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    Electric Zap sound and shut off on my VTA ST-70

    James_Weir
    James_Weir

    Posts : 10
    Join date : 2016-07-01
    Age : 46
    Location : Los Angeles

    Electric Zap sound and shut off on my VTA ST-70 Empty Electric Zap sound and shut off on my VTA ST-70

    Post by James_Weir on Sat May 02, 2020 6:32 pm

    I built the VTA ST-70 a couple of years ago and 4 or 5 months ago started hearing a loud zapping sound similar to the sound a taser makes, but only on rare occasions. A few days ago I came in from another room to flip the record and realized none of the tubes were glowing. I shut the unit off, waited 10 minutes, and turned it back on with no problems. Just now had the same issue which seemed to coincide with the zap sound. Any suggestions about the cause and possible solutions would be super helpful.
    Bob Latino
    Bob Latino
    Admin

    Posts : 2904
    Join date : 2008-11-26
    Location : Massachusetts

    Electric Zap sound and shut off on my VTA ST-70 Empty Re: Electric Zap sound and shut off on my VTA ST-70

    Post by Bob Latino on Sat May 02, 2020 7:40 pm

    James_Weir wrote:I built the VTA ST-70 a couple of years ago and 4 or 5 months ago started hearing a loud zapping sound similar to the sound a taser makes, but only on rare occasions. A few days ago I came in from another room to flip the record and realized none of the tubes were glowing. I shut the unit off, waited 10 minutes, and turned it back on with no problems. Just now had the same issue which seemed to coincide with the zap sound. Any suggestions about the cause and possible solutions would be super helpful.

    Hi James,

    1. Try a new rectifier in your amp .. Don't use a JJ or a Sovtek 5AR4 .. The Tung-Sol 5AR4 is very good and is what I ship will all the VTA ST-70 amp kits. I don't guarantee that this is the problem but it could be.

    2.  It could also be a bad solder connection now showing up after 2 years of heating up and cooling down (expansion and then contraction). The connection goes "partial" and does not make full contact.

    3.  It could also be an output tube starting to go bad ? Try a new set of output tubes

    4. It could be a contact issue. Dust between socket pins and tube pins prevents full contact between the socket and the tube.

    Bob
    James_Weir
    James_Weir

    Posts : 10
    Join date : 2016-07-01
    Age : 46
    Location : Los Angeles

    Electric Zap sound and shut off on my VTA ST-70 Empty Re: Electric Zap sound and shut off on my VTA ST-70

    Post by James_Weir on Sat May 02, 2020 9:17 pm

    Thanks! Ordered the new Tung-Sol. It's running on what must have been the GE 188-5 that came with it before I did the VTA conversion. If that doesn't solve it I'll be back to ask about identifying a bad solder connection.

    And thanks for being such a great resource when I was doing the original upgrade as well as this issue. Go Pats.

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    Electric Zap sound and shut off on my VTA ST-70 Empty Re: Electric Zap sound and shut off on my VTA ST-70

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