Slight hum from reverb channel Deluxe Reverb silver face

Discussion in 'Amp Tech Center' started by Rockinvet, Oct 28, 2019.

  1. Rockinvet

    Rockinvet TDPRI Member

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    I have a slight hum from the reverb in my Deluxe reverb. Pulled V3 and V5 to see if it was the tubes but no such luck. It’s not a real buzz or bad hum it’s just there when I use the reverb and when mic’d up it is annoying. Another characteristic is that when I turn the reverb down or up it adjusts linearly with the pot. Go to zero it goes away, go to 10 it’s loud (never play at that just testing). This is with or without vibrato channel tubes. So, I assume something else is wrong. Tha amp is a 76 DRSF and it sounds awesome otherwise. Any suggestions?
     
  2. rolandson

    rolandson Tele-Meister

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    You pulled V3 and 5, what about switching out V4? Half of it is your reverb recovery...

    No joy there, trace the tank leads for issues.
    Inspect the tank.
    If within your skill set, pull the chassis and inspect with a chopstick, starting with the RCA jacks and tapping each component in the circuit.

    I found a failed resistor in a 763 reverb circuit that way.

    Or...time for a visit with a good tech.
     
  3. schmee

    schmee Poster Extraordinaire

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    The reverb on BF/SF amps hums when you turn it up. It should be pretty quiet at 3-4 but can be annoying at 5-6 or more. The pot is also pretty front loaded... ie: Jumps to on at 2+ and by 3+ a lot of reverb.
    There is a mod to spread the adjustment of 1-5 over the 1-10 dial for smoother adjustment.
    But Fender spent years trying to quiet the reverb channel. Added caps, added spiral wiring around some of the wire routing etc.
     
  4. Rockinvet

    Rockinvet TDPRI Member

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    Will check v4 next. Thanks. After that it’s on to chopstick. Will let you know how it goes.
     
  5. rolandson

    rolandson Tele-Meister

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    The resistor I discovered appeared normal visually, such that I passed on in my inspection...but when I came back at it with the tapping, it crumbled.
     
  6. homesick345

    homesick345 Poster Extraordinaire

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    Nope. Not in my experience with many bf/sf amps. Reverb is almost dead quiet all the way up. Humming at 5 is not normal at all
     
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  7. schmee

    schmee Poster Extraordinaire

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    Well, I've only had those amps for 55 years so I guess I'll get one like yours eventually! Maybe Lebanon has clean power!
     
  8. homesick345

    homesick345 Poster Extraordinaire

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    I had those amps for as long as you, and bought them/played them in Canada and US. Don't assume anything.

    A fender reverb humming / hissing at 5 is not normal, and should/could be fixed.
     
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  9. rolandson

    rolandson Tele-Meister

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    My experience as well. My pair of 52 year old blackfaces are, when in proper working order and fed a diet of clean electricity, quiet as church mice.
     
  10. Rockinvet

    Rockinvet TDPRI Member

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    Problem solved. It was a reverb tank connection issue. Which I would have never guessed having pulled v3 and v4. Next time I will trouble shoot more before I ask a question.
    Thank you for your recommendations.
     
    King Fan, Wally, schmee and 2 others like this.
  11. BobbyZ

    BobbyZ Doctor of Teleocity

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    Good ground connection on the shield cable will cause noise, as you found. Serviced a BFDR once, all was well on the bench with a bench reverb pan. Put it back in the chassis and got the local AM radio station, along with some static. Bad solder joint where the shield goes on the RCA plug. Amp had worked for years like that I suppose it slid back a bit when I pulled it apart. Slid it back tight and the problem went away. Think I soldered it?
    On an old Ampeg if that happens you'll get a squeal like you wouldn't believe! A 12ish watt Reverberocket makes about the same volume sequel as standing in front of a 100 watt Marshall with a hollow body.
    Well maybe the Marshall's a bit louder but not by much. :)
     
  12. King Fan

    King Fan Friend of Leo's

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    Nice. Ya gotta like a guy who accepts advice, tries the ideas suggested, understands what they mean, and reports back -- with appreciation. Wish we could put that in an aerosol and spray it on some other help threads...


    Good one, Bobby. When you 'round up the usual suspects' and there's an RCA plug in there, you can usually send the other suspects home.
     
    BobbyZ likes this.
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