NAD 1966 Blackface Band-Master

Discussion in 'Amp Central Station' started by HD28, Sep 15, 2021.

  1. HD28

    HD28 Tele-Meister

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    Just got this time machine. Came from a Canadian rock and roll band guitar player of some renown. I don’t know why he sold it. I don’t care. No one has been under the hood of this machine. It’s in marvellous shape.
    Please take a look. AB763.
    The tremolo bug does not have its sleeping bag, but a layer of very old slimy 88 tape. @Wally, can you chime in on this?
    Thanks
     

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    Last edited: Sep 15, 2021
  2. Crobbins

    Crobbins Friend of Leo's Silver Supporter

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    Nice score. congrats.
     
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  3. Terickson

    Terickson TDPRI Member Silver Supporter

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    Nice amp! Folks would sometimes cut the trem roach cover off to see if it worked.
     
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  4. HD28

    HD28 Tele-Meister

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    That's unfortunate.
    I have to put a dark blanket on him now...
     
  5. Dana Rudd

    Dana Rudd Tele-Afflicted

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    Congrats on that fine old amp. Enjoy!
     
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  6. Dana Rudd

    Dana Rudd Tele-Afflicted

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    Got impatient and posted a duplicate.
     
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  7. Telekarster

    Telekarster Friend of Leo's Gold Supporter

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    Nice amp man! Wow.... that thing is in amazing condition for being gig'd with all these years! Being all original, any chance of a death cap situation?
     
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  8. HD28

    HD28 Tele-Meister

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    After a test drive where I plugged in the supplied mis-matched tubes and powered it on hoping the death cap hadn’t failed, it was evident that the rock star seller and the amp tech for the big name rock star who worked on this, may have fibbed.
    The tremolo does not work.
    It has a nice mellow sweet clean and crisp tone through a 1981 Traynor cabinet with 410 eminence squareback speakers. Not obnoxious nor invasive. Just clean and low.
    Now the investigation begins.
    I will post updates and questions as they arise.
     
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  9. Paul G.

    Paul G. Friend of Leo's

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    Replace all the electrolytics. Check the dropping resistors in the doghouse. Check the screen and grid resistors on the output tubes. Replace the bug. Check that the bias voltage is stable and within range.

    Put all the original parts in a box and don't lose them (in case you ever sell the amp to a "collector").

    Then check it out. You'll love it even more.
     
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  10. HD28

    HD28 Tele-Meister

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    I’m on it!
     
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  11. nedorama

    nedorama Tele-Holic

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    Congrats! I had a 65 Bandmaster and loved that amp. I had bought a replacement SurfBug opto unit, but that was 15 years ago...
     
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  12. Greggorios

    Greggorios Friend of Leo's Silver Supporter

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    Cool. Can't wait to hear progress on that beauty.
     
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  13. Engine Swap

    Engine Swap Tele-Afflicted

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    Do you have a foot switch hooked up to the tremolo? Won't work w/o a switch.
     
  14. HD28

    HD28 Tele-Meister

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    Yes, I have a shorting plug.
     
  15. ScottTunes

    ScottTunes TDPRI Member

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    Turned my '64 Bandmaster into a combo (JDNewell cab)... First with 2 vintage Jensen 10s, now a single 12 (still swapping 12s, but like the EVM12L best so far).

    I'm sure you'll enjoy your new vintage Bandmaster!
     
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  16. Timbresmith1

    Timbresmith1 Tele-Afflicted

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    I used to run mine thru 4 of those.

    40 watts can hurt you.
     
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  17. Wally

    Wally Telefied Ad Free Member

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    Nice amp, HD28. Someone took the shell off of that bug, didn’t they? I am not positive that the bulb is original. ???
    If that is a 1965 amp, it was made in the last month. That one filter cap has an EIA code from the 48th week of 1965. Does the tube chart read ‘OL’? There occurred an interesting error in the first month of 1966. Someone forgot to roll the letter for the year for the date stamp forward, and there are tube charts showing that error. There are some with three letters. A corrective ‘P’ is ‘caroted’ in between the erroneous ‘O’ and the month. This error is noted in the ‘Dating Fender Amp’ articles; and there is a January, 1966 Pro Reverb around here with such a correction….O-P-A. It is possible that a January, 1966 amp left the factory without that correction….such an amp would read ‘OA’.
     
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  18. HD28

    HD28 Tele-Meister

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    That’s very interesting Wally, thank you.
    Unfortunately the tube chart is missing.
    Once the parts I’ve ordered come in I no doubt will have further questions regarding the tremolo circuit and will let y’all know.
     
  19. HD28

    HD28 Tele-Meister

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    Baseline readings and observations.
    The tremolo speed pot had a missing or very poor solder joint on lug 3. Very small amount of solder, looks like it was overlooked at Fullerton or a bump may have broken the weak joint…
    I removed the piece of tape covering the tremolo bug/roach and made a bedroll out of some fancy black sealing tape I had. Wrapped the photocell and bulb, open on both ends.
    I used an iPhone tone generator and pushed a signal through the vibrato channel 1. Shorted the tremolo RCA jack and turned it on. The bug flashes and the signal has tremolo. Don’t know why it didn’t work before, perhaps not enough bedroll or tape. But it works now.
    I used a wooden chop stick to connect the lug to the resistor off and on. It made no difference.
    Wall 121.9VAC
    Heater 6.93VAC
    Both red leads from the PT to the diodes 341VAC
    Leaving the bias e-cap -59.6VDC
    V6 P1 -53.1VDC
    V6 P3 463VDC
    V6 plate 458VDC, current 24mA
    V5 P1 -52.7VDC
    V5 P3 463VDC
    V5 plate 458VDC, current 25mA
     

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  20. Wally

    Wally Telefied Ad Free Member

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    HD28, you want to read the bias voltage on pin5 of the power tubes. Pin 1 on a 6V6 and a 6L6 is blank. It is used as a contact point for the control grid stopper resistor. It does not hurt to check the bias supply on pin 1, but pin 5 is the control grid where that bias voltage has to be applied. Example…you could have proper bias voltage on pin 1, but an open resistor would not allow that voltage to reach the control grid P5.
    The same is true for pin 6, which is also a blank pin on the 6V6 and 6L6. Pin 4 is the screen grid to which the voltage needs to be applied. You could have voltage on pin 6 and an open screen grid stopper resistor would prevent voltage from being applied to the screen grid….and the tube would not operate.
     
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