RAL-6 Power Supply Redesign

Discussion in '"Boat Anchor" & Classic Equipment' started by KG4MSR, Dec 2, 2018.

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  1. KG4MSR

    KG4MSR Ham Member QRZ Page

    Open to any input from y’all on the redesign of a CRV-20131 power supply for a RAL-6.

    Received a RAL-6 with power supply a few months back—going to fully go through each to get them operational.

    Started with the power supply—opened her up and joyously found that every sealed transformer, choke, and capacitor were leaking their guts out all over themselves and the chassis... so I've decided to scrap the guts and rebuild it completely.

    Looking at the power supply schematics:

    upload_2018-12-2_15-28-40.png

    I see the once necessary line input filters to minimize noise from shipboard power could be removed.

    R-201/V-201 on the primary aren’t necessary (and eat up some extra power).

    The regulated 90 VDC from the 874 is crucial for autodyne detector stability (according to the manual).

    If I rebuild the power supply from scratch…

    I’m thinking 190-0-190 secondary transformer into a solid state bridge rectifier, an CLC filter (20uF, 10mH choke, 20uF)…

    What comes next is what I really need help with… I could:

    1. Put 2 massive resistors across the output for a voltage divider (180 and 90 VDC)—but that’s horribly inefficient. Plus, I don’t know if that will be enough regulation for the detector.

    2. I could just copy the output of the original power supply R-202, 203, 204, and V-203. Problem is, 874 regulator tubes are $12-$15 buck a pop, compared to VR90 regulator tubes (at $3.50 a tube)

    Could I just substitute a VR90 right into the original circuit? (and yes, I am aware the base and pin outs are different on the two tubes).

    Any other suggestions on rebuilding this power supply I’m missing or not thinking about?

    I’m all ears… er… eyes.

    Thanks in advance, and 72, Mike
     
  2. N2EY

    N2EY Premium Subscriber QRZ Page

    I would use a choke-input filter and 0B3/ VR-90 regulator. How much transformer voltage depends on drop in the rectifier and chokes used. I'd use lots of odd in the filter.

    I don't know why they put the chokes in the negative side. Perhaps to minimize insulation requirements of the chokes.

    73 de Jim, N2EY
     

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