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-   -   Pye hybrid colour stock faults (https://www.vintage-radio.net/forum/showthread.php?t=18011)

Mike Phelan 17th Feb 2004 9:51 am

Pye hybrid colour stock faults
 
Right - here are a few to start the ball rolling.

Hybrid Pye colour 691/693/697 - sorry no component numbers.

Weak line and frame sync - contrast pot gone high
Sound distortion and buzz - adjust slope detector coil on IF strip
No line sync - 47k 2w feeding line pulses to f/w sync burnt up
Line osc stopped or wrong speed - 100k/120k in series with hold control O/c
Reduced width - valves OK, HT OK - shift choke on LOPTx
Ripples on lines - metal LOP chassis type. Solder (yes!) earth lead to line osc coil can
PCL84s overheating and low anode volts. Replace valves and reduce grid leak resistors to 680k
Reference osc stopped or intermittent - 2 x 4700pf
polystyrene caps

Hybrid tellies 18th Feb 2004 12:23 am

Re: Television Stock Faults
 
Well here's my contribution.

In addition to what has already been mentioned, here are a few more.
Colour casting effects across screen. Either one of R390, R391 & R392 o/c. All are 12k wirewound resisters on CDA board feeding the R-Y G-Y & B-Y amplifiers.
Flyback lines due to VT28 (BC147) short cct. Generally due to poor condition cda board.
Lazy line oscillator ie can take 5 mins or more to start causing considerable over heating in line output stage. Fault often cleared by replacing C210 (4uf) electrolytic off wiper of line hold together with feed resister R210 (100K)
No picture with smoke and overheating line output stage,eventually blowing the mains fuse. C224 (0.1uf) s/c burning out feed resister R227 (100K). Both components on boost line feed to the A1 controls.
Line striations on left hand side of picture due to R228 (1.5k) connected across the line lin coil o/c.


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