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 Post subject: Rectifier tube advice
PostPosted: Fri Sep 16, 2016 10:53 am 
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Bottle Rocket

Joined: Wed Sep 14, 2016 2:59 pm
Posts: 5
Hi everyone,

I just checked and the rectifier tube that went installed in my second hand LSS is a 5U4GBEH Electro Harmonix Made in Russia 02 06. That's all I see printed on that one. I know the amp was build to use a Philips JAN 5Y3. I know too from MB that my amp is above the first series that had a higher rate of failure due to lower specs modern tube, that the current JJ are way better than the russian that were used a few years ago and failed often.

So, the "Made in Russia" on my EH makes me suspicious, and also 5U4G is this the same as the 5Y3 in spec? Does it have an impact on the tone of the amp (different 'sag'? don't know neither what it means nor the effect it could have)?

Should I search for a NOS Philips JAN 5Y3? Or maybe you can point me good and not too expensive alternatives?

Many thanks already, this forum is so rich in advices, hindsights, amp settings and much more that I can not stop reading it at the mo :-).

Thanks already for you help and advices.

Greg


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PostPosted: Fri Sep 16, 2016 12:23 pm 
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Bottle Rocket

Joined: Wed Sep 14, 2016 2:59 pm
Posts: 5
Just a precision:

in the amp, I still have the two 470Ohms 10% 1W and the two 100Ohms 10% 1W resistors in place on the sides of the ribbon connector. So it seems truely nothing was modded.

And I checked too , the reverb jack is a TS only, so it will have to be replace to have the Drive switch mod on this jack (TRS, like the current channel/solo footswitch)

Again, thanks for you help and advice on this tube matter :-)

Greg


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PostPosted: Fri Sep 16, 2016 6:44 pm 
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Mark IV
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Joined: Sun Feb 17, 2008 4:02 pm
Posts: 522
http://tctubes.com/GE-5Y3GT-ribbed-gray-plates.aspx

_________________
When Gibsons are outlawed, only outlaws will have Gibsons


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PostPosted: Mon Sep 19, 2016 8:31 am 
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Bottle Rocket

Joined: Wed Sep 14, 2016 2:59 pm
Posts: 5
Ok, thanks for the link.

From what I read also, the 5U4GBEH Electro Harmonix in my amp is maybe a safe bet, driving the power tubes a bit less hard. True or not?

I found also this searching on the forum:

viewtopic.php?f=31&t=57779

Did someone did that mod on the capacitors?

What is the effect of removing the two 470 ohms resistors (appart from modifying the parallel resistors global value to the left alone one)? What is this resistor doing in the circuit? And the capacitors?

And also, did someone followed the recommendation to replace the carbon resistors by metal ones?

Again, I know this is old stuff for a lot of people here, but as I just bought this one, I'd like to understand the best I can the things related to this amp.

Thanks for any advices and answers on this matter,

Greg


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PostPosted: Mon Sep 19, 2016 4:56 pm 
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Bottle Rocket

Joined: Wed Sep 14, 2016 2:59 pm
Posts: 5
The mod consisting or removing the two 470 Ohms resistors seems also a rather adventurous one; yes, it will result in a resistor of 100 Ohms instead of 82,45 Ohms, limiting so the current going to the rectifier tube, but two parallel resistors somehow cumulate (not perfectly) their power handlings. Removing one of the two halves so the power rating of this part of the circuit.

Wouldn't it be better to replace the 470 Ohms and 100 Ohms by two 200 Ohms, achieving so also 100 Ohms, but still with their power handlings cumulated (here completely, the two resistors being identical in theory)?

I think this would avoid what can be seen here:

http://www.seymourduncan.com/forum/show ... e-Glassman

It seems the only left resistor was baked by the passing current.

What do you think?

Greg


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