5e3 static issue

Discussion in 'Amp Tech Center' started by Q tip, Nov 17, 2019.

  1. Q tip

    Q tip TDPRI Member

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    Hello everyone, old newbie here.
    I have a 2007 model Fender tweed Deluxe RI that sounds real nice but I'm getting some intermittent static. Sometimes it's louder, sometimes subtle and sometimes it's not there. Sometimes the volume drops down too.
    The amp is like new condition, tube sockets and jacks real tight.
    What I have done so far.
    -Guitar plugged in or not and volume level is irrelevant. Pulled PI tube no difference.
    -cleaned tube sockets, pots and jacks and standby switch. Jiggled everything thoroughly.
    -replaced all tubes, (though I can't remember if I tried a different rec tube and I now longer have a spare 5y3)tried different speaker.
    -chop sticked, inspected and used cold spray. No luck

    I got the service manual for this amp and checked all the voltage test points there are a few points that are out of the 20% zone specified in the manual. There is also one test point though that says to the AC voltage at pin3 of both output tubes should read 190v AC.
    I keep getting a reading of 785 and 795v AC. I don't know what I'm doing wrong to get such an odd reading.
    A little background info.
    I had the amp in to a tech who surmised it was likely a component or maybe bad connection and said it could cost a ton of money to troubleshoot so I thought I would try.
    I don't know much about electronics but know how to drain filter caps and be very careful inside amps. I have located and fixed filter cap issues in the past and worked on car electronics.
    Sorry for long post.
    Any insight would be appreciated.
    I included the schematic and with test points.
     

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  2. FenderLover

    FenderLover Friend of Leo's

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    This is a good clue that the problem is there or in the output. Did you replace the output tubes? If not, get a new pair. You'll need/want them eventually anyway.

    The PI is V2. The trouble could be there too since it is dead without a tube. Try a new V2 or swap it with V1.

    Read note 6 on the drawing - that is the signal voltage at 1KHz frequency with a specified input level. Don't worry about it until you try new output tubes.
     
    Last edited: Nov 17, 2019
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  3. Q tip

    Q tip TDPRI Member

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    Thank you for your post, I replaced all tubes with known good set a few weeks ago(can't remember if I tried rec tube long time ago as this problem has gone on for a couple years and I no longer have a spare.)
    The tech I took the amp too said that type of static could bleed into any other stages so I assume from preamp stage to output stage or vice versa and the only way may be to change components and check solder one at a time... ?
    I checked all AC voltages with a 1khz frequency (at .1 volt on my multimeter) into the mic input of the amp.
     
  4. elpico

    elpico Tele-Holic

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    If pulling the phase inverter doesn't stop the noise that pretty much rules out the preamp as a suspect. It's very likely the problem is in the power supply or power amp. You're going to need that replacement rectifier tube I'm afraid. If the new one doesn't fix it try jumpering past the standby. C10, C12, and C13 would be my next suspects as well as the resistors in the power amp (and their solder connections). D1 and D2 are longshots, but if u get this far jumper them too. Output jack, speaker cable and a different cab are more longshots
     
  5. Q tip

    Q tip TDPRI Member

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    OK. I don't think it's the rectifier tube by about 80% but it would be good to be certain about that though. I cleaned the standby but I can jumper it. Thanks a lot for all those options. I'll take one step at a time and start with a rectifier tube.
    I think I'll post my voltage test results to in case anyone is interested.
    Thanks a lot for your input.
     
  6. BigDaddy23

    BigDaddy23 Tele-Meister

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    Get the voltage chart and some pics up, mate. Can you describe the 'static' sound a bit more? Bacon frying, hiss, snap crackle pop etc?

    The volume drop is interesting - could be an intermittent ground or short problem.
     
  7. D'tar

    D'tar Friend of Leo's

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    Have you checked the speaker connections at the speaker and the jack? Not sure how these are put together. Do they have push on spade connector or are they soldered in place?
     
  8. Q tip

    Q tip TDPRI Member

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    I'm writing the voltages on a picture of the inside so it's easy to correlate the 2 should have that up later today.
    I played the amp last night and the sound didn't come on till about after about an hour give or take. It's more of a crackle pop kind of sound. I pulled the v2 again just to make sure and the sound was still there.
    I'll post those voltages and put up some pics
     
  9. Q tip

    Q tip TDPRI Member

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    Yes I cleaned the speaker jack inside the amp but to be honest it's like a brand new jack. Nice and tight and soldered solidly on the inside. It's virtually like brand new condition. I've tried different speakers and speaker cable also. I poked at all components fairly aggressively with a chopstick while amp was on and absolutely nothing.
    ****note***
    It seemed to me last night that at times when I played something that would trigger the noise. Once in the past when I went from standby to on the noise would dramatically increase so I cleaned the standby switch, which didn't seem to make any difference at the time, but it hasn't done the since. Switching from standby to on makes no audible difference now.
     
  10. BigDaddy23

    BigDaddy23 Tele-Meister

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    It sounds like an intermittent connection problem that may only manifest as it heats up. Closely check solder connections. I had a 5e3 build that did something similar (random crackles and volume drops) and it turned out to be a dodgy cathode connection to the preamp tube. Wiggling the tube is how I found it.
     
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  11. elpico

    elpico Tele-Holic

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    That moves jumpering the standby switch way up the order of things to try. That means operating/cleaning the standby switch directly affected the noise. Major clue. A standby switch is totally useless in this amp anyways, try bypassing it.
     
  12. Q tip

    Q tip TDPRI Member

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    OK so I here is a screenshot of my deluxe with voltages and where they were taken. This took me a while to do actually but I learned a bit about the preview program in my mac.
    Hope this helps.
     

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  13. elpico

    elpico Tele-Holic

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    Nothing jumps out at me there. The other thing toggling the standby does of course is charge up the filter caps. Since you've already tried new 6V6 I'd put a good bet on this being one of: rectifier tube, standby switch, C10, C12, or C13. That's a lot less than the full amp to check, should be doable.
     
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  14. Q tip

    Q tip TDPRI Member

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    Im baffled by the 780V AC readings on pin 3 of V3 and V4. I guess that's impossible but any thoughts on those readings?
    Thanks a lot by the way. This is sounding positive.
    Oh and as far as the standby switch, there are 2 wires coming from that switch and they are attached by slip on/off connectors. Would I be correct in thinking I can just slip those off and join them together you think? That would rule out that.
     
  15. Q tip

    Q tip TDPRI Member

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    I just looked at the schematic and it looks like the standby switch is just a switch so I think I can actually leave it all hooked up and bypass it without desoldering or soldering anything.
    Also, might the 2 diodes on the rectifier tube pins be causing the noise if they were compromised?
     
  16. peteb

    peteb Friend of Leo's

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    This may or may not be related to the static problem, but i would want to understand this.


    is there any AC on the plates when signal is NOT applied to the amp?


    If the 1K Hz signal on the grid, about 15 volts, is causing 785 VAC on the plate, then the gain is

    785 / 15 = 50

    a gain of 50 from a power tube is unheard of (at least to me)





    the only thing I can think of that would cause this is an unusually large plate load impedance.


    your amp works fine otherwise, so I dont think that is the case but


    what is the measured resistance of your OT primaries?
     
  17. elpico

    elpico Tele-Holic

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    Yeah the 780Vac is just a wrong number, you can tell because you have the correct AC voltage on the speaker output. Those are two ways of looking the same thing because the transformer only has one magnetic field. Measurement tools have limits, and when you approach or exceed those limits you can't trust what they say anymore. The voltage on pin 3 of the power tubes can swing very high, that's a tough signal to measure for some meters. Another point in this circuit most meters will fail to read correctly is pin 7 of V2. That's actually within 2Vdc of pin 8, but your meter is saying it's 20V off. In this game you always want to be questioning what your tools are reading, just kind of sanity checking the numbers, thinking of a way to confirm it or calibrate it or you can end up chasing ghosts. I've lost whole afternoons that way. More than once :D

    That's all correct about the standby, and yes the solid state diodes are just rainy day insurance against a catastrophic failure of the rectifier tube so they can be safely bypassed by a plain piece of wire to rule them out until you're done trouble shooting. Original 5E3s have neither of these things
     
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  18. peteb

    peteb Friend of Leo's

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    Elpico, You may be right but I am not sure. If the number was in error, I am surprised at the consistency in the numbers. These are the same numbers as the OP measured prior to post one.


     
  19. Q tip

    Q tip TDPRI Member

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    Thanks a lot for your insight on this. I look forward to trying this stuff out but I have to wait a day or so as I am way behind on some stuff right now.
    *When it comes to the diodes are your saying if I run a wire parallel to how the diodes are wired and leave the diodes on or remove them?
     
  20. Q tip

    Q tip TDPRI Member

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    It is odd to me too but when I get a chance in the next day or so I'll also measure and post the DC plate voltage as opposed to the AC voltage.
     
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