View Single Post
Old 4th Oct 2019, 11:03 pm   #9
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: Bush SRP31D. Series resistor.

Why are you planning to use a diode and resistor?
I have had a bit of a look at the circuit diagram. You are replacing a STD C2D selenium rectifier with a votage drop of 1V? with a silicon diode with about the same voltage drop so no resistor should be necessary. Remember that the transformer will have a resistance approximtely the sum of the primary and secondary resistances.

A better replacement would be a UF4007 which switches faster and produces less noise than the 1N4007. It would be nice to know if any difference could be ascertained.

A resistor passing current for one fifth of the time will drop five times the voltage and dissipate five times the power compared to when it is passing the same average steady current.

Selenium rectifiers I have seen go high resistance in the forward direction and a diode placed across them will keep them cool and may allow sufficient reverse capability. This is a quick bodge with no extra terminal needed.

Last edited by TrevorG3VLF; 4th Oct 2019 at 11:06 pm. Reason: spelin
TrevorG3VLF is offline