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Re: Split rail regulated power supply

Posted by Lew (A) on November 9, 2006 at 07:35:19

In Reply to: Re: Split rail regulated power supply posted by Legendre on November 9, 2006 at 06:41:36:

Bill, I yield to your superior expertise and experience in these matters, but using a flashlight I peeked into the PS of my MP1 last night, to confirm what I thought I already knew. (I am too lazy to take it apart to resolve the question, and I wanted to play LPs last night anyway.) The HV supply in my MP1 apparently starts with a trafo that is approximately 250-0-250, i.e., ~500V with a center tap. (Perhaps this is what you mean by "dual secondaries", so my confusion about that particular term is a matter of semantics.) Anyway, the two "250V" leads from the trafo go to a single FWB rectifier (built from hexfreds and bypassed of course), and the center-tap or "0" wire is taken to ground. The B+ is taken from the positive output node of the bridge, then pi-filtered and sent to a SuperReg which is wired between the plus side of the supply and referenced to the center tap (ground). The B- is derived from the negative output node of the bridge, also pi-filtered and sent to a different SuperReg which is wired between the center tap (ground, wired to the "hot" input of the SuperReg) and the filtered output of the negative node of the bridge (connected to the "ground" side of the SR). The regulated B- output of this SR appears at the "ground" side of its output. Thus two SuperRegs are driven by one FWB rectifier using a center-tapped trafo which may or may not qualify as having dual secondaries, to derive the B+ and B-. To make the negative supply SR work, it has a discrete regulated -15V supply. (The positive supply SR also has its own discrete regulated +15V supply.) What have I got wrong?

Perhaps it's a good idea to note that if one wants to use the SuperRegs in this way, one must derive and install that -15V supply for the B- SuperReg plus a separate +15V supply for the B+. Otherwise it is a no-go.

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