be relocated although it is a PITA.


 
Regards,


 
Perrier

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