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Thread: Tresham DR-102 Power amplifier with no Power Supply...HELP!!!

  1. #1
    Join Date: Feb 2016

    Location: London

    Posts: 876
    I'm Don.

    Default Tresham DR-102 Power amplifier with no Power Supply...HELP!!!

    Hi all
    Hope not breaking any rules (re: banned name) if so, Moderators please remove this post asap.

    I've come across, in my quest to find and Tresham equipment, a DR-102 power amplifier. Unfortunately it did not come with a power supply.
    I've spoken to the guy who developed these units in the 80's, (not banned name) and as far as he's concerned, all schematics went to Tannoy. He remembers certain values, but I don't want to invest in a supply that might propel the amp 20ft into the sky!

    Does anyone out there have a copy of the schematic/Component sheet + Values, so that 'll be able to resurrect this beautiful amplifier from the flames of hell? (Sorry for the Drama...) or is anyone willing to build one for me, who knows what it takes to build one?

    Distributed information system head banging required here...

    thank in advance for your thoughts.

    Regards
    Don
    Last edited by Marco; 15-11-2017 at 15:28. Reason: Banned name removed

  2. #2
    Join Date: Aug 2008

    Location: Suffolk, UK

    Posts: 1,473
    I'm Paul.

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    I am in the exactly the same position as you. I also have a DR102 but no power supply. I did strip mine down and worked out how to make a power supply, but have not got round to it yet. I can dig out the info in a few days; it's in the loft somewhere. I am 99% sure I have go it correct.

    It will take either multiple transformers or a custom wound unit, so will be quite expensive to make.
    ~Paul~

  3. #3
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

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    Judging from the photos I can see on t'web I am guessing that the power supply is just a transformer in a box.

    It doesn't help that the 'power out' and corresponding 'power in' sockets aren't marked with more info than that

    Can you take some close up pictures of the inner wiring of the power amp, it looks like there a two large reservoir capacitors in there, really need to know if the wires from the 'power in' go to a rectifier or just directly to these capacitors.

    Wouldn't be too onerous to knock up a power supply either way.


  4. #4
    Join Date: Feb 2008

    Location: Sunny (occasionally) Devon

    Posts: 1,713
    I'm Shane.

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    [Banned name] may be persona non grata round here, but he’s not hard to get in touch with. Why not email him? I promise I won’t tell anyone if you do...
    Last edited by Marco; 15-11-2017 at 15:29. Reason: Banned name removed
    Time flies like an arrow.
    Fruit flies like a banana.

  5. #5
    Join Date: Feb 2016

    Location: London

    Posts: 876
    I'm Don.

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    Quote Originally Posted by shane View Post
    [Banned name] may be persona non grata round here, but he’s not hard to get in touch with. Why not email him? I promise I won’t tell anyone if you do...
    I did as a matter of fact, and got the most negative response...
    Anyway, he was only a sales man at Tresham, Mark and Geoff were the technical guys..

    Regards

  6. #6
    Join Date: Feb 2016

    Location: London

    Posts: 876
    I'm Don.

    Default

    Quote Originally Posted by Primalsea View Post
    I am in the exactly the same position as you. I also have a DR102 but no power supply. I did strip mine down and worked out how to make a power supply, but have not got round to it yet. I can dig out the info in a few days; it's in the loft somewhere. I am 99% sure I have go it correct.

    It will take either multiple transformers or a custom wound unit, so will be quite expensive to make.
    Your right, I have the list of components, and one of them is a Toroidal hand wound jobby that costs £80

    All in, it's gonna cost £300...I have the component list, but the values are a bit vague....
    I've since made some enquiries and share the results with you...

  7. #7
    Join Date: Feb 2016

    Location: London

    Posts: 876
    I'm Don.

    Default

    Quote Originally Posted by Firebottle View Post
    Judging from the photos I can see on t'web I am guessing that the power supply is just a transformer in a box.

    It doesn't help that the 'power out' and corresponding 'power in' sockets aren't marked with more info than that

    Can you take some close up pictures of the inner wiring of the power amp, it looks like there a two large reservoir capacitors in there, really need to know if the wires from the 'power in' go to a rectifier or just directly to these capacitors.

    Wouldn't be too onerous to knock up a power supply either way.

    Hi Alan,
    The rectifiers are within the amplifier, the external box supplies power to 3 separate bridges (me thinks)..Oh yes, the previous owner decided to Burr 4 of the screws on the lid, so I'll get lid off first then take some pics...I've gotta dash now, but will post components required soon....
    Regards

  8. #8
    Join Date: Aug 2008

    Location: Suffolk, UK

    Posts: 1,473
    I'm Paul.

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    Very roughly off the top of my head so dont quote me its something like 65-0-65 AC for the low power section of the amp and 42-0-42 AC for the high current section, plus 24DC for the timer and relay circuit. I dont think there is a rectifier on the relay board, so you need one and some filter caps in the PSU for this. I think you still can get get hold of the plugs in order to make a lead up, or if not you can buy new sockets and plugs that will fit the hole in the chassis.

    Does anyone know what the rms watts into 8 ohms is? Would be a bit easier to confirm the volatges if so.
    ~Paul~

  9. #9
    Join Date: Feb 2013

    Location: Suffolk

    Posts: 1,986
    I'm guy.

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    Quote Originally Posted by Primalsea View Post
    Very roughly off the top of my head so dont quote me its something like 65-0-65 AC for the low power section of the amp and 42-0-42 AC for the high current section, plus 24DC for the timer and relay circuit. I dont think there is a rectifier on the relay board, so you need one and some filter caps in the PSU for this. I think you still can get get hold of the plugs in order to make a lead up, or if not you can buy new sockets and plugs that will fit the hole in the chassis.

    Does anyone know what the rms watts into 8 ohms is? Would be a bit easier to confirm the volatges if so.

    http://www.audioasylumtrader.com/ca/...mplifier/61863

    has some details on the power, also has the name of the founder of the company - he may be worth trying to find.

  10. #10
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    An image here of the Preamp , power supply and power amps rear panel.
    https://www.ebay.com/itm/TRESHAM-DR1...p2047675.l2557

    I think in the circumstance a letter or email to Tannoy might provide answer. A clue in the image above shows the connectors may be stocked by Radio Spares.

    Other power amps of similar vintage in the UK rarely exceeded 100w per channel, which can be achieved with 35v 0v 35v secondaries.
    Quad's 405 for instance just achieved 100w per channel into 8 ohms, whereas the Naim 250 was 80w per channel.
    My guess is there are two possibly three toroidal transformers internally in the power supply casework, nothing too fancy just laid out with fusing
    and connection to the connector block. As I say, I doubt any voltage from these exceeds 35v 0v 35v, and may include as suggested a relay designated output. A image or two internally of the power amp would assist to assist, for instance the DC specification on power supply capacitors, if they are 63v you can be fairly sure the DC rails are 50v, or slightly lower.

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