Thread: Pye v4
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Old 10th May 2010, 4:13 pm   #504
DangerMan
Heptode
 
Join Date: Jul 2009
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 719
Default Re: Pye v4

I'd agree Chris, the linearity isn't bad.
To be honest, I don't think I've ever seen a V4/VT4 with really good horizontal linearity and I've attached a snap of mine which was at an early stage of resuscitation. The line linearity coil on my set is quite badly fried and isn't adjustable.. perhaps that's the way they all go (?). I haven't done any work on mine since this photo was taken, so I don't know.
The black level gated AGC acts only on one valve, V4, and unlike later sets it has quite a restricted range, meaning that the sensitivity control must be set to put the signal level at this valve within the range that can be handled by the AGC system.
If any stage of the set in front of this one goes into overload there's nothing the contrast control can do about it, hence the separate sensitivity adjustment at the front end.
As has been mentioned, the line sync has to be set up well for the AGC to work properly.
I'd say Well Done!

Pete

PS Before I get shot to pieces, I'm not saying a V4 with good linearity doesn't exist, only that I've never seen one !!
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