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    Soft start rectifier for ST70

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    poconoman

    Posts : 106
    Join date : 2013-01-17

    Soft start rectifier for ST70

    Post by poconoman on Sat Jan 26, 2013 2:58 pm

    Has anyone tried these? They say it give 30 seconds to warm everything up. Ebay Item number:190630611170 and this one, 15 seconds. Item number:190659782385

    Any thoughts?

    peterh

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    Location : gothenburg, sweden

    Re: Soft start rectifier for ST70

    Post by peterh on Sat Jan 26, 2013 3:30 pm

    poconoman wrote:Has anyone tried these? They say it give 30 seconds to warm everything up. Ebay Item number:190630611170 and this one, 15 seconds. Item number:190659782385

    Any thoughts?
    Sounds awfully simular to gz34 ( 5au4 )

    poconoman

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    Re: Soft start rectifier for ST70

    Post by poconoman on Tue Jan 29, 2013 11:15 am

    If I get the SS soft rectifier, does it eliminate the recommendation of the yellow sheet mod?

    peterh

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    Re: Soft start rectifier for ST70

    Post by peterh on Tue Jan 29, 2013 5:02 pm

    poconoman wrote:If I get the SS soft rectifier, does it eliminate the recommendation of the yellow sheet mod?
    What is "the yellow sheet mod " ?
    And why even bother replacing the tube rectifier ? It does all softstart you ever need for you.
    The only reason would be to save money, but do we use tube amps to save money in the first place ?

    Bob Latino
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    Re: Soft start rectifier for ST70

    Post by Bob Latino on Tue Jan 29, 2013 10:30 pm

    The yellow sheet mod is really only for a tube rectifier. I don't feel you would need the mod if you used a solid state rectifier. The "yellow sheet mod", by the way, is here > Yellow sheet mod

    Bob

    poconoman

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    Re: Soft start rectifier for ST70

    Post by poconoman on Wed Jan 30, 2013 10:23 am

    Bob Latino wrote:The yellow sheet mod is really only for a tube rectifier. I don't feel you would need the mod if you used a solid state rectifier. The "yellow sheet mod", by the way, is here > Yellow sheet mod

    Bob

    Thanks Bob, I kinda figured that. Can you check the ebay SS rec and give your opinion? Over priced, scam?

    Thank you

    Bob Latino
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    Re: Soft start rectifier for ST70

    Post by Bob Latino on Wed Jan 30, 2013 10:39 am

    A 5U4 does warm up quicker than a 5AR4 but IMHO any TUBE rectifier does NOT need any type of soft start assistance. That is my opinion but others may have a differing opinion.

    Bob


    Last edited by Bob Latino on Wed Jan 30, 2013 4:28 pm; edited 2 times in total

    tubes4hifi
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    Re: Soft start rectifier for ST70

    Post by tubes4hifi on Wed Jan 30, 2013 3:42 pm

    Bob skipped a word there NOT - if you have a tube rectifier, you have soft start.
    If you have a SS rectifier, then you NEED a soft start or a delay circuit like our TDR.

    Bob Latino
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    Re: Soft start rectifier for ST70

    Post by Bob Latino on Wed Jan 30, 2013 4:31 pm

    Hi Roy,

    Thanks for finding that typo .... I did forget the word "NOT". I corrected that typo above and put the word "NOT" in red ..

    Bob

    poconoman

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    Re: Soft start rectifier for ST70

    Post by poconoman on Wed Jan 30, 2013 5:42 pm

    tubes4hifi wrote:Bob skipped a word there NOT - if you have a tube rectifier, you have soft start.
    If you have a SS rectifier, then you NEED a soft start or a delay circuit like our TDR.

    According to this Ebay Item number:190630611170, it gives 30 seconds of warm up. Do you know someone that has this or something similar and it does indeed work?

    peterh

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    Re: Soft start rectifier for ST70

    Post by peterh on Thu Jan 31, 2013 3:25 am

    poconoman wrote:
    tubes4hifi wrote:Bob skipped a word there NOT - if you have a tube rectifier, you have soft start.
    If you have a SS rectifier, then you NEED a soft start or a delay circuit like our TDR.

    According to this Ebay Item number:190630611170, it gives 30 seconds of warm up. Do you know someone that has this or something similar and it does indeed work?
    A stock st-70 with a gz34 has that delay. What are you trying to
    do that a gz34 cannot ?

    If the goal is to replace a tube rectifier then 2 1n4007 soldered
    in the gz34 socket is all you need ( there is no need for a delayed
    + as long as the caps will stand the voltage until the tubes start to draw current. And the st70 does not reach that limit ( until i stand
    corrected).
    My advice is to put your money elsewhere.

    poconoman

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    Re: Soft start rectifier for ST70

    Post by poconoman on Thu Jan 31, 2013 10:18 am

    I'm going to try this again.

    The ebay SS rec claims that it allows 30 seconds of warm up. Just as a 5ar4. My idea is if this SS does give 30 seconds, then there's no need to soder the diodes. Do you understand now?

    peterh

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    Re: Soft start rectifier for ST70

    Post by peterh on Thu Jan 31, 2013 2:30 pm

    poconoman wrote:I'm going to try this again.

    The ebay SS rec claims that it allows 30 seconds of warm up. Just as a 5ar4. My idea is if this SS does give 30 seconds, then there's no need to soder the diodes. Do you understand now?
    Yes, if you install a gz34-emulator i assume it can stand the voltage.

    The reason for the diodes in combination with gz34 was protect some units that flashed under some conditions.

    tubes4hifi
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    Re: Soft start rectifier for ST70

    Post by tubes4hifi on Fri Feb 01, 2013 2:22 pm

    used to list for $28, now lists for $98 . . . interesting ?? I could buy alot of 5AR4 tubes for $98 !!

    peterh

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    Re: Soft start rectifier for ST70

    Post by peterh on Fri Feb 01, 2013 3:29 pm

    tubes4hifi wrote:used to list for $28, now lists for $98 . . . interesting ?? I could buy alot of 5AR4 tubes for $98 !!
    yes, even more 1n4007 if you want SI-rectifiers.

    poconoman

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    Re: Soft start rectifier for ST70

    Post by poconoman on Fri Feb 01, 2013 3:42 pm

    tubes4hifi wrote:used to list for $28, now lists for $98 . . . interesting ?? I could buy alot of 5AR4 tubes for $98 !!

    Which brand do you usually get?

    poconoman

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    Re: Soft start rectifier for ST70

    Post by poconoman on Fri Feb 01, 2013 3:45 pm

    peterh wrote:
    tubes4hifi wrote:used to list for $28, now lists for $98 . . . interesting ?? I could buy alot of 5AR4 tubes for $98 !!
    yes, even more 1n4007 if you want SI-rectifiers.

    Dicided to get some diodes and do the simple mod. Maybe the Ruby rec will last longer.

    Pillo69

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    Re: Soft start rectifier for ST70

    Post by Pillo69 on Fri Feb 01, 2013 3:54 pm

    Change rectifier tube brand.
    The first in my ST70 RUBI went in a week (pin 4 valve). I put the diodes as advised RUBI Bob and other new and went in a month (pin 6 of the valve).
    Then use a SOVTEK takes six months and in perfect condition, including the 1N4007 diodes.
    It would be advisable to seek a tube rectifier old, are better than today.

    Jim McShane

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    Location : South Suburban Chicago

    Re: Soft start rectifier for ST70

    Post by Jim McShane on Fri Feb 01, 2013 11:20 pm

    Pillo69 wrote:Change rectifier tube brand.
    The first in my ST70 RUBI went in a week (pin 4 valve). I put the diodes as advised RUBI Bob and other new and went in a month (pin 6 of the valve).
    Then use a SOVTEK takes six months and in perfect condition, including the 1N4007 diodes.
    It would be advisable to seek a tube rectifier old, are better than today.

    I am surprised to hear the continuing problems after adding the diodes as Bob L. suggests. Before I forget though, don't use 1N4007s, use the quieter and faster UF4007. They are far superior and only a few cents more expensive.

    Also, "Ruby" is a rebrander, they do not make tubes. The chances are the Ruby 5AR4 you had was Chinese made.

    If you continue to have rectifier problems I'd suspect you have a problem with the first filter cap. How old is your ST-70? And does it still have the original filter cap? With the diode mod in place and a healthy 1st filter cap you should be fine. But if the old cap is worn out then you'll have trouble.

    Pillo69

    Posts : 105
    Join date : 2012-04-11
    Location : Granada (España)

    Re: Soft start rectifier for ST70

    Post by Pillo69 on Sat Feb 02, 2013 9:06 am

    My ST70 possessed a new filter capacitor with the original values ​​of Dynaco, I changed it for AuthentiCap (German) of 80-40-30-20 and 550v.

    The power transformer (PA-060) sent him to rewind to the current tension in my area (240v.), they placed an electrostatic shield between primary and secondary to prevent noise from the network, the amperage for filaments (6.3 v .) rose to 5.5 Amp. and amperage for a 4 Amp rectifier tube., the top cover of the transformer underwent a change at the back to prevent condensation inside.

    The capacitors of the printed circuit board is replaced by a Sprague Orange Drop and resistors all new larger watts and 1% metal film.

    The 7 output terminal of the two resistors placed Bob recommended for adjusting Bias and the two diodes in the rectifier tube socket (look for the UF4007). The problem is not think the diodes but by the quality of the rectifier valve.

    Power tubes are Electro Harmonix 6CA7 four new, very good acting.

    But with the tube rectifier RUBI've had many problems and I will not be using.



    Jim McShane

    Posts : 154
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    Location : South Suburban Chicago

    Re: Soft start rectifier for ST70

    Post by Jim McShane on Sat Feb 02, 2013 5:07 pm

    Just be sure that the 80 uf section is not the section installed right after the rectifier tube. That is too high for 5AR4, the limit is 60 uf. While 20 uf isn't much over it does stress the tube more than using the 40 uf section for instance.

    Pillo69

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    Re: Soft start rectifier for ST70

    Post by Pillo69 on Sat Feb 02, 2013 7:34 pm

    I placed as recommended by Bob, I think it was 80 uF back toward PA-060 transformer, but I speak from memory, but I followed the instructions of Bob.

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