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total novice seeking to repair Porta-B

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    total novice seeking to repair Porta-B

    I found an abandoned Hammond Porta-B in a warehouse and I am trying to get it playing.

    It powers up and the tonewheel generators are screeching like hell, so I ordered some hammond oil on ebay.

    When I play the keys there is a very very faint sound from the speaker (volume pedal all the way up). I'm wondering if that might be a symptom of the tonewheel generator being badly in need of oil, or if there's likely some other problem (bad tubes etc). additionally, if I hold down a single key for a few seconds, it sort of fades away and doesn't sound again unless I lay off it for a while

    Does anyone have any suggestions for troubleshooting? Do these symptoms strike of any known common issues?

    I have very little experience troubleshooting electronics so I'm hoping for some general guidelines of what to look for and how to go about diagnosing the issue.

    Thanks!

    #2
    If the generator is screeching then it is turning much too slowly, so slowly that the generator notes are being filtered out by the band-pass filters on each pickup. That's why you have very faint sound. Regarding the sound that sort of fades out: it sounds like you might have percussion turned on. Don't run it any more until it's oiled and running silently! Then you can start trouble shooting; it's too early to say if you actually have a problem or not (apart from the generator sluggishness).
    Current organs: AV, BC, A-100
    Current Leslies: 22H, 142, 147, 760
    Organs in the past: L-100 (several), M-100 (x2), T-100, E-100, CV
    Other keyboards: Roland FP-4, Yamaha DX7, Yamaha TX81Z, Yamaha Motif ES Rack, Korg Krome, Novation Mininova

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      #3
      Replace the motor run cap IMMEDIATELY.
      It is toxic and prone to exploding, sending carcinogenic material everywhere
      Current:
      1971 T-202 with Carsten Meyer mods: Remove key click filters, single-trigger percussion, UM 16' drawbar volume correction. Lower Manual bass foldback.
      Korg CX3 (original 1980's analogue model).
      1967 Leslie 122 with custom inbuilt preamp on back panel for 1/4" line-level inputs, bass & treble controls. Horn diffusers intact.
      2009 Marshall 2061x HW Plexi head into Marshall 4x12 cabinet.

      Former:
      1964 C3
      196x M-102
      197x X5
      197x Leslie 825

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        #4
        http://www.captain-foldback.com/Hamm...orta_b_wir.zip Here's a link to Porta-B wiring diagrams. If you need parts, the Porta-B is basically an L-100. Clean all the tube sockets and pins, disconnect and clean all the multi pin connectors, if the tin can looking capacitor next to the run motor looks swollen, replace it before you do anything else..it is full of nasty stuff, and will squirt toxic junk everywhere if it blows up. It may take a very long time for Hammond oil to get to the bearings through the normal oiling routes...put some WD-40 in the oiing cups before you add Hammond oil to give the oil an easier path to get to the bearings.
        1963 C-3 147 Leslie
        1972 X-77GT 2 - 77P Leslie
        Kurzweil K 2000

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