Fender Hot Rod Deluxe Diagnostic

Discussion in 'The Projects Forum' started by Jojo_B, Jun 19, 2011.

  1. Jojo_B

    Thread Starter New Member

    Nov 17, 2009
    17
    0
    Hello,

    I've a Fender Hot Rod Deluxe 50 watt tube amp, that I've had for about ~12 years. I need someone to point me in the right direction to try to get this thing working again.

    Recently I replaced all the tubes and about 8 components because the amp was experiencing really crappy performance (very erratic sounding). After replacing all these components...the amp no longer works at all (meaning it will power up, but I can not hear anything out of the speakers when I try to use it). I believe I put all the wires and everything back into its right place.

    The specific components I replaced were all the tubes and R4, R11, R16, R22, R78, R79, R57 & R58. I replaced these because of a suggest from another website that stated that replacing these fixed the problem.

    Here's the schematic+test points/procedures:

    http://www.blueguitar.org/new/schem/fender/hotrod_deluxe.pdf

    Here are my measured test points:

    https://spreadsheets.google.com/spr...NWFzYUFXN05fMkp3WHc&hl=en_US&authkey=CI30hdoL

    You can see that nothing is working right..like I said, I wouldn't put it past me that I wired things back up wrong (since I took the whole board apart), but it's not easy to figure this out.

    Any help is appreciated, thank you.

    *edit: I have since found that Power Point Y is not reaching R58. I'm trying to figure out why this connection isn't working. R58 is one of the resistors I replaced, but it looks likes a good solder, so I'm not sure. I should also mention, all the tubes are heating up and look "on".
     
    Last edited: Jun 19, 2011
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,792
    948
    The fact that the tubes are 'on' is a good first sign that you haven't blown that portion of the amp. :)

    As for telling us things like 'as you can see', well, frankly; maybe we could help if we could, you know, like 'see'. Get me?

    If you've had a few to many on this grand old DAD's day(like me) I'm saying post us a picture or twelve.

    Edit:Nothing will test a techs metal like troubleshooting from 1600 miles away and two feet under the table, let me assure you.
     
  3. #12

    Expert

    Nov 30, 2010
    16,316
    6,818
    Note to Moderators: A Fender Hot Rod is not a car of any sort. This is not an automotive thread as forbidden in the Terms of Service.
     
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    I'd have been much more inclined to replace all of the electrolytic capacitors (frequent failure component) than a bunch of resistors (infrequent failure component).
     
  5. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    I know that the Fender Hot Rod is a guitar amplifier.
    What was the failure before you replaced the mentioned parts?
    Was there a hum?
    Was it making a cracking sound?

    Bertus
     
  6. #12

    Expert

    Nov 30, 2010
    16,316
    6,818
    No plate voltage on the phase splitter will certainly stop everything except the glow in the bottles. Good thing there's no DC coupling to the output tubes in this model.

    The worst problem here is that this is not a breakdown. It's an assembly error. Much more difficult to do from 1000 miles away because the schematic is only a "suggested" version of how the amp is hooked up. Keep adding information and you might get some good answers. More likely, you'll trace this down with your volt meter and be smacking yourself on the forehead before we get it solved from over here.

    ps, it's too young to be a Tweed. That eliminates the tar paper leakage problem...right?
     
  7. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    With so many voltages missing or far from nominal on your diagnostic spreadsheet, I'd suspect a problem with the low voltage power supply (±16V) rather than some isolated problem elsewhere.
     
  8. Jojo_B

    Thread Starter New Member

    Nov 17, 2009
    17
    0
    There is a hum when I first start it up, but I believe that is to be expected of tube amps.

    The reason I replaced the parts is that the sound was VERY crackly and the volume would saturate at a low level. (which was better than the no sound I get now).

    I've decided to do a sort of continuity check on the whole board for my screw-ups to make sure everything is connected correctly before I explore more reasons why this amp is not working.

    Here is the link I used for rationale for replacing those parts:

    http://www.justinholton.com/hotrod/plateloads.html
     
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