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Converting GT Brick to UK voltage

Discussion in 'Preamps / Channel Strips' started by guitarjazzman, Mar 27, 2009.

  1. guitarjazzman

    guitarjazzman Active Member

    I have just purchased a Groove Tubes Brick from the US as there is nowhere to buy one from in the UK. I was told that I can switch the voltage to 240v internally but after opening it up cannot find any obvious switches. A search on Google came up with one guy saying that I need to change some wires around. Has anyone got any ideas or a link to a guide on how to switch the voltage over?

  2. taxman

    taxman Active Member

    Contact the manufacturer.
  3. guitarjazzman

    guitarjazzman Active Member

    Tried that and am not having much luck so far!
  4. jg49

    jg49 Well-Known Member

    This might not help, I think you are stuck with GT support but if you have the unit open and trace the AC wire into the chassis there might be a small switch not usually a toggle or rocker but a slotted slide switch.

    I could not find a good pic link so I am including this

    If you enlarge this photo and look just above the plug input on the bottom right corner you will see this type of slide switch for conversion.

    Now for the bad news, when I looked up this unit many of the press releases did say internally switchable 120/240 but the most recent on the Gt site did not. Good hunting
  5. guitarjazzman

    guitarjazzman Active Member

    Cheers for that. I couldn't see a switch that looked like the one in the image. A guy at GT did email me back with an email address of a guy who might be able to convert it for me. The only thing is, he is many miles away and I was under the impression that it was quite an easy job that I could do myself. It must be a common thing to have to do so I am amazed that I cannot find any info on the net. I will keep hunting!
  6. Boswell

    Boswell Moderator Distinguished Member

    This is from one of the GT forums:
    I'm happy to do this changeover for you if you cover the (UK) carriage costs. PM me if you are interested.
  7. guitarjazzman

    guitarjazzman Active Member

    Cheers, I might have to take you up on that offer. Whereabouts are you based in the UK?
    I emailed Groove Tubes again today but am still awaiting a reply. My other option is to use a US to UK voltage converter. Not sure if that would be a good idea or not. I can't believe anyone at Sweetwater or Groove Tubes can't seem to help me out. It must be a common thing that people have done.
  8. lostindundee

    lostindundee Active Member

    Hi there

    Is an example of a (110/240v) converter this?

    If so, what is the application of these things get used?

    I'm clearly not clued up on electrics :?

  9. Williams

    Williams Guest

    The top comment on your Amazon link;
    "Does exactly what you want it to. Of course this is NOT a voltage converter, it merely changes the physical plug from US to UK. As such, the voltage on your American item needs to support the UK 240v. Please ignore the bad reviews of this product, they are from people too stupid to realize this and who plugged an American 115v product into a UK 240v socket, thus blowing fuses. This converter has no 'voltage' of its own.

    If your product doesn't support 240v then you need a voltage converter, not just a socket converter. "

    Sums it up.
  10. lostindundee

    lostindundee Active Member

    Thanks Williams

    Therefore, the first option I mentioned, the converter is what I'm looking at then.

    Thanks for clarifying this. I never noticed that there were reviews on the amazon product.


  11. guitarjazzman

    guitarjazzman Active Member

    I think I have figured out how to rewire my Brick. On the transformer, there is a list of 5 wiring pairs. The first two are identical and state 115v 50-60hz which I am quite sure are the inputs. The next three are labeled 320v, 55v and 14v (that last bit might not be quite correct as I am remembering the voltages from memory). I am thinking that the inputs to two coils in the transformer are wired in parallel (the two 115v black red-wire pairs) and need to be wired in series to make it to 230v. After many diagrams and processes of elimination, I am pretty certain that I can connect a couple of wires together to achieve my goal of plugging it into a 240v socket.

    I will be attempting my grand plan tomorrow so as long as there is no-one suddenly posting "that's wrong... don't do it!", I think I have finally solved my problem! There are also too many words such as 'think' and 'attempting' in the text above but I am feeling confident... (ish!)
  12. Boswell

    Boswell Moderator Distinguished Member

    That sounds right. It should be possible to take one black wire and one red wire and connect them together so the primaries are in series and not parallel. The trick is to find out which primary winding is which, as you don't want to end up with is one winding taking the full 240V mains input and the other short-circuited.

    A comfort check would be to disconnect the black and red wire that you think are the correct ones and measure the primary resistance with a multimeter at that point. You should get no reading (open circuit). When you connect the wire pair together, you should get a primary reading of a hundred ohms or so.
  13. guitarjazzman

    guitarjazzman Active Member

    It works! Thanks Boswell for the help, it was much appreciated. I have just put the Brick through it's paces and done some recording. Even though it was a test and the strings on my guitar are in desperate need of replacing, I was very happy with the results. An added bonus is that I now know how transformers work too!
  14. taxman

    taxman Active Member

    Transformers work on ratios of primary to secondary windings. Buy putting the two parts of the primary together in series, you doubled the ratio of input to output.
  15. keenast

    keenast Active Member

    Hi guys, would you mind and repeat the exact steps one more time....to make sure I don't fry my brick.
    Exactly which wires go now together - the two called BLK-RED and I leave all the others alone, correct?
    Also, did you (does one?) have to change the fuse, that's mounted inside the power jack?

    tx, Keenast
  16. Boswell

    Boswell Moderator Distinguished Member

    guitarjazzman will have to give you a blow-by-blow description as to what wire colours he found. And yes, you could change the fuse to one rated at half the original, but it's not essential
  17. keenast

    keenast Active Member

    tx boswell - I'll follow up with guitarjazzman!

    best, Keenast
  18. guitarjazzman

    guitarjazzman Active Member

    For some reason I am not receiving an email alert for posts or PMs... strange! I checked all my settings and even changed to a different email with no joy. Anyway, my very helpful dad has written out a description of what we did to my Brick. It was a total headache for me but hopefully the information will be helpful to anyone in the same situation. I put a page on my website with the info on at http://www.paulhill.biz/html/converting_the_groove_tubes_br.html. Please don't blame my Dad or I for any dead bricks! And yes, I did change the fuse. That was confusing too as there was a different rating stated on the unit and on the instruction sheet.

    I hope the info is of help!

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