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Old 1st Jul 2020, 11:20 am   #40
dazzlevision
Dekatron
 
Join Date: Sep 2003
Location: Near Swindon, North Wiltshire, UK.
Posts: 3,611
Default Re: Marconi 1400 birthday present

Quote:
Originally Posted by dazzlevision View Post
OK, if you are sure that all the critical capacitors have been replaced in the line output stage and you’ve tested and replaced where necessary, all the high value resistors, then I suggest:

Check for out of spec carbon composition resistors in the line blocking oscillator circuit: R70 39k.
Note that R70 changes to 33k in later production, "to cure line scan crushing". Worth changing to this value, even if the originally fitted 39k resistor is within spec - unlikely after 50 years!
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