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    Philips 5R4GYS rectifier ok in ST-70 ?

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    deluxmon

    Posts : 17
    Join date : 2013-03-20
    Age : 62
    Location : DENVER

    Philips 5R4GYS rectifier ok in ST-70 ?

    Post by deluxmon on Tue Mar 11, 2014 5:47 pm

    Can I substitute a  Philips 5R4GYS rectifier for a GZ34 in my VTA ST-70?  I read an article by Bob Levi (http://positive-feedback.com/Issue68/5R4GYS.htm) where he says he used one of these Philips 5R4GYS rectifiers in an ST-70 and I quote "The 5R4GYS is totally compatible with the GZ34/5AR4 so no worries..." Has anyone here tried one of these in their VTA ST-70 rig? It is such a great looking tube that I went ahead and ordered one and now I am second guessing myself.....Any thoughts, comments, suggestions or reviews would be most welcome.....


    Last edited by deluxmon on Tue Mar 11, 2014 5:56 pm; edited 1 time in total (Reason for editing : didn't complete my thought.)

    Sal

    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by Sal on Tue Mar 11, 2014 6:05 pm

    You can use the 5R4 with no problems. The B+ will be a little lower but you can just re-bias your tubes. I have a 5R4 installed in my basement ST-70...

    deluxmon

    Posts : 17
    Join date : 2013-03-20
    Age : 62
    Location : DENVER

    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by deluxmon on Tue Mar 11, 2014 6:29 pm

    Thanks Sal.....you've put what's left of my mind at ease ;-)

    sKiZo

    Posts : 1312
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by sKiZo on Tue Mar 11, 2014 9:27 pm

    I liked mine ... till it went south. Quite quickly, matter of fact ...

    http://dynacotubeaudio.forumotion.com/t1649-philips-5r4gys-rectifier?highlight=Philips+5R4GYS

    Luck of the draw maybe. Hope you do better!

    (so much for peace of mind, eh.)  geek

    Finally went with a NOS Mullard GZ37, so it's not all bad.

    PS ... the Phillips did look real nice with the big bottle KT120's ...


    deluxmon

    Posts : 17
    Join date : 2013-03-20
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    Location : DENVER

    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by deluxmon on Wed Mar 12, 2014 1:52 pm

    Skizo is your beautiful rig an ST-70? Wow
    I'll look into finding a GZ37 as a back up should the Philips 5R4GYS fail like yours evidently did.
    I had a friend tell me that using the 5R4GYS in lieu of the GZ34 is like going from a Cadillac to a Kia?
    Thoughts?

    sKiZo

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    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by sKiZo on Wed Mar 12, 2014 6:08 pm

    Mine is an ST120 ... same thing, only different, but it uses the same rectifiers as the ST70.

    I did have a bit of fun with the build ...



    Don't know about the Cadillac vs Kia thing. Both good for what they do. Best I can say is the GZ37 hasn't had any hiccups since putting it in a couple months back, and I work it hard, driving a quad of KT120's at ... significant decibels ...

    If you haven't already done so, do get a copper cap solid state WZ68 as a spare. That's a heavy duty version of the WZ34 that's actually supposed to replace a 5AR4, but it works well, has lots of reserve, and tends to be quite bulletproof in these amps. I've got one, but prefer to use the bottle as my daily driver.

    And luck with the Phillips - as I said, they do get good reviews, but it just didn't work out for me.


    deluxmon

    Posts : 17
    Join date : 2013-03-20
    Age : 62
    Location : DENVER

    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by deluxmon on Wed Mar 12, 2014 6:41 pm

    Thanks for the advice on the WZ68....I'll pick one up. I'm eyeballing a Mullard GZ37 right now and hope to pick one up over the weekend.....Cheers!

    deluxmon

    Posts : 17
    Join date : 2013-03-20
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    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by deluxmon on Thu Mar 13, 2014 6:32 pm

    UPDATE on the Philips 5R4GYS rectifier in a VTA high gain ST-70.....Running KT-77's as power tubes.
    Plugged in the 5R4GYS and though it looks cool as hell, there was (as others warned me of) an obvious loss of power and I could only bias the KT-77's to .370 VDC instead of the .400 I usually run. As for sound - really don't notice too much except for the changes due to loss of power. Next up is a Mullard GZ37......

    sKiZo

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    Re: Philips 5R4GYS rectifier ok in ST-70 ?

    Post by sKiZo on Fri Mar 14, 2014 12:40 am

    If you check the other thread I linked, I believe Bob made some suggestions on a resistor swap that would allow you to bias up properly. Not sure how that would work if you wanted to swap back to a "normal" rectifier for these amps. Most of em bias up towards the top of the pot range anyway, so I don't expect it'd be a problem.

    Once you get it to bias up, that should also take care of your power loss.


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