Repair Question - 1967 yba-1 | The Canadian Guitar Forum

Repair Question 1967 yba-1

Discussion in 'Amp Building/Technical/Repair' started by Moosehead, Dec 11, 2019.

  1. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    Just picked up what looks to be all original yba-1. I've never messed around with amps much but i do have some electronics experience and work around electricity all the time (i know how to discharge a cap). This thing hasn't been fired up in years.

    From first glance:

    No rectifier tube - kind of a bummer but its one less tube to buy
    Original tubes - 3x rogers 12ax7 and 1x rca el34
    One tube looks like it went spectacularly ( halo of brown around tube socket)
    Fuse is good
    2 prong plug needs to go
    Almost all solder connections have the nail polish on the connections

    Question 1: If I was a tech what would I check before firing it up?

    Question 2: Whats the danger (to the amp) of putting new power tubes in and firing it up?
     
  2. sambonee

    sambonee Gold Member

    Joined:
    Dec 20, 2007
    Location:
    Milton, on
    good find. hope you're well. chat soon,

    Sean
     
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  3. jb welder

    jb welder

    Joined:
    Sep 13, 2010
    Location:
    Melonville, Canada
    Any bulging or venting on the larger caps? Does it have the brown rectangular box like parts at the power tube end of the board? (darker brown) Post some gut shots if you can.
    Was it in use, or sat for a long time? If it was in use, I'd not worry so much about firing it up.
    Otherwise, in extreme cases damage can be done before the fuse has time to blow. A lightbulb/lamp limiter is easy to build and will protect the amp when powering up if anything is faulty (if you use something like a 100W bulb).
    Like this picture. Switch is not necessary and of course you plug in an amp rather than a radio. :)

    [​IMG]

    Powering Your Radio Safely with a Dim-bulb Tester
     
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  4. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    Yba1 - Google Drive

    Nothing appears to be bulging. I don't think its been fired up in a long time.
     
  5. Lincoln

    Lincoln Gold Member

    Joined:
    Jun 2, 2008
    Location:
    Fort Saskatchewan, Alberta
    that's some big iron you've got there. Very nice old amp
     
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  6. Frenchy99

    Frenchy99

    Joined:
    Oct 15, 2016
    Location:
    North Pole
    Congrats on your purchase!

    Would verify if nothing brunt inside, see if any resistors would need replacing. Then would put on a variac ( speaker load needs to be on amp ) without any power tubes in and would gently increase power levels not to shock the dried out Caps. if everything lights ups correctly, start over with power tubes in.

    Good luck !
     
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  7. jb welder

    jb welder

    Joined:
    Sep 13, 2010
    Location:
    Melonville, Canada
    Agree with Frenchy above, but if you don't have a variac, the bulb limiter can be used instead for 'soft' power up (when used with appropriate wattage bulb).
     
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  8. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    So when the amp is not turned on (no pwr tubes in) the 100w bulb is lit dimly on the tester and the red jewel light on the amp lights up

    Turning the amp on the bulb lights up more brightly but not full brightness. shut it off quickly

    Why would the jewel light up when the amp is off?
     
    Last edited: Dec 14, 2019
  9. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    nevermind, there is an a/c switch on the back of the amp. switch on the front is just a standby
     
  10. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    It's alive. Noisey but it works. jumpered the inputs but it sounded like garbage. It will need a trip to the tech but I'm happy to know its in working condition.

    Today im going to replace the power cord with a 3 prong. I was more than a little nervous plugging in the guitar with the 2 prong cord. non contact voltage tester was going crazy, even on hte patch cord to the guitar.
     
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  11. Frenchy99

    Frenchy99

    Joined:
    Oct 15, 2016
    Location:
    North Pole
    Congrats !!!

    Sounds like you just need a cap job. Normal given its age...

    You'll be jamming in no time! ;)
     
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  12. dtsaudio

    dtsaudio

    Joined:
    Apr 15, 2009
    Location:
    Hamilton, ON
    Have you dated it, to see if it is a 67. There's about 5 different versions of this amp. All are good, mostly changes due to parts availability. I see yours has the filter choke which makes it a pretty early version.
     
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  13. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    So I've replaced the 2 prong with a grounded cord and removed the "death cap". Cleaned pots too.

    Popped in some new JJ's (el34) and she sounds great on vol 1.

    Vol 2 is giving me some horrible screeching. Unusable atm.

    What is the proper way to ground the power cord?
    Read on tgp that it should be bonded. I just soldered it to the closest solder blob on the chassis. I suppose i could drill a hole and fasten it with a bolt and lock nut. Seemed like too much work at the time.
     
  14. dtsaudio

    dtsaudio

    Joined:
    Apr 15, 2009
    Location:
    Hamilton, ON
    What you did is okay, in that it will work and provide some grounding. However, the correct way is to use a ring terminal, crimped and soldered to the wire, and bolted to the chassis using a new screw, with a lock nut.
    So drill that hole.

    Your screeching on volume 2 may be the volume control itself or could be a bad jack.
     
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  15. Moosehead

    Moosehead

    Joined:
    Jan 6, 2011
    Location:
    Niagara
    I DO NOT LIKE FRIED RESISTORS AND HAM!
    I DO NOT LIKE THEM SAID SAM I AM

    I DO NOT LIKE THEM IN MY AMP
    I DO NOT LIKE THEM WHEN I CAMP
    NOR DO I LIKE THEM WHEN I RARELY GET THE CHANCE TO JAM

    I DO NOT LIKE FRIED RESISTORS AND HAM!




    PEAMEAL ALL THE WAY!
     
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