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Old 12th Nov 2010, 8:27 pm   #27
dominicbeesley
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Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
Default Re: VT4 horz scan stage conundrum

Hello lads,

Just popped into the workshop to do some more tests...

Linearity Coil
A day on the radiator made no difference.
Removing the paxolin core and heat-shrink surround made a small positive difference
Adding a shorted turn made no obvious difference
The coil is wave wound so not so easy for me to reconstruct.

Width Coil
Inductance range is roughly 3-15mH and has already been rewound, this is pile wound

At 3mH it tunes against a 1uF cap at 2700c/s and has a Q of 4.5,
At 15mH it tunes against a 1uF cap at 1300Hz and has a Q > 10

Adding a shorted turn reduced the level of the wave but didn't affect the Q by much (or at least not with my rough setup).

LOPT
As I'd got everything disconnected to the LOPT I did a ring test - 1kHz wave fed into one end of the overwind and scope probe on the other. Pictures with and without the EY51's heater in place....

Questions

Is the linearity coil duff or do I need to do more measurements?
Does that look like the LOPT is ok?
Would I be better off retesting Q etc at a higher frequency?
I've been using 22k as the series resistance, is this too low?

Cheers

Dom

PS: Off for a lie down I've got a terrible cold and feel so bad I don't even want to go to the pub...
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