Blues jr mod disaster - help needed! :P

Discussion in 'Amp Tech Center' started by cobraclutch, Nov 20, 2019.

  1. cobraclutch

    cobraclutch TDPRI Member

    Age:
    39
    Posts:
    6
    Joined:
    Nov 20, 2019
    Location:
    Australia
    Hey guys,

    I know I’m just a new member, but would appreciate any help for a damn old fool! ;)


    I recently purchased a Fromel Complete mod kit for my BJ.

    I have a Blue Junior III 2010 (REVISION D I assume) and decided to install a Fromel kit, but have stuffed something!


    It powers on fine, light comes on, but I can’t get anything from the guitar.

    There is a slight stable hum that is a bit louder than before, which ramps up with the volume (gain), not the master.

    And also changes pitch with the treble, which it did do at high volumes before also, if you paid attention while not playing.

    There is also a pitch change when you touch the guitar input, or put the jack in, which used to be silent.


    In fact the whole amp was very quiet until I threw a spanner in the works.


    The tubes fire up and everything, but just no signal.

    No smoke from anything.


    The original large capacitor always read 6 volts after it self-discharged, and the new one read exactly the same.

    It’s the only thing I put in that is polarized (apart from the jack).


    I did accidentally lift the pad on the PCB when installing the new WIMA cap on the bass pot (C6), but I scratched back the lead and it seemed to solder on okay, that’s only thing I can think of that didn’t go as planned (or so I thought).

    To be fair, I’ve never seen a pad lift so fast.


    I’m no tech, but I live out in the sticks in Australia, so there was no real option but for me to do it myself.

    I did start an electronics degree when I was young and both my brother and father are electronic engineers, so I thought I would still retain some of the skills I had, but maybe not!

    First time I’d even used a multimeter for a long while.


    How can I problem solve this thing to track down the problem?


    I know it’s hard without the amp in front of you, but if you could give me some easy rookie tips, that would be great.


    The only vague instructions were with the input jack, so maybe I screwed that, but not sure how.



    I did the Fromel Complete for MIM (made in Mexico) set, which is:

    Replaced C25 main filter electrolytic cap with 100uF/450v.

    Replaced C5 with a 250pf Silver Mica

    Replaced C6 + C7 with .1uF + .015uF WIMA caps respectively.

    Put a jumper on the mid pot.

    Replaced bias resistor with a 33k at R52

    Installed new input jack, not mounted to the board.

    I disconnected the trans leads and dressed them better and replaced them.

    This is the kit:

    https://fromelelectronics.com/collections/amp-mod-kits/products/bjr-mods?variant=776492411



    [​IMG]


    Note: The white resistor is just to discharge caps.

    And I didn’t put the extra little cap in (disable ‘sparkle mod’)


    Here’s the schematic:

    https://www.thetubestore.com/lib/th...r/Fender-Blues-Junior-III-Schematic-Rev-D.pdf




    Anyway, thanks for your time...

    :?
     
  2. Deebs3

    Deebs3 Tele-Meister

    Age:
    53
    Posts:
    164
    Joined:
    Sep 1, 2018
    Location:
    Australia
    Maybe check speaker is connected properly? Other wise I got nothing.
     
  3. AndyPanda

    AndyPanda Tele-Meister

    Age:
    65
    Posts:
    256
    Joined:
    Sep 4, 2019
    Location:
    Bay Area, California
    Are you sure you got the new input jack wired correctly? If you wired it backwards (grounding the input signal) that would explain why you don't get any sound.
     
    D'tar likes this.
  4. cobraclutch

    cobraclutch TDPRI Member

    Age:
    39
    Posts:
    6
    Joined:
    Nov 20, 2019
    Location:
    Australia
    I have been thinking the whole time it is something with that jack, so I hope it is, will have to check when I get home.
     
  5. Milspec

    Milspec Friend of Leo's

    Posts:
    4,073
    Joined:
    Feb 15, 2016
    Location:
    Nebraska
    Plugged into the right jack...not trying to be insulting, but they do have a extension socket as well. If you plugged into that socket, you would get exactly as you described. Sometimes the simple things happen, we are all human.
     
  6. cobraclutch

    cobraclutch TDPRI Member

    Age:
    39
    Posts:
    6
    Joined:
    Nov 20, 2019
    Location:
    Australia
    Not insulted at all! I'm the idiot that did this. :D
    There isn't an extension port, but there is a pedal port next to the speaker port, but no it was the first thing i checked.
    I wished it was that!
     
    Milspec and bcorig like this.
  7. bcorig

    bcorig Tele-Afflicted Silver Supporter

    Posts:
    1,578
    Joined:
    Mar 11, 2018
    Location:
    Chino Hills CA
    Let’s start with “you are not an idiot”.
     
  8. cobraclutch

    cobraclutch TDPRI Member

    Age:
    39
    Posts:
    6
    Joined:
    Nov 20, 2019
    Location:
    Australia
    Can I get that on a feel good poster???
     
    Whatizitman and bcorig like this.
  9. graybeard65

    graybeard65 Tele-Meister

    Age:
    54
    Posts:
    118
    Joined:
    Jun 30, 2016
    Location:
    Rochester, MN
    If you do get it on a feel good poster, chances are that it would be written "your not an idiot." - and I'd want one too!

    Kudos to you for working on your own amp - I'm not brave enough myself - I hope that it all works out!
     
    bcorig and DonM like this.
  10. JMac52

    JMac52 Tele-Meister

    Age:
    58
    Posts:
    131
    Joined:
    Apr 26, 2018
    Location:
    Mesa, AZ
    Check the ribbon cable connections at the main board and the tube board, in particular the outermost wires of each ribbon. It’s easy to work those loose of their solder connections when you pull the board out and put it back in. I speak from experience...
     
  11. cobraclutch

    cobraclutch TDPRI Member

    Age:
    39
    Posts:
    6
    Joined:
    Nov 20, 2019
    Location:
    Australia
    Yes, and the instructions called to reshape them to take any kinks out, which I thought might cause breakages, but did it anyway, as I thought, what would I know?
     
  12. Pasta Player

    Pasta Player Tele-Meister Ad Free Member

    Posts:
    140
    Joined:
    Feb 5, 2019
    Location:
    Middle America
    Check for continuity / resistance on everything you installed / replaced. I have woefully installed bits (without first checking them) and reassembled everything and always suspect that it is something that I have done incorrectly… only too often find afterwards, that there were simply bad items supplied. (Recently a bad, non-functioning new 10K pot.)

    AND tube sockets on the BJs are pretty fragile, check all those solder points too.

    You will figure it out.:twisted:
     
  13. bcorig

    bcorig Tele-Afflicted Silver Supporter

    Posts:
    1,578
    Joined:
    Mar 11, 2018
    Location:
    Chino Hills CA
    Yup.
     
  14. cobraclutch

    cobraclutch TDPRI Member

    Age:
    39
    Posts:
    6
    Joined:
    Nov 20, 2019
    Location:
    Australia
    Got dat sommabitch!

    input grounding on wrong hole as it changed with the new one - oops!

    cheers, you are all powerful and attractive men!
     
    Veltek and Whatizitman like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.