Need help; 5F1 build completely dead.

Discussion in 'Shock Brother's DIY Amps' started by teek_s, Sep 21, 2020.

  1. teek_s

    teek_s TDPRI Member

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    Hello everybody! I'll preface this by saying that I'm a first time builder, and I have no experience building amps. I've been lurking around here with no account for quite a while now, but with this most recent issue I thought I should finally make an account and ask for some help. I've had a massive interest in building amps for quite a while now, and with the start of our quarantine a few months back, I thought it was finally time to get around to it. It may be important to note that I am not using any sort of kit for this build; the components were bought over the span of a few months in small orders. To start, I finally completed my very first 5F1 build two days ago, and I've had no luck troubleshooting with the resources I've found already. My issue is, whenever the amp is plugged in and the on switch is flipped, absolutely nothing happens. The indicator light stays off, the tubes never come to life, no sound is outputted, and even doing the deadly and poking around the amp while plugged in, no current whatsoever is outputted from the power transformer. I am sure the wiring is correct, as I have poked in there with a multi-meter and found all the expected results. The fuse isn't dead, and the indicator light bulb isn't broken or burnt out. To give more info, I am using the Classictone 5F1 PT. I believe it is wired correctly, as the hot from the power cord is ran through the on-off switch to the first black lead, and the neutral is connected to the second black lead. The amp has been grounded to earth with the green wire. I have included a few images of the amps guts, please pardon the messy wiring. Thanks a million for the help!

    IMG_20200921_115329.jpg IMG_20200921_115336.jpg IMG_20200921_115345.jpg
     
  2. awasson

    awasson Poster Extraordinaire Gold Supporter

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    Well, I’m sure some of the old guard will pipe up with useful troubleshooting information but the first thing I would do is turn it off and unplug the AC from the amp. Then I’d drain the capacitors and test them to make sure they are drained.

    It sounds like the heater circuit isn’t working to me but the power supply is the heart of the amp so it needs to be right.

    pull the tubes put them somewhere safe and disconnect the secondary windings of the power supply from the circuit to make sure that you have the power supply wired right. I would only have the primaries connected, through a fuse and switch. The secondaries would be safely removed from everything so I could ensure that I was seeing the correct voltages.

    Once you know you have the correct voltages on the windings, you can look at the rest of the circuit.
     
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  3. Diverted

    Diverted Tele-Meister

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    If you're getting no power at all, start with checking the health of the varioius windings and coils, with the amp unplugged.
    Verify there is continuity across the fuse jack leads.
    Check from pin 4 rectifier to ground.
    Check from pin 6 rectifier to ground.
    Check for continuity on primary on power transformer (black wires).
    Check output transformer primary for resistance by measuring from pin 3 6V6 to output of rectifier/first filter cap positive.
    Check for output transformer secondary for resistance
    Check 5v winding resistance by measuring between pins 2 and 8, rectifier
    Check 6V winding resistance by measuring from pins 4/5 and 9 on the 12AX7. This is the last tube in the heater string so it's the most convenient place to check. Also check at the 6V winding's first tie-off point; likely the pilot light.

    This is just a first step. If you get good readings here you can tentatively look elsewhere and try voltage readings with amp under power. But if not, you can isolate the problem pretty quickly if you aren't getting what you should be getting.
     
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  4. mjcyates

    mjcyates Tele-Meister

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    Hard to tell exactly what's going on from your pictures. If you build it exactly like Rob's layout you won't have any problems. 5F1_Champ_Layout (2).png
     
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  5. awasson

    awasson Poster Extraordinaire Gold Supporter

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    Hold the bus...

    this is completely wrong and dangerous. The green wire in this photo needs to be grounded with a bolt and star washer. The white wire needs to be insulated.

    [​IMG]

    I would recommend after figuring out your power sources as I suggested above, rewiring your power supply so that it’s safe.
     
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  6. tubegeek

    tubegeek Friend of Leo's

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    Step one in this case has to be, to verify your power transformer - this is very likely to be your problem given your description.

    Two basic possibilities: open circuits (no connection where there should be one) or short circuits (a connection where there should be none.)
     
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  7. awasson

    awasson Poster Extraordinaire Gold Supporter

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    From the photo I posted, it doesn’t look to me like the AC is entering the power supply primaries... the white wire off the fuse connector looks like it’s entering the capacitor bank?

    On a deeper look, it appears that it could be ok. It looks like ac power enters the fuse, goes to the switch and then into the primary.

    Again, that power supply needs to be cleaned up, made safe and then, and only then would I look at what else is going on.
     
    Last edited: Sep 21, 2020
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  8. Peegoo

    Peegoo Friend of Leo's

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    Is there a fuse in the fuse holder? if so, use a meter to test the fuse.

    Meter the continuity of the power cable from the plug prongs to the solder connections for all three conductors in the cable (live, neutral, ground).

    Meter across the power switch to ensure the switch can pass current.



    Note: the ground wire from the AC mains cable jammed behind the nut on the fuse holder is...janky and dangerous. Reroute that green wire to the chassis ground stud in the left side of your first pic.

    Despite that, all your soldering looks very good!
     
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  9. teek_s

    teek_s TDPRI Member

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    Thank you all very much for the quick replies. There is a fuse in the fuse holder and it has been tested. I've checked all the connections from the power chord and the switch can pass current. I'll definitely get on rewiring the ground with what was recommended. As for what Diverted has recommended, I'll get on that ASAP as well. Again, thanks for all the quick responses, and I'll give updates as soon as I can!
     
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  10. tubegeek

    tubegeek Friend of Leo's

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    With the amp unplugged, and the switch in the "on" position, you should be able to measure a small resistance - but not 0, and not open - between the two blades of your power plug. That will indicate that the primary is connected to the wall when the switch is ON and the plug is in.

    Have you built a light bulb limiter?

    And just to be clear - the transformer is Classictone 40-18019 and it has ONLY two black primary wires - it's not an export transformer with 120V and 240V options?
    40-18019.jpg
     
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  11. Nickfl

    Nickfl Friend of Leo's

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    Do you have a lightbulb limiter?
     
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  12. teek_s

    teek_s TDPRI Member

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    I don't have a lightbulb limiter. Would that tool be useful for troubleshooting?
     
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  13. teek_s

    teek_s TDPRI Member

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    Also as a quick update, the green wire has been secured with a star washer and soldered to ensure a proper electrical connection as well as mechanical. And yes, the transformer is a Classictone 40-18019.
     
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  14. tubegeek

    tubegeek Friend of Leo's

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    Quite.
     
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  15. tubegeek

    tubegeek Friend of Leo's

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    So, next test: do you read less than 2 ohms from the ground pin on your power cord to your chassis, pick a spot, any spot. (Also: power CORD not power CHORD!)
     
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  16. teek_s

    teek_s TDPRI Member

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    I'll do some research on it. Thanks!

    Sorry about the typo, it's my inner musician getting to me, lol.
     
  17. Peegoo

    Peegoo Friend of Leo's

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    The green/yellow wire on the left in your first pic: is that running from the lamp holder to ground?

    If it is, that's incorrect and is draining your lamp and heater voltage to ground.



    @awasson Sorry! I didn't see your comment on the AC mains ground lead.
     
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  18. tubegeek

    tubegeek Friend of Leo's

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    Ideally, you'd have a light bulb limiter for the next test.

    What you will want to do is remove all your tubes, and WITHOUT POWERING UP test to see whether any of your secondary windings are shortcircuited. This is something that you MAY be able to tell just by listening for a humming sound when you plug in, or whether the fuse blows. The safest way to do it is to have a light bulb in series with the "hot" connection in your power circuit (so, between the wall outlet and the "hot" blade of the power cord) and this will give you a visual indication of whether the power supply is drawing a lot of current into a short circuit. A normal amp draws less than 1 A of current after settling down, which a 75 or 100W light bulb will pass without even lighting up very brightly - this is what you are looking for.
     
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  19. teek_s

    teek_s TDPRI Member

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    The green/yellow wire is the center tap from the PT, and it is running to ground. Should it not be?
     
  20. Peegoo

    Peegoo Friend of Leo's

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    You have that wired correctly. It was hard to see in the pic. Thanks!
     
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