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Old 18th Feb 2004, 12:23 am   #2
Join Date: Nov 2003
Location: Chelmsford, Essex, UK.
Posts: 121
Default BRC 1500 stock faults

Poor sync on BRC/Thorn 1500 series chassis was usually caused by failure of R44 (sync. separator screen feed resistor); the cure was to replace this with a component of at least 1 watt rating.

It's half Lombard Street to a china orange (as my Dad used to say) that any 1500 still extant will have had this done long ago! I guess this could well be true for many stock faults - but it's still good to know about them.

Somebody has already mentioned the no sync fault so here are a few more.
Weak video with lots of streaking: R40, R41 video output stage load resisters gone high or o/c. Both can be changed out using 1 x 3.3k and 1x 3.9k 1w resisters. Same symptoms can also be caused by electrolytic cap C37 (64uf) which feed video to base of video output transistor.
For poor frame linearity and frame jitter change out R101 & R102 both 18k 1w resisters. These are fitted across the primary winding of frame output transformer.
Frame cramp on bottom of picture with poor frame hold. C89 (1uf) dried out. This capacitor smooths the boost line feed to the frame oscillator.
David F. Symes
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