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Old 21st Jan 2020, 1:00 pm   #1215
GrimJosef
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Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: The Audiophoolery Thread.

Quote:
Originally Posted by Radio Wrangler View Post
... I'm not sure about those Hunts little brown capacitors, though. They used to crack up in fairly short order and must have fed and clothed many a repairman's family. They were known about back in the day. They were failing in older sets while they were still being used in new sets ...
Fortunately there's only one of them in the Quad II and it isn't working very hard. It runs between the screen grids of the EF86s. This is quite a neat approach since, as Phil Moss points out, it means that differential mode signals (i.e. the music) are decoupled at the screens by the capacitor but common mode signals (which are typically noise) are not, and the resulting local NFB therefore suppresses them. It also means there's little DC across the capacitor. So if the shell does split and the cap goes a bit leaky the consequences aren't dreadful. I can't ever recall seeing one, split though some are, cause a serious problem.

They were widely used though. Here's a black one in a Beam Echo DL7-35 https://farm2.static.***********/1402...8c29d6e4_o.jpg. Here are some in a Leak Point One pre http://listeninn.com/Pictures-Used/U...-Stereo-10.jpg. Here are some brown ones in an RCA LMI-32216A http://www.saturn-sound.com/images%2...ing%20side.jpg. Here are some 'orrible 'unts (her words ) in Kat Manton's Pamphonic 1004 https://www.vintage-radio.net/forum/...3&d=1277245073. Rogers seem to have resisted them though, using the impeccable Mullard mustards instead, and Radford stuck largely with Wima for their film capacitors.

Cheers,

GJ
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