1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

One Owner 1969 Super Reverb AB568 Restoration

Discussion in 'Amp Central Station' started by HD28, Apr 4, 2021.

How should this amp be restored and or modified?

  1. Restore the amp cosmetically leaving electronics as-built.

    0 vote(s)
    0.0%
  2. Restore the amp cosmetically, only replacing the filter caps, failed caps and resistors as required

    19 vote(s)
    79.2%
  3. Restore the amp cosmetically and full on blackface the circuit.

    5 vote(s)
    20.8%
  1. BobbyZ

    BobbyZ Doctor of Teleocity

    Posts:
    13,589
    Joined:
    Jan 12, 2011
    Location:
    Snellman MN
    I wouldn't use ArmorAll on my ex-wive's cars.
    And I hate my ex-wives!
     
  2. Wally

    Wally Telefied Ad Free Member

    Posts:
    38,843
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    I particularly do not like the look of any glossy looking treatment on a vintage amp. Ommv.
     
    Willie Johnson and HD28 like this.
  3. Dan German

    Dan German Doctor of Teleocity

    Posts:
    11,261
    Joined:
    Feb 21, 2008
    Location:
    Left of the Left Coast
    I see what you did there...
     
    Wally and HD28 like this.
  4. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    Reapplied the circuit label.
     

    Attached Files:

  5. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    What is the sulfur looking corrosion or stuff? It doesn’t come off easy at all. I’m not too worried about it or the heat discolouration from the power tubes, just wondering.
    Gonna start de-scratching the pots now.
     

    Attached Files:

  6. Ed Storer

    Ed Storer Tele-Afflicted Silver Supporter

    Posts:
    1,140
    Joined:
    May 27, 2010
    Location:
    Seattle WA
    The cosmetics on the amp were pristine when I bought it. I would wipe it down with a damp sponge on occasion, but never a detergent or a silicone like Armorall.

    As far as the bias goes, I prefer adjusting without removing the chassis. I use bias probes. I once bought a 1986 Concert (Rivera era) 2 x 10. The power tubes were a Sovtek 5881 and Electro-Harmonix 6L6GT. The tech must have gone through a lot of trouble getting a pair that would deliver the right bias current. I rewired the bias pot to voltage adjust and put in a matched pair of TAD 6L6WGC-STR tubes, biased to 35 ma per tube and the amp sounded perfect. I gave the mismatched tubes to a friend that dabbled in amp maintenance.

    If you're one that will pull the chassis and probe 400+ Volts with your multimeter, then simply adding a bias trim pot to the existing circuit is great. If you choose to avoid poking your probes into a hot circuit, then I recommend eliminating the bias balance in favor of bias voltage/current and a set of probes so you don't have to take the chassis out of the cab every time you replace power tubes.
     
    HD28 likes this.
  7. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    My question about armorall was pointed at the grill cloth only. The plastic fibers will photo-degrade and off gas and will become brittle, so that when they get touched they will break and, well, that's not a good thing. I gave this one a vacuuming with a firm brush attachment to get rid of the dust. It’s still dirty but the dirt doesn’t bother me, I want to “preserve” the plastic cloth. If I can that is. I don’t know if armorall is only a marketing make things “shiny” product or if it really does make plastics and vinyls last longer...
     
  8. Willie Johnson

    Willie Johnson Tele-Holic

    Age:
    101
    Posts:
    807
    Joined:
    May 24, 2016
    Location:
    Chicagoland
    I thought about cleaning up my SF Princeton since it looked so grubby compared to my PRRI, but thought better of it. Black tolex is a little unglued by the top front corners too, but it's an old amp--let it be old.
     
    HD28 likes this.
  9. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    “Don’t be ashamed of your age” smiley face.
     
  10. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    Please be patient with my noobism.
    I wish to replace the filter caps under the doghouse. Which is what I think the 5 caps in the picture and the schematic snippet.
    Please confirm if I think I know what I think I’m talking about...

    Any advise on what and where to order new electronic components?

    I like Uncle Dougs take on disguising the new caps in the old wrappers. Any thoughts are appreciated.
     

    Attached Files:

  11. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    The 2 resistors between b-c-d read 4.53k ohms and 0.992 k ohms.
     
  12. hepular

    hepular Tele-Holic

    Posts:
    893
    Joined:
    Feb 17, 2019
    Location:
    abilene, tx
    it's a lotta work for an amp that will never be a 55 tweed. ESPECIALLY if you're just gonna be starting with that sorta maintenance. You really really wouldn't want to get one of those installed backwards in its sleeve & not notice. tube amp depot, amplified parts, antique electronics are all pretty similar price-wise for f&t caps.
     
    Paul G., Wally and gridlock like this.
  13. gridlock

    gridlock Poster Extraordinaire

    Posts:
    5,346
    Joined:
    Oct 1, 2011
    Location:
    Tampa, Fl
    Wow, like new.
     
    HD28 likes this.
  14. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    Thank you.
     
    Wally likes this.
  15. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    Death cap underneath 3-way ground switch. There is no continuity through death cap to chassis. Recall that the AB568 circuit does not show a 3-way switch, but this amp has one and was destined for export to Canada.
     

    Attached Files:

  16. VWAmTele

    VWAmTele Friend of Leo's

    Posts:
    3,946
    Joined:
    Feb 24, 2005
    Location:
    FL
    My dream amp - congrats!
     
    HD28 likes this.
  17. Wally

    Wally Telefied Ad Free Member

    Posts:
    38,843
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    imho, tolex should be reglued to prevent further degradation.
     
    HD28 likes this.
  18. Wally

    Wally Telefied Ad Free Member

    Posts:
    38,843
    Joined:
    Mar 17, 2003
    Location:
    Lubbock, TX
    methinks spell checker did that for our amusement! Lol...
     
    Dan German and HD28 like this.
  19. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    While shopping for cap kits I came across this.
    The AB568 shows a 25 uF cap on leg 8 of V5.
    The AA1069 shows a 5uF cap on leg 8 of V5.
    This amp has a 5uF cap.
    Unless there were any interim circuit designs between ab568 and aa1069, this amp is aa1069.
     

    Attached Files:

  20. HD28

    HD28 TDPRI Member

    Posts:
    80
    Joined:
    May 26, 2016
    Location:
    Winnipeg MB
    Can you suggest a source for the hardware and instructions for a bias voltage/current system?
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.