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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

1966 deluxe reverb cuts out when volumes and treble are on 10

Discussion in 'Glowing Bottle Tube Amp Forum' started by nocastermike, May 8, 2017.

  1. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    Hey folks. i noticed today that when i dime the volume and treble the sound cuts out. I can leave it on 8.5 with no trouble and it sounds fabulous...but nudge it to 10 and it cuts out. its like it can't process anymore and just clips out. I ran the same test in 4 other various vintage fenders and they all held their own and wailed when dimed. This one however just does not like anything past 8.5 or 9 on the dial. That last little push ...and that,s it no sound. this one runs 6v6,s as you all know. The others i tested were all 6l6 models. Any ideas what this may be?
     

  2. slider313

    slider313 Tele-Holic

    Age:
    60
    916
    Jan 6, 2011
    NC
    It could be a ground issue/solder joint on the pot(s) or more likely parasitic oscillation.
     
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  3. Viejo

    Viejo Tele-Holic

    669
    Feb 12, 2011
    Southern IL
    Does the problem happen on both channels or just on the Reverb Channel? You don't state the age of the amp. but just in general it seems like lead dress got progressively worse in the CBS era. Silverfaces can benefit from cleaning up the lead dress, Not Blackfaceing but just shortening wires where possible especially grid wires. Blackface and Silverface alike can benefit from having the input leads shielded, It is an awful long run from the Reverb Channel inputs to the tube grids.
     

  4. King Fan

    King Fan Tele-Afflicted Ad Free Member

    Jan 1, 2013
    Salt Lake City
    I'm not sure it could cause your issue, but have you checked the bias? If it's a '66, have the e-caps, especially filter caps, been replaced? And way out there, I've heard of pots where the wiper no longer aligns correctly with the resistive strip...
     

  5. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    it only happens on channel 2. tried swapping out v2 and it still does it. the amp is a 1966 deluxe reverb.(original blackface).
     

  6. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    what can cause parasitic oscillation?
     

  7. charlie chitlin

    charlie chitlin Doctor of Teleocity Ad Free Member

    Age:
    55
    Mar 17, 2003
    Spring City, Pa
    It's when you have fleas or ticks in your amp...even bedbugs will do it....and they start to dance and shimmy, or "oscillate" when you play some funky rhythm...especially at high volume, as they don't hear very well.
     

  8. King Fan

    King Fan Tele-Afflicted Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Chiggers are even worse....
     

  9. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Lead dress where a grid and plate wire are too close. A dying tube can also cause oscillation.

    Once the cutting out starts can you back off the volume to 8.5 again and the amp plays normally again, or do you have to roll it lower?

    Channel 2 is the Vibrato channel and it also goes through V4B (the Normal channel does not) so the problem could be there too.
     
    slider313 likes this.

  10. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    If i back the volume back to 8.5 the problem goes away. I will try swapping out v4 tomorrow. I never usually play with volume and treble on 10. I was just killing some time today and decided to run it full out,otherwise i would have never known.
     

  11. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    Swapped out v4 today. Problem is still there. Could output tubes or the rectifier cause this?
     

  12. Piotr

    Piotr Tele-Afflicted

    Jan 5, 2011
    Poland
    How about a faulty pot?

    Anyway, with treble and volume at 10, I'd cut out too, if I stood too close to the amp, I guess.
     
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  13. crossroader

    crossroader Tele-Afflicted

    Age:
    60
    Sep 24, 2004
    Endicott, NY
    That would be the first thing I'd check.
     
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  14. ecosse

    ecosse Tele-Meister

    329
    Jul 24, 2011
    Nova Scotia, Canada
    Check the pot
     
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  15. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    Yea ...its brutal at that setting..and i never play it like that either. However something is amiss and needs fixing.
     

  16. PCollen

    PCollen Tele-Afflicted

    May 7, 2010
    Man of the World
    If it only happens on channel 2, then it's not your power amplifier section (including phase inverter).

    Do you have to have both the Ch 2 Volume and Treble on 10 for it to cut out ? Can either one be on 9- 9.5 and the other on 10 and have it function OK ? Does it just go dead, or does it "fart out" ?

    Try these first: Swap tubes V1 and V2 with each other and see if it makes a difference.

    Pull your reverb driver V3 and see if it makes a difference.

    Here is a good reference about your amp...ton's of info. If you are comfortable working on your amp when powered up, check your supply voltages at the indicated check points :

    https://robrobinette.com/How_The_AB763_Deluxe_Reverb_Works.htm
     

  17. JD0x0

    JD0x0 Friend of Leo's

    Age:
    27
    Feb 22, 2009
    New York
    What happens when you roll the guitar volume back, does it stop cutting out? Does it only happen when you hit notes/chords hard? Or the amp makes no sound when Vol + treb are dimed?

    Is it cutting out when you turn the treble from 8 to 10 or is it the volume?

    It almost sounds like you could be experiencing severe blocking distortion which can cause an amp to cut out when extreme enough
     
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  18. MilwMark

    MilwMark Poster Extraordinaire Ad Free Member

    Apr 29, 2013
    near Arnold's
    I'm just curious what caused you to try a setting that is unusable in real live (my view, anyway) and discover the issue.

    My answer is that the tone stack is so scooped at that setting, the speaker can no longer reproduce it. Or maybe it is reproducing it and is so loud, but outside the realm of human hearing, that every dog in the neighborhood weeps for the duration of your test.
     
    AlbertaGriff and nocastermike like this.

  19. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    Well..i was just attempting to see how it sounded when dimed out. My other blackface models can handle this. My super sounds extraordinary when pegged...albeit loud.
     

  20. nocastermike

    nocastermike Tele-Meister

    193
    Apr 25, 2015
    ma
    When i take the volume back..or the treble from 10 to 8. The trouble stops. Seems cranking treble plays a big part in this problem. Otherwise it sounds strong and real nice. I can crank it to 10 in the 1st channel with no problems.
     

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