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Post subject: Re: plate voltage
Posted: Fri Mar 08, 2019 3:07 am
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I'd like to thank everyone! I think I have to do a "hard servicing" to my amp. After 53 years it deserves it!


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Post subject: Re: plate voltage
Posted: Fri Mar 08, 2019 10:21 am
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stratele52 wrote:
vinyl wrote:
vinyl wrote:

Perché quello che hai postato, credo che tu abbia bisogno di nuovi tappi elettrolitici. Non parlo italiano, ma credo anche che l'italiano sia la tua prima lingua. ...Anno 1966 )


Translation ;

Because what you posted, I think you need new electrolytic filter caps. I do not speak Italian, but I also believe that Italian is your first language....( Anno 1966)


Stratele52,

Thanks for posting the translation, I should have included that in my post. I was trying to encourage Francesco to provide more information to allow the many experts here like you to provide some help.

More to the point, PICTURES!

If the capacitors have never been replaced, then they are probably due. But there are other reasons that the plate voltage could be low. That's why I asked if the amp was a domestic or export.

I read somewhere else you are traveling to London soon.
Bon Voyage, Mon Ami


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Post subject: Re: plate voltage
Posted: Fri Mar 08, 2019 7:31 pm
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Rock Star
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stratele52 wrote:
Nothing wrong , plate voltage varies with tubes bias and with you house wall outlet voltage;

Colder bias = higher plate voltage
Hot bias = lower plate voltage

That is why we must alway read plate voltage when doing amp bias


Sorry, for my late entry. Simple question. Does the amp have a GZ34/5AR4 rectifier or a 5U4GB? The 5U4GB often has a 10-20VDC drop in B+ voltage, versus the GZ34. Both tubes, in same state of health.

Thanks! :)


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Post subject: Re: plate voltage
Posted: Fri Mar 08, 2019 9:20 pm
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From page one of this thread......

Francesco48 wrote:
Rectifier tube is GZ 34 and it's brand new, 6L6s too are brand new.
Caps are some year old but they look good.
Rectifier, when stand by switch is off, gives 500 DC volts.
But when I switch it on voltage goes down to about 435 instead of 465.
another curios thing is that when i switch stand by off voltage goes to 0 immediately!
I mean caps discarge in a few seconds.
Thanks for helping me.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: plate voltage
Posted: Sun Mar 10, 2019 5:19 pm
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Well then... I guess it's tired main PSU caps or OP bought a weak, new rectifier (it happens). Do you have another one to try in the amp?


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Post subject: Re: plate voltage
Posted: Mon Mar 11, 2019 10:33 am
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Grazie, Vinyl. Tappi elettrolitici mi fa sorridere :) You're right, I'm Italian but "ANNO" first of all is latin and then ... italian :D


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