Author Topic: Sentura I tube question....  (Read 1118 times)

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Offline wilddeath

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Sentura I tube question....
« on: February 16, 2010, 04:23:08 pm »
Just picked up a Sentura I! I'm happy to be back with a Sunn amp again, this one came with no tubes.  After seeing what I had around i stocked it with everything but the 7199.  I'm gonna see if any of the locals carry one worse case i'll  rewire the socket to take a 6u8. Anyway... history tells me that the Sentura I was 40 watts courtesy of a pair of EL34's. Sentura II is rated at 60 watts with a pair of 6550's.  Is it as simple as swapping the tubes and doing a bias with these amps? Or does it run deeper... did the Sentura II come equipped with more powerful iron to accompany the extra wattage?


Offline loudthud

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Re: Sentura I tube question....
« Reply #1 on: February 16, 2010, 04:35:41 pm »
Yep, iron is different. In a recent thread I measured the height of the transformers for those cases where there are 40 and 60 watt versions of amps that had the same name.

Offline wilddeath

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Re: Sentura I tube question....
« Reply #2 on: February 17, 2010, 06:01:56 pm »
OK i'm gonna keep it as is. 

I found a 7199 today and popped it in.  It powered on, nothing blew up.  I have almost NO volume.  With it on 10 i can hear a faint overly distorted signal coming through the speaker.  I'm gonna go out on a limb and say its the caps.  I checked all the tubes with spares, they work. The only one I cant check is the 7199, which oddly enough was cold when i pulled it. Any time i've had a bad phase inverter i've seen the tubes flash....  So this leads me to the obvious,  Caps.  Really low distorted volume is the Filter caps if I remember correctly?? Do they make replacement cans, also are there any other caps I should consider changing.   My budget as of lately prohibits I bring it to the service center. 

Offline wilddeath

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Re: Sentura I tube question....
« Reply #3 on: February 17, 2010, 06:22:57 pm »
Scratch that,  just remembered I didn't check the Rectifier.  Went down stairs pulled one off the shelf, popped it in and fired her up!  WOW!  My nuts are tingling! 

But i'm not ruling out the phase inverter being on the fritz;  Tubes are running very hott, i can smell the heat. Also theres lots of buzzes and pops, very loud at times.  But the tone is spot on, crystal clear, no oddball harmonics.  Phase inverter, i'm on to you. 

Offline Soundmasterg

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Re: Sentura I tube question....
« Reply #4 on: February 19, 2010, 04:27:30 am »
From your description of the amp it sounds like the electrolytic caps in the amp, and possible some plate load resistors in the preamp need to be replaced. If the elytic caps are bad enough, they could fail, causing the power transformer to fail when they go. If the caps are original, then they should be replaced before you play the amp.

Greg