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FERNSEH · 25th Apr 2018, 10:36 am

Hi Nick,
Somehow we have to generate the keying pulse for the vision frame gated vision AGC system. This is easy if modern semiconductors are employed but the rules must be followed which means only the components and technology of those times must be adhered to.
There is an explanation about the workings of the vision AGC system in the Ultra V17-60 in volume two of the Spreadbury book "Television Receiver Servicing".
The Ultra V17-60 is unusual in having vision AGC supplied to the 30C1 tuner mixer valve. Four stages amplifying stages are controlled by the vision AGC system, the 30L1 RF amplifier, the 30C1 mixer and the two common vision and sound IF amplifiers.
In the Ultra V9-17 only the RF amplifier and common vision and sound IF amplifier are controlled by the vision AGC.

DFWB.

25th Apr 2018, 10:36 am	#14
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Frame gated AGC modifications Hi Nick, Somehow we have to generate the keying pulse for the vision frame gated vision AGC system. This is easy if modern semiconductors are employed but the rules must be followed which means only the components and technology of those times must be adhered to. There is an explanation about the workings of the vision AGC system in the Ultra V17-60 in volume two of the Spreadbury book "Television Receiver Servicing". The Ultra V17-60 is unusual in having vision AGC supplied to the 30C1 tuner mixer valve. Four stages amplifying stages are controlled by the vision AGC system, the 30L1 RF amplifier, the 30C1 mixer and the two common vision and sound IF amplifiers. In the Ultra V9-17 only the RF amplifier and common vision and sound IF amplifier are controlled by the vision AGC. DFWB.