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    gz34 vs 5y3 vs 5u4

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    rfbro

    Posts : 26
    Join date : 2014-12-28
    Age : 61
    Location : Vancouver WA

    gz34 vs 5y3 vs 5u4

    Post by rfbro on Sat May 21, 2016 10:09 pm

    Wondering if it is ok to use a 5y3 or 5u4 in place of a 5ar4 in my ST 120

    Tubes4ever

    Posts : 61
    Join date : 2015-07-14
    Location : Star, Idaho

    Re: gz34 vs 5y3 vs 5u4

    Post by Tubes4ever on Sun May 22, 2016 1:15 am

    rfbro wrote:Wondering if it is ok to use a 5y3 or 5u4 in place of a 5ar4 in my ST 120

    You can't use a 5y3 since it is rated at 125mA max. You can use a 5u4GB as it is rated at 275mA. The recommended bias setting for the ST120 tubes is 50 mA each for a total of 200mA plus about 25mA for the VTA board. The 5U4 will work just fine.

    Bob Latino
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    Join date : 2008-11-26
    Location : Massachusetts

    Re: gz34 vs 5y3 vs 5u4

    Post by Bob Latino on Sun May 22, 2016 7:55 am


    This chart has been posted before .. You can probably use any of the rectifiers that are 250 milliamp (or higher) rated (MaxPma). All the VTA amps have 4 amp rated 5 volt rectifier filament lines (Famp) so any rectifier rated below 4 amps current draw will work as long as the MaxPma is 250 milliamps or higher.

    Bob


    Last edited by Bob Latino on Sun May 22, 2016 11:09 am; edited 2 times in total

    Tubes4ever

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    Join date : 2015-07-14
    Location : Star, Idaho

    Re: gz34 vs 5y3 vs 5u4

    Post by Tubes4ever on Sun May 22, 2016 11:00 am

    Bob,

    This should be a sticky. Except change "5 volts bias lines" to 5 volt heater windings.

    Tim

    Bob Latino
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    Re: gz34 vs 5y3 vs 5u4

    Post by Bob Latino on Sun May 22, 2016 11:14 am

    Tubes4ever wrote:Bob,

    This should be a sticky.  Except change "5 volts bias lines" to 5 volt heater windings.

    Tim

    Hi Tim,

    Thanks for pointing out ... I made an appropriate change in the text of that post .. Don't know why I said "bias" line. The bias line is 55 VAC .. That would sure make that rectifier light up pretty bright but > for a very short time - lol ..

    Bob

    tubes4hifi
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    Re: gz34 vs 5y3 vs 5u4

    Post by tubes4hifi on Sun May 22, 2016 12:17 pm

    Bob & all,
    here's an edited version of the list, only tubes with 250ma or better, and only 8 pin tubes . . .

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