Changing Circular 3 Pin Power Plug

Discussion in 'DIY' started by Luckyorleans, Jul 16, 2017.

  1. Luckyorleans

    Luckyorleans AK Subscriber Subscriber

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    I didn't have direct contact as the sale was through a 3rd party seller, but I sent them an e-mail asking if they can check for me. There were a couple of "mystery" parts that I am pretty sure belonged with this.
     
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  2. Luckyorleans

    Luckyorleans AK Subscriber Subscriber

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    Location:
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    Unfortunately no luck in getting the external parts from the seller so it will have to go off for repair. Can't find a service manual, any ideas on finding one?

    Are requests for manual typical on AK and should I start a thread in a particular forum area?
     
  3. whoaru99

    whoaru99 Epic Member

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    Based on a little reading, it seems the PS transformer may have been undersized. Rather than repair it, per se, I'd be inclined to make an external power supply using a beefier transformer. 200-300VA, probably would be fine. I read one person estimate the original to be around 80-100VA.

    They also opined the relatively high rail voltage for the power rating of the amp was probably necessary to account for load sag, due to the small transformer (poor) regulation.

    I think fairly simple PS would be fine. Don't know if this requires +/- rails but here is probably a good starting point, if not pretty close as-is.

    http://sound.whsites.net/project04.htm
     
  4. Luckyorleans

    Luckyorleans AK Subscriber Subscriber

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    Thanks very much, I expect that this is similar to what had been done originally.
     
  5. dB happy

    dB happy New Member

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    I posted a link to a 45v 300va torroid for $36. I don't think you can get much cheaper than that. It already has a rectifier, and caps, but the caps should be upgraded to 100v. Being a redneck, I would just cut a hole in the top for the transformer if it doesn't fit, and make a vented cover for it. Maybe put a fan on it too, doesn't look like it has good cooling.
     
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  6. whoaru99

    whoaru99 Epic Member

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    It might, or not, still have the rectifier and caps. We'd need to see more pics of the OPs amp.

    Plus, I'd probably drop down 10V in the transformer if it were mine. No point, far as I know, to have 60V rails for a 60wpc amp, except to create extra waste heat. Plus, with the higher transformer VA it won't sag as much under load.
     
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  7. dB happy

    dB happy New Member

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    If it were just the main amp running on the 45v, I would agree with you about dropping the voltage. The preamp also gets it's power from the main power. Besides, everything but the caps are up to it.

    I saw the whole top of this thing is a heatsink, so cutting a hole in is out. I didn't think that aluminum box was adequate for cooling. I'd put a fan on the side where the torroid went, rig an external transformer, cut some vents in the sides, and call it good. Looks like the rectifier is still there, I think if the whole power supply was external, the wires would go to the caps or something. It would be nice to have a pic to confirm though.
     
  8. whoaru99

    whoaru99 Epic Member

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    I'd expect anything for a preamp/driver stage be regulated down anyway, to something much lower than 60V. 12, 15, 24V, maybe; something in that range.
     
    Last edited: Jul 25, 2017
  9. Luckyorleans

    Luckyorleans AK Subscriber Subscriber

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    Location:
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    Yes, the entire top is the heat sink, and the silver section was covered in heatsink paste when I took it apart. Here is a picture of the full inside and the left and right sides. Appreciate the discussion on options. I recently got a pair of Totem Rainmaker speakers and thought this amplifier would work well with it so I want to get it functional.

    DSC_3964.JPG
    DSC_3964L.jpg
    DSC_3964r.jpg
     
  10. whoaru99

    whoaru99 Epic Member

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    Based on the picture, it does appear the bridge and caps are still in place.

    But, again, were it mine if going to do the external transformer thing I'd probably take it a little further and do external DC supply, not just the trafo.

    AFAIK, it won't hurt anything to just supply external DC supply with the original caps and bridge still inside. The bridge will just add a small amount of voltage drop relative to the external supply, but in this case that's probably beneficial.

    There are a few posts/threads of the power suppy for this on other forums. I'm sure you could (maybe ready have) found them.

    Even if you went with just the external trafo, no additional DC work, it should still be better than original.
     
    Last edited: Jul 25, 2017
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  11. runnin'

    runnin' Super Member

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    Luckyorleans, how are you finding the Rainmakers? I've got a recent pair as well, and they really are a nice stand mount in my opinion.
     
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  12. Luckyorleans

    Luckyorleans AK Subscriber Subscriber

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    Sorry I just saw this. I am really enjoying them, very open and clear. They really reflect whatever your source is.
     
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  13. runnin'

    runnin' Super Member

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    I agree, very clear and open. They have a personality that monitor speakers I've had in the past do not.
     

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