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Thread: Need PYRAMID PS-25 Schematic

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  1. #1
    Join Date
    Oct 2008
    Location
    Roseville, Ca.
    Posts
    1

    Exclamation Need PYRAMID PS-25 Schematic

    I am looking for the electronic schematic
    for a PYRAMID PHASE-III Model: PS-25
    Power Supply.

    Any help would be greatly appreciated.

    Thanks,

    Beau Palmer
    WB6YYS
    bpalmer@surewest.net

  2. #2
    Join Date
    Jan 2000
    Location
    South Central Alabama
    Posts
    2,266

    Default PS-25 schematic

    Beau,
    I sent You an Email with a schematic for the PS-35 ....Hopefully it will be close enough to help.

    OK, I'll post the schematic ....guess I never thought that others would need also.
    http://userpages.troycable.net/~wj5o/PS-35.jpg
    It just takes me a little time to get this on my ISP...... Hope others that need it will also see this post.
    Last edited by WJ5O; 10-27-2008 at 08:34 PM. Reason: adding schematic to the response.
    73 Bill WJ5O/BCN 28.289 MHz

  3. #3
    Join Date
    Nov 2004
    Location
    Donalsonville Ga
    Posts
    979

    Default

    WJ5O

    Well it sure would be nice if you could post the schematic on here. I have a Phase III Ps 25 also that ain't working.
    73's


    Bill W4BD
    Donalsonville, Ga.

    EX W4BPK
    SPAR # 529
    Member ARRL
    FELD HELL GROUP #FH2357

    IF IT'S POLITICALLY CORRECT THEN IT'S A LIE

    THE ONLY GOOD GUN CONTROL IS HITTING WHAT YOU ARE AIMING AT

    I DO EQSL OR DIRECT OR NO QSL DUE TO THE FACT THAT I CHASE NO AWARDS

  4. #4

    Post

    Beau -

    The Pyramid company of the Phase III era no longer focuses on the low-end CB radio / car audio market.
    The Pyramid Car Audio company focuses on the car audio, guitar amp and audiophile -- larger market that spends more $$.
    http://www.pyramidcaraudio.com/items...+%2F+Inverters

    The Phase III design (1970s/1980s) used the LM723 IC regulator with 2N3055/2N3771 NPN pass transistors.
    To learn more about linear power supplies that use the LM723, see the Repeater Builders web site (Astron web page).
    http://www.repeater-builder.com/astr...ron-index.html

    The Phase III design suffered from an undersized heat sink -- so I recommend adding a 80 cm computer fan (12 VDC) on these heat sinks.
    The electrolytic capacitors used by Pyramid were 25 VDC units --- and overall capacitance is usually too low.
    I usually select 35 VDC units and use 1,500 to 2,000 uF per AMP output.
    So a 20 amp supply should have 30K to 40K uF for the DC capacitors.

    w9gb
    Last edited by W9GB; 10-27-2008 at 10:40 PM.

  5. #5

    Default

    I had one of those Pyramid Phase 3 PS-25 power supplys in the early 80's, and used it for about 10 years. The only problem I ever had with it was the rectifier shorted one morning when I turned it on. I replaced the rectifiers with a generic ECG 40A, 800V PIV bridge. Never had a failure with it again.

    One thing I noticed was the PS-25 was quite imune to RFI on VHF, but had very bad RFI at HF. Running 100 W on HF would cause the voltage regulation to go nuts. I fixed that problem by installing three .1 uF/600V capacitors on the output terminals- one from PLUG to GROUND, one from MINUS to GROUND, and one from PLUS to MINUS. Solved the HF RFI issue.

    Tom, KA1MDA
    www.ka1mda.org

  6. #6
    Join Date
    Jul 2007
    Location
    Toledo, OH
    Posts
    6

    Default

    I just inherited a Pyramid Phase III 35 Amp Power supply. Does anyone have a user's manul for it? It seems to work fine, but I would like to know what the buttons are supposed to do.

  7. #7
    Join Date
    Jan 2000
    Location
    South Central Alabama
    Posts
    2,266

    Default I'll look for manual

    Well, I have the schematic so I must have the 1 or 2 page operations manual somewhere on the premises....... I'll take a look under the bench......

    I GOT IT...on the way to KA9IVY via QRZ listed Email
    Last edited by WJ5O; 01-27-2009 at 09:39 PM. Reason: to add "I GOT IT"...add KA9IVY for clearity
    73 Bill WJ5O/BCN 28.289 MHz

  8. #8

    Post

    QST magazine has articles on repairing linear power supplies of the
    LM723 IC regulator and 2N3055/2N3771 NPN pass transistor design ..
    December 2005 QST issue
    http://www.repeater-builder.com/astr...y-analysis.pdf

    Repeater Builders -- under their Astron category.
    You will find that the Pyramid Phase III was an attempt to produce a Far East copy
    of the Astron models (most failed in quality of assembly and parts selection).
    Place an Astron schematic side-by-side with the Pyramid -- The LM723 design has been fairly standard since 1970s
    http://www.repeater-builder.com/astr...ron-index.html

    David Metz's Classic article on linear DC power supplies
    http://www.repeater-builder.com/astr...on-article.pdf

    w9gb

  9. #9
    Join Date
    Jul 2007
    Location
    Toledo, OH
    Posts
    6

    Default

    Bill, Thanks so much for the manual. It is just what I needed.
    Richard, KA9IVY
    [email]ka9ivy@arrl.net[/email]

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