j5mk1 - received old specification

    I received the j5MK1 kit a week or so ago. Spent a couple of nights building it. I had to google few things because they were different than documented. One thing was the power transformer which had different wiring than the one in the spec.

    Other thing was a missing 100 ohm high-power resistor. When I realized it was not included I got one from a local shop and went on with building. I just finished building the amp and started measuring if everything was fine. Obviously wasn't. I had just grounded all the pots, as specified, so the 100 ohm resistor was of no use anymore. I thought I couldn't be the only one who has realized this and googled for it. I found an answer: I had received an old version the document version (2.1c) and the current version (2.4?) does not have the before mentioned resistor anymore.

    I'm wondering if there are other things I should be aware of before I switch the amp on?

    Br,
    Henri

    Zitat von MAD;313328

    Henri,
    the only difference is the wiring of the power transformer and the ground to audio ground connection (the 100 Ohm resistor is not used any more).
    Regards,
    Martin

    That's great. Thanks for the quick reply.

    Br,
    Henri

    Hello Martin
    Just finished wiring up A15. Valves are on but no sound and input jack socket isn't 'live'. This is my first major amp project so, learning by doing.
    Have discovered that a number of the resistors I received are duff and will replace these. Photo of initial wire up available here:
    Musikding people also left out all input jacks.
    http://s1130.photobucket.com/upload/albums/B0BB0/
    When I work out how to start my own thread, will post question to forum.

    Literacy as Social Practice

    Hello Martin
    You may, of course, be right.
    I am a newbie at this and am only learning how to wire up let alone read the meter correctly!
    However, for a number of resistors, there is a discrepancy between the value in the inventory and the reading, e.g. R15 & R16 should be 470K but read 354; R28 should be 470K but reads 150; r47 should be 56K, reads 145K.
    R 17 is down as 2M2/0 now wired in, it reads .471
    While you are there, how do I do readings of the first group of resistors, those with a R value e.g. 100R/2W?
    Thanks for your help and advice.
    Robert

    Literacy as Social Practice

    In fact, I think you are right, having replaced one resistor and measuring it off the board, the value changed.
    I will have to check the rest of the wiring.
    Will post photos and ask for suggestions.
    Robert

    Literacy as Social Practice

    Robert,
    I'n not sure to understand your problems with the resistors, but If you want to measure the values of the resistors shown in the schematic while the resistor is already assembled you will fail for most of the resistors! The values shown for all parts (R and C) in the schematic are only valid for the respective part being measured separately not in the circuit!
    I don't want to upset you, but are you sure building a tube amp of this complexity with lethal voltages it appropriate for you? I propose to look at least for a knowledgeable person to support you, otherwise you might be frustrated with this kit and - allow me to state it again - a tube amp runs with lethal voltages!
    Regards,
    Martin

    Yes.
    Thanks for this.
    What can I say? I've got the kit. I've used your instruction manual.
    I've put the kit together. I'm trouble-shooting.
    I'm looking to get it working.
    Regards
    Robert

    Literacy as Social Practice

    Hello again Martin
    It's working well now thank you.
    One of the shielded cables was badly soldered so the signal was getting lost.
    By the way, if you can send me a non pdf version of the English manual, I can improve it for you.
    I am a teacher educator and English is my specialism.
    My email is rob.smith@wlv.ac.uk
    Regards
    Robert

    Literacy as Social Practice

    Zitat von MAD;313760

    Robert,
    thanks for your offer, I will contact you (I'm just planning to review and update some manuals anyway).
    Regards,
    Martin




    Whenever you're ready
    best wishes
    Rob

    Literacy as Social Practice

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