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Line voltage killing tube amps?

 
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WildIowa



Joined: 06 Mar 2004
Posts: 490
Location: Henderson IA

PostPosted: Mon May 25, 2015 6:27 am    Post subject: Line voltage killing tube amps? Reply with quote

GRRRRR! My Citation II power amp took a dump again yesterday. Rebuilt but troublesome, I have had recent issues with blowing fuses and weird stuff. Yesterday literal fireworks and audible bangs. Pulled it apart and one KT88 looks like a bomb went off underneath, took out grid resistors, screen resistors, burnt wiring an inch up the line from each pin...holy crap.

As I have said here before my line voltage is 125 often brushing up against 126 VAC. This old stuff was made for 115-117 VAC and by the time it runs through the trannys etc. you are looking at voltages quite a bit higher than the original design. I rarely power up any other tube stuff here, most of the time gigs in bars etc. and no problems, but the old Silvertone is more forgiving I guess. My power company says 125 is normal and by regs they can go up to 126. Definitely time for a Variac. Is this line voltage now common across the US??
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tangelolemon



Joined: 26 Jan 2009
Posts: 2691
Location: Brooklyn, NY

PostPosted: Mon May 25, 2015 6:48 am    Post subject: Reply with quote

yeah, pretty normal stuff.

Though a good KT88 should be able to take a 5% margin over spec.
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Kregg



Joined: 22 Apr 2008
Posts: 3334
Location: Atlanta

PostPosted: Mon May 25, 2015 7:26 am    Post subject: Reply with quote

I live in an area that seems to eat electronic devices, including my whole house stereo (now obsolete Wink ) and two of my HVAC circuit boards.
I run my good stuff through a Richard Gray's line conditioner, but, there are cheaper ways to go about it.
There are probably ways to regulate voltage at the meter, but, it's probably very expensive and a strong enough power surge can still knock through panels.
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RandyM



Joined: 10 May 2008
Posts: 6716
Location: Austin Texas

PostPosted: Mon Jun 15, 2015 3:13 pm    Post subject: Reply with quote

I run vintage tube stereo gear on a Variac.
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66rdster



Joined: 20 Oct 2013
Posts: 100
Location: Clayton, NC

PostPosted: Tue Jun 16, 2015 5:55 am    Post subject: Reply with quote

I've ran into the problem of high mains voltage at my house too. I found an article at Geofx that addresses the issue. I ended up building the adapter described in the article and it works great. Much cheaper than a Variac or other devises. Here's a link to the article. Maybe its something that would work for you too.
Mike

http://www.geofex.com/article_folders/vintvolt/vintvolt.htm
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tab



Joined: 11 Dec 2008
Posts: 1276
Location: Portland, Or.

PostPosted: Sat Oct 24, 2015 9:14 pm    Post subject: Reply with quote

66rdster wrote:
I've ran into the problem of high mains voltage at my house too. I found an article at Geofx that addresses the issue. I ended up building the adapter described in the article and it works great. Much cheaper than a Variac or other devises. Here's a link to the article. Maybe its something that would work for you too.
Mike

http://www.geofex.com/article_folders/vintvolt/vintvolt.htm


No vintage amps here but I have friends that have a few and like the simple fix. Thanks for the link.
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