GT"The Brick"; how to change primary voltage switc

Discussion in 'Preamps / Channel Strips' started by Resurrected, Jan 15, 2006.

  1. Resurrected

    Resurrected Guest

    Hi there,

    just ordered "The brick" from the US. Now I need to change the internal voltage switching from 110V to 230V as I live in Germany. I just had a look inside the unit but I cannot find any switch for my purpose.

    Any help ?

    Regards,

    Resurrected
     
  2. Kev

    Kev Well-Known Member

    Joined:
    Nov 13, 2001
    IF the power transformer has dual primaries then it may be possible to re-configure the input




    sorry I just can't see enough detail to be sure
    you need a tech to look inside for your

    please be careful of the 220 / 230 mains power

    There was a thread here with better inside pictures but I can't find it right now
    :oops:
     
  3. Grooveteer

    Grooveteer Guest

    Here's the thread Kev is referring to: (I think)


    (Dead Link Removed)

    Hope this helps.
     
  4. Resurrected

    Resurrected Guest

    Voltage switch

    Thanks for your posts !!! As our bassplayer is a great tech engineer I'll ask him to do it. What I do not understand is why Groove Tubes claims that Pirmary Voltage is switchable inside; it's not that easy I think as there's no real switch at all...

    I'll tell you if I proceed...

    Regards,

    Resurrected
     
  5. Grooveteer

    Grooveteer Guest

    Why don't you ask Groove Tubes? Last time I had a question Sam Austin was very helpful. You can reach him at proaudio AT groovetubes DOT com

    Good luck!
     
  6. Resurrected

    Resurrected Guest

    ...have asked Groove Tubes last week already

    I've asked GT last week but didn't receive any answer 'til yesterday. They've got the solution, here's their statement:

    "Find the two inside wires (RED, BLACK) off the power transformer
    follow them up to the power switch and cut them off at the power switch
    being carefull not to cut the other black and red wires.
    Now strip and twist them together.
    Also insulate.

    Done.... now you have just converted it from 120v to 230volts"

    Will check this out today & inform ya on the result...[/code]
     
  7. Kev

    Kev Well-Known Member

    Joined:
    Nov 13, 2001
    As I said
    dual primaries

    parallel for 110 volts
    series for 220 volts

    joining the (RED, BLACK) puts the primaries in series
    8)

    it's all good
     
  8. robbi

    robbi Active Member

    Joined:
    Wednesday
    Location:
    UK
    Hello,

    I have tried to convert the Brick I have from 115v to 230v using this method, however, blowing fuses (250mA, as per the back of the unit). It's entirely possible that I've messed up the conversion some how--do you have any pictures of how you did it?

    Here is how I did it:

    https://drive.google.com/open?id=1au...11jaLOYa08r6Ze

    (please excuse crappy job).

    These are the "top" pair of red and black from the transformer.

    Another view of the top of the xformer:

    https://drive.google.com/open?id=15Q...y1-jC7pSsJ57Hj

    Any help is appreciated!

    Many thanks,
     
  9. Boswell

    Boswell Moderator Distinguished Member

    Joined:
    Apr 19, 2006
    Location:
    UK
    Home Page:
    The 2006 post that quoted the GT instructions said find the inside red and black wires at the transformer and cut these two off the switch, then join the free ends together. Your first photo shows two wires taped together, but there are other wires in the photo, so it's hard to tell for certain whether the taped pair are a red and a black. They are presumably wires that used to go to different sets of contacts on the switch. Please confirm.

    I take it that GT meant that the two 120V mains windings are wound layered on top of one another, and that the modification effectively creates a single continuous 240V winding. If so, you would get the order from outside inwards (or vv) red-black-red-black, so by "inside" they mean "middle". What they don't say is whether red and black sleeving has been put on each winding to denote the start and finish (normal) or whether there is a winding with red sleeves and another with black sleeves (crazy).

    I would hope and expect that each winding has a red and a black sleeve. The easiest way to check this is to disconnect the mains and temporarily undo your join. Measure continuity using a battery-powerd Ohm-meter of each red-black pair, where you should find that a winding will be something like 20 Ohms. There should be no continuity shown from one winding to the other with your join un-made.
     
    Kurt Foster likes this.
  10. robbi

    robbi Active Member

    Joined:
    Wednesday
    Location:
    UK
    Thanks for the input, Boswell; it's done the trick, the penny dropped when you brought up "inside", I had originally done the top pair of red and black. Unit is functioning correctly on 230v!

    Many thanks,
     
  11. Boswell

    Boswell Moderator Distinguished Member

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    Location:
    UK
    Home Page:
    Well done! Glad it works now.
     
  12. robbi

    robbi Active Member

    Joined:
    Wednesday
    Location:
    UK
    Yes, thanks for the help with it.

    I have a different issue with it, sonically; it sounds very thin and lacking bass, neutered, compared to a Focusrite Trakmaster. I have swapped the 12AX7, waiting on a 12AU7 to be delivered to check it.

    Is there any thing else I might be missing if the tube swap doesn't help? Maybe time to take to a tech...

    Many thanks,
     
  13. Boswell

    Boswell Moderator Distinguished Member

    Joined:
    Apr 19, 2006
    Location:
    UK
    Home Page:
    OK, a few questions: Is this "thin" sound heard when you are using the microphone input or the DI? If microphone, what model of microphone, and what's the sound source? What are you feeding the output of The Brick into? What type of cabling are you using at the input and output of The Brick?

    The reason for all this probing is that it is technically possible that your connecting 240V to a 120V mains winding on the transformer caused some over-stressing of internal components for the few tens of milliseconds before the fuse blew. This is not very likely, but it would be good to eliminate external effects first.
     
  14. robbi

    robbi Active Member

    Joined:
    Wednesday
    Location:
    UK
    It's both the instrument input and the mic input that are sounding this way. I've fed the mic input with a speaker simulator (XLR -> XLR) coming from my amp/attenuator, and then the DI with guitar (TR instrument cable), and an iMPC app, from my phone. I am sending all these signals into a Tascam 388, which was leaving the Brick with an XLR -> TRS cable into the line input of the mixer. All of these signals sound thin, especially in comparison to the Trackmaster, hooked up and used in similar ways to the Brick.

    Many thanks,
     
  15. robbi

    robbi Active Member

    Joined:
    Wednesday
    Location:
    UK
    I've tried it as an insert aswell now--same thin sound. Would be good for a lo-fi effect!
     
  16. Boswell

    Boswell Moderator Distinguished Member

    Joined:
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    Location:
    UK
    Home Page:
    Well, that's interesting information. I would have said the input transformer was a suspect for this effect, but since the DI input does not go through the transformer or the first valve stage, that's ruled out.

    The only repair work I've done on a Brick that had similar symptoms to those you describe was to de-gauss an input transformer. This was after an intermittent XLR cable short when phantom power was applied caused core magnetisation. However, in that case there was evident distortion at higher amplitudes, which you haven't mentioned.

    How confident do you feel about prodding around inside the Brick with a multimeter and (possibly) an oscilloscope? I must warn you that there are some lethal voltages in there.
     

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