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Post subject: Pro Jr gets new tubes
Posted: Tue Sep 27, 2011 1:12 pm
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Aspiring Musician
Aspiring Musician
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Joined: Fri Jan 07, 2011 2:51 pm
Posts: 331
Location: Liverpool, England
Hi Guys

I recently bought a 1995 Tweed Pro Jr off ebay.
ImageImage
When I received it I was happy that I had finally got my hands on a tweed made in the USA version, however I was a little unhappy about the amount of hum coming from the amp even before any lead and guitar were plugged in. I did some research on the net and decided that the first course of action was to replace the tubes. From what I have read the tubes insitu were the original ones (pictured below)
Image
2 EL84s, 1 12ax7WB (7025) and 1 12ax7A (7025)

I changed the tubes for the following 2 JJ Tesla EL84s, 1 EH12AU7(gold) and 1 EH5751(gold) (from HotRox UK with a free clip on guitar tuner!!!!) pictured below
Image

and wow what a difference the hum is barley audible, the fan on my brand new pc tower is louder!!!! I am not really after must gain and distortion so the I figured the lower 5751 would give me a cleaner sound and as I don't gig it suits me fine.

The amp has the 10" blue standard emminence speaker so the next mod would be a Celestion G10 Greenback.

I have one question for you though....the 2 JJ EL84s glow quite bright but the other 2 in v2 and v1 especially don't glow very much at all, i have read that this is quite normal these days but if anyone could shed some light (forgive the pun) I would be grateful.

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ukraider
"money cant buy you love but it can buy guitars!!!!!!"


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Post subject: Re: Pro Jr gets new tubes
Posted: Tue Sep 27, 2011 2:00 pm
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Rock Icon
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Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Lower gain preamp tubes (like a 12AU7) don't glow as brightly as the higher gain (like a 12AX7), that is normal. :idea:

Cool amp, looks great! I doubt that the Telefunkens were original though.

BTW, you could try your old tubes one at a time to see if only one of them was causing the noise, the others might be good for spares. Example, put the old tube back in V1, if no noise, tube is good, if noise tube is bad. Then put the new tube back in V1, then try the second old tube in V2, then the same with the output tubes. :idea:

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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