Pye Hybrid CTV stock faults - UK Vintage Radio Repair and Restoration Discussion Forum

Mike Phelan · 27th Sep 2004, 8:27 am

In the distant past, it was suggested that we started this topic, so here goes:
Apologies for lack of component numbers - no manual!

Weak sync - contrast pot gone high
Weak or no line sync - 47k 2w feeding pulses to flywheel diodes burnt up
Line osc stopped - 100k in series with hold control o/c
Intercarrier buzz - adjust slope detector coil
Wavy horizontal lines (wired LOP type) - solder earth lead to line osc can (yes you can!)
Intermittent chroma - polystyrene caps (2 x 4700pf?) in ref osc
PCL84s overheating - change grid leaks from 2m2 to 680k

More when I get time!

Hybrid tellies · 27th Sep 2004, 9:53 pm

A few more.
Flyback lines: VT28 BC147 blanking transistor, in cathode feed of luminance output valve, short cct.
Colour casting effect across screen: R390-392 12K anode load resisters to CDA amps open circuit.
Line striations on left hand side of screen: 1.5K Resistor across line linearity coil open circuit.
Picture looks ok but frequent failure of HT rectifier,R306 and PL509 line output valve: Shorted turns with burn mark on EHT overwind.
No Picture with smoke pouring from back of set. C224 short circuit placing boost line across R227 (100K)
Intermittent line oscilator slow start. C210 4 uf electrolytic off the wiper of line hold control dried out, sometimes goes leaky as well.. We always changed out the 100k feed resistor R210.
Thats all that I can recall. Somebody elses turn to recall the many faults that afflicted this very troubled colour chassis :

dazzlevision · 28th Sep 2004, 10:00 pm

There is a 4.7MOhm on the IF panel which biases the sync separator transistor - goes o/c, causing weak sync.

The " pincushion amplitude " pot on the convergence panel goes o/c causing poor geometry.

The " sit up " pot on the frame panel goes intermittent, causing flyback lines (+ teletext twinklies) and poor top vertical linearity.

On the 697, the LOPTx tended to burn out, due to inadequate insulation/clearances on the EHT tripler winding. Later LOPTx had a white plastic ring on the core, to stop this.

Dazzlevision

27th Sep 2004, 8:27 am	#1
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,616	Pye Hybrid CTV stock faults In the distant past, it was suggested that we started this topic, so here goes: Apologies for lack of component numbers - no manual! Weak sync - contrast pot gone high Weak or no line sync - 47k 2w feeding pulses to flywheel diodes burnt up Line osc stopped - 100k in series with hold control o/c Intercarrier buzz - adjust slope detector coil Wavy horizontal lines (wired LOP type) - solder earth lead to line osc can (yes you can!) Intermittent chroma - polystyrene caps (2 x 4700pf?) in ref osc PCL84s overheating - change grid leaks from 2m2 to 680k More when I get time! __________________ Mike.

27th Sep 2004, 9:53 pm	#2
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,977	Re: Stock faults - Pye 691 and derivatives A few more. Flyback lines: VT28 BC147 blanking transistor, in cathode feed of luminance output valve, short cct. Colour casting effect across screen: R390-392 12K anode load resisters to CDA amps open circuit. Line striations on left hand side of screen: 1.5K Resistor across line linearity coil open circuit. Picture looks ok but frequent failure of HT rectifier,R306 and PL509 line output valve: Shorted turns with burn mark on EHT overwind. No Picture with smoke pouring from back of set. C224 short circuit placing boost line across R227 (100K) Intermittent line oscilator slow start. C210 4 uf electrolytic off the wiper of line hold control dried out, sometimes goes leaky as well.. We always changed out the 100k feed resistor R210. Thats all that I can recall. Somebody elses turn to recall the many faults that afflicted this very troubled colour chassis : __________________ Simon BVWS member

28th Sep 2004, 10:00 pm	#3
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,713	Re: Stock faults - Pye 691 and derivatives There is a 4.7MOhm on the IF panel which biases the sync separator transistor - goes o/c, causing weak sync. The " pincushion amplitude " pot on the convergence panel goes o/c causing poor geometry. The " sit up " pot on the frame panel goes intermittent, causing flyback lines (+ teletext twinklies) and poor top vertical linearity. On the 697, the LOPTx tended to burn out, due to inadequate insulation/clearances on the EHT tripler winding. Later LOPTx had a white plastic ring on the core, to stop this. Dazzlevision