j5mk1 "smoke"

    Hi,
    I've just finished my j5mk1. I switched on tha amp and smoke from OT came. The red wire soldered to lug 9 of OT is now disconnected. I could try to solder it again to lug 9. The problem is that I made a mistake. I soldered the + pole (instead of - pole) of c7 capacitor to the ground.
    Could be this the cause of smoke? Is the OT gone? What else could be it broken (capacitors, resistors)?

    Thanks to all for prompt reply.

    Nico

    Hi,

    did you swap both lugs of C7?

    C7 probably will be damaged.

    But C8 was connected correctly?

    Afaik, lug #9 isn't used for the J5:

    Lug #6 is connected to positive supply an
    lug #12 is connected to pin #7 of V3.

    But there will be other errors in the wiring.

    So check everything you did.

    Better, let someone else check it for you.

    Bernd

    Jaichweiß (Andy Pipkin)


    I didn't swap both lugs of c7. I soldered to the ground-to-earth the positive lug instead of positive lug of c7.

    Sorry,

    Zitat

    I soldered to the ground-to-earth the positive lug instead of positive lug of c7.

    but I can't understand this sentence. Could you repeat it in other words, please?

    Bernd

    Jaichweiß (Andy Pipkin)



    As you can see from plans J5mk1 rev 21c, the negative rheophores of C7/C8 capacitors have to be separately connected to the star ground point. I wrongly connected the C7 positive rheophore to the star groung point. As to OT, the model I received is ATRA0247 and I've not connected the lug 9. Owing to shortcircuit, the thin red wire of lug 9 is now disconnected.

    Hi,


    Zitat

    rheophores

    ??? ;D

    Are you using a translation program?

    Zitat

    As you can see from plans J5mk1 rev 21c, the negative rheophores of C7/C8 capacitors have to be separately connected to the star ground point.

    I've got the revisions 2.1a and 2.4. In both layouts you connect the "-"legs of C7/C8 together on the board and then you go with one (green) wire to the star ground point...


    Zitat

    As to OT, the model I received is ATRA0247 and I've not connected the lug 9. Owing to shortcircuit, the thin red wire of lug 9 is now disconnected.

    Ah, you mean the red wire which belongs to the OT itself?! That you should fix again. But be carefully. At lug #9 there is another thin wire (without insulation tube). Don't damage that by soldering the red wire.

    BTW: Did the fuse not blow up when you switched on?

    Bernd

    Jaichweiß (Andy Pipkin)


    Hi Bernd,

    I connected the - legs of C8/C7 togheter on the board. Then I connected the -leg of C8 to star ground point and + leg of C7 to star ground point. This is my mistake.The fuse didn't blow up when I switched on.

    I checked twice everything I did and it seems to be no errors except the one of + leg of C7 connected to star ground point.

    Another question. Which is the ohm value to the output plug socket?

    Thanks for your patience

    Nik

    Hi,

    Zitat

    Which is the ohm value to the output plug socket?

    I don't have this OT (Hammond 125A) in stock.

    But the DC-Resistance of the secondary output winding is in the range of 0,5 to 2 Ohms. Perhaps someone can tell exactely who has the 125A OT...

    I don't know if you connected the output jack that it makes a short if no plug is inserted...

    Bernd

    Jaichweiß (Andy Pipkin)

    Zitat von eBernd;241450

    I don't know if you connected the output jack that it makes a short if no plug is inserted...

    Bernd



    What does it mean ?

    You told me you have rev 2.4 plan. Where can i get it?

    p.s. If a jack is inserted into output socket (with no speaker connected) I get 5/6 ohm. Is it normal?

    Zitat

    What does it mean ?

    Sometimes the output jack of amps with low output power is connected in the way like input jacks. That means the switching contact (if the jack has one) makes a short between sleeve (= Ground) and tip (= Hot).
    That is done to prevent the OT from damage when running the amp with no load...

    Zitat

    You told me you have rev 2.4 plan. Where can i get it?

    I think where you bought the kit. But maybe this 2.4 Version is not public (although from Martin himself) or its just for the german version - I can't tell you...

    I don't think that there are essential changes - or have the transformers changed?

    Bernd

    Jaichweiß (Andy Pipkin)

    Hi Bernd,

    On page 21 of J5Mk1 plan rev. 21c is written that at the primary side of OT I should measure about 160 Ohm and at the secondary side (taps 2-6 as well as at the output plug socket) I should measure about 1 Ohm. Those values are to be intended for hammond 125E OT. From Musikding I received an ATRA0427 OT. Do you know the Ohm values for primary and secondary side and their taps?

    Hi,

    afaik when a ATRA0427 OT instead of the former Hammond type is delivered with a kit, then an additional sheet or manual is added which shows the differences in installation and wiring.

    Look for it - and if it is missing

    then ask Klaus by the musikding shop email to send it to you (as file).

    Bernd

    Jaichweiß (Andy Pipkin)



    Thanks Chryz

    I already got the datasheet of ATRA0427, but there is no ohm value on a single taps I'll have to find. My OT ATRA0427 tap 7 (input high voltage) I measure about 220 ohm and taps 4-15 (8 ohm output) I measure about 5 ohm. Is it normal?

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