1500 line tearing habit & other faults - UK Vintage Radio Repair and Restoration Discussion Forum

johnmarshmanagain · 21st Feb 2007, 12:40 am

Hi all,
Is there a 1500 stock fault associated with intermittent line tearing? The lines are not only displaced, but also black. Problem progressively worse as the contrast is advanced; have tried a fresh 30FL2 sync sep to no avail.
ta
j

Steve_P · 21st Feb 2007, 12:59 am

First of all, have you been watching DVD/Videos here? Try it off-air! However, this is probably not the sync separator, but could be before this. Check round the video amps, and also try knocking the Local/Distant control off a bit.

Cheers,

Steve P

Mick Mearman · 21st Feb 2007, 11:55 pm

Hello
Have you checked the CRT earthing spring is still in place?
Mick

johnmarshmanagain · 22nd Feb 2007, 12:19 am

hi all
- mmm, well cranking up the local/distant and cranking down the contrast has certainly calmed it down tolerably - guess is this cos any spikes are less apparent relative to the signal....
- as regards the spring will have a dekko, ta for that one
- it's a crabby old set that'd been cannibalised but it's amused me pulling it together....
j

Steve_P · 22nd Feb 2007, 12:34 am

If it's been cannibalised, a mortal sin in my book, then look closely at all parts and holes! There might well be something missing or out of alignment. If the earthing spring is in there and correct, look at the set closely.

Cheers,

Steve P

Steve_P · 22nd Feb 2007, 1:11 am

Oh yes - looking at the circuit and thinking again:

Checks - is the Line Hold control OK or very touchy? Check W3, W4, C43, C44, C51 and VT10. If you have a scope, check the Line and Frame sync pulses.

Cheers,

Steve P

Mike Phelan · 22nd Feb 2007, 9:05 am

If one of Steve's Cs is the time constant for the flywheel sync, it will cause cogging if O/C.

Heatercathodeshort · 22nd Feb 2007, 9:33 am

Hello,
A very common fault causing this fault is the 64uf video coupling electrolytic.
It can be replaced with a 100uf. That is a first port of call to start with.
Regards
John.

Steve_P · 22nd Feb 2007, 10:41 am

That's C37, on the base of VT9.

Cheers,

Steve P

Focus Diode · 23rd Feb 2007, 12:30 pm

The late great George Wilding once commented on a similar fault caused by the EHT tray on one of these sets. This is another possibility seeing that adjusting the contrast has some effect.

Brian R

dazzlevision · 23rd Feb 2007, 4:01 pm

Hi,

Concerning the possibility of a faulty tripler/doubler, this would only apply if the "open" type was fitted, where the selenium rectifier "sticks" can be seen through holes in the two-part plastic case. It was usually accompanied by the smell of rotten eggs and could usually be made to come and go by varying the brightness control.

If the tripler or doubler is of the potted/sealed variety, it almost certainly uses silicon rectifiers.

Regards,

dazzlevision

Top Cap · 23rd Feb 2007, 5:45 pm

Gee it's been years since I worked on these and the grey matter has since become like a black hole. Yes I do remember C37 but was there a 1uF HV electrolytic somewhere that also did this? I think it was C89 but maybe that caused another fault.
Yep tripler changing has been known to cure a similar problem that occurred mainly with varying the brilliance/crt beam current. I remember getting a wavy vertical white line down one side, cured by placing an earthed loop of copper wire round the PL504 and adjusting it up or down for best removal of the jagged line. Those were the days!

Mike Phelan · 23rd Feb 2007, 5:57 pm

Quote:

Originally Posted by Top Cap

I remember getting a wavy vertical white line down one side, cured by placing an earthed loop of copper wire round the PL504 and adjusting it up or down for best removal of the jagged line. Those were the days!

The Barkhausen-Kurz effect. In the PL81 days, you could get little magnets to put around the valve; looked like an ion trap. It would stop this oscillation.
In the trade, called "Barkhausen's Curse"

FERNSEH · 23rd Feb 2007, 6:00 pm

Quote:

Originally Posted by Top Cap

Yes I do remember C37 but was there a 1uF HV electrolytic somewhere that also did this? I think it was C89 but maybe that caused another fault.

Was that capacitor the screen grid decoupler of the PL504?

DFWB.

ALANS ANITAS · 23rd Feb 2007, 7:51 pm

An article in "Television" for February 1984, Malcolm Burrell suggests the screen feed resistor for the sync separator, R44 should be replaced by a 1 watt component. C53 in the line oscillator charging circuit can go leaky, and cause line tearing, perhaps intermittant.

ALAN

Focus Diode · 24th Feb 2007, 12:33 pm

Quote:

Originally Posted by dazzlevision

Concerning the possibility of a faulty tripler/doubler, this would only apply if the "open" type was fitted, where the selenium rectifier "sticks" can be seen through holes in the two-part plastic case. It was usually accompanied by the smell of rotten eggs and could usually be made to come and go by varying the brightness control.

Absolutely true this Dazzlevision. In George's case there was no obvious visual problems or aroma usually associated with a defective tripler. The ragged edges virtually disappeared when the brightness was set very low.

Brian R

johnmarshmanagain · 23rd Mar 2007, 1:17 am

hi fellas
Yes, there is increasing raggedness as the brightness is advanced, and it's very bad in the limit, so that the picture's torn to pieces.

However, when the brightness is lower (normal) there's still this wretched niggly shaking of every line in the picture; not random but consistent, the start of each line is noticeably wobbling by a couple of mm.

Have pretty much tried all the suggestions previously listed; the anode of the sync sep is at 96v and the screen at 59v - imagine this is correct but service data is silent on the subject of voltages!

The attached piccie is of the waveform at the base of VT10 (the dc amplifier feeding the line osc) - looks a mess to me - is it a clue?
Timebase on scope 20us approx, and peak to peak is a volt ish

Steve_P · 23rd Mar 2007, 1:36 am

The triplers plug on to the side of the LOPT on these sets. There are 2 types - 3 Stick and 5 Stick. I reckon that if you whip it off, clean the contacts and put it back, it'll either work or it wont.

Remember the usual things about EHT, and while it's off, put a picture up so we know which one it is. In case you need one.

If you're not sure what to do or high voltages scare you (like they should with me but never have!) then PM me and you can bring it up here.

Cheers,

Steve P

johnmarshmanagain · 24th Mar 2007, 1:45 am

Incidentally, can anyone kindly advise on lack of picture width ? HT at top of R64 is 203v tonight, so maybe not bad (book says 190-odd). poss bad lopt I suppose - there must have been summat that caused it to start to be cannibalised 1? Ta J

Mikey405 · 24th Mar 2007, 8:36 am

The PL504 is always the first suspect for lack of width. Who knows, it may even cure your line-tearing.

From Mike.

21st Feb 2007, 12:40 am	#1
johnmarshmanagain Pentode Join Date: Aug 2005 Location: Northwich, Cheshire, UK. Posts: 206	1500 line tearing habit & other faults Hi all, Is there a 1500 stock fault associated with intermittent line tearing? The lines are not only displaced, but also black. Problem progressively worse as the contrast is advanced; have tried a fresh 30FL2 sync sep to no avail. ta j Last edited by Mike Phelan; 28th Dec 2007 at 10:39 am. Reason: Readability

21st Feb 2007, 12:59 am	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: 1500 line tearing habit First of all, have you been watching DVD/Videos here? Try it off-air! However, this is probably not the sync separator, but could be before this. Check round the video amps, and also try knocking the Local/Distant control off a bit. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

21st Feb 2007, 11:55 pm	#3
Mick Mearman Retired Dormant Member Join Date: Feb 2005 Location: Kingswinford, West Midlands Posts: 0	Re: 1500 line tearing habit Hello Have you checked the CRT earthing spring is still in place? Mick

22nd Feb 2007, 12:19 am	#4
johnmarshmanagain Pentode Join Date: Aug 2005 Location: Northwich, Cheshire, UK. Posts: 206	Re: 1500 line tearing habit hi all - mmm, well cranking up the local/distant and cranking down the contrast has certainly calmed it down tolerably - guess is this cos any spikes are less apparent relative to the signal.... - as regards the spring will have a dekko, ta for that one - it's a crabby old set that'd been cannibalised but it's amused me pulling it together.... j

22nd Feb 2007, 12:34 am	#5
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: 1500 line tearing habit If it's been cannibalised, a mortal sin in my book, then look closely at all parts and holes! There might well be something missing or out of alignment. If the earthing spring is in there and correct, look at the set closely. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

22nd Feb 2007, 1:11 am	#6
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: 1500 line tearing habit Oh yes - looking at the circuit and thinking again: Checks - is the Line Hold control OK or very touchy? Check W3, W4, C43, C44, C51 and VT10. If you have a scope, check the Line and Frame sync pulses. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

22nd Feb 2007, 9:05 am	#7
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: 1500 line tearing habit If one of Steve's Cs is the time constant for the flywheel sync, it will cause cogging if O/C. __________________ Mike.

22nd Feb 2007, 9:33 am	#8
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: 1500 line tearing habit Hello, A very common fault causing this fault is the 64uf video coupling electrolytic. It can be replaced with a 100uf. That is a first port of call to start with. Regards John.

22nd Feb 2007, 10:41 am	#9
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: 1500 line tearing habit That's C37, on the base of VT9. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

23rd Feb 2007, 12:30 pm	#10
Focus Diode Octode Join Date: Jan 2006 Location: Borough of Gateshead, UK. Posts: 1,420	Re: 1500 line tearing habit The late great George Wilding once commented on a similar fault caused by the EHT tray on one of these sets. This is another possibility seeing that adjusting the contrast has some effect. Brian R

23rd Feb 2007, 4:01 pm	#11
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: 1500 line tearing habit Hi, Concerning the possibility of a faulty tripler/doubler, this would only apply if the "open" type was fitted, where the selenium rectifier "sticks" can be seen through holes in the two-part plastic case. It was usually accompanied by the smell of rotten eggs and could usually be made to come and go by varying the brightness control. If the tripler or doubler is of the potted/sealed variety, it almost certainly uses silicon rectifiers. Regards, dazzlevision

23rd Feb 2007, 5:45 pm	#12
Top Cap Octode Join Date: Mar 2006 Location: Watford, Hertfordshire, UK. Posts: 1,270	Re: 1500 line tearing habit Gee it's been years since I worked on these and the grey matter has since become like a black hole. Yes I do remember C37 but was there a 1uF HV electrolytic somewhere that also did this? I think it was C89 but maybe that caused another fault. Yep tripler changing has been known to cure a similar problem that occurred mainly with varying the brilliance/crt beam current. I remember getting a wavy vertical white line down one side, cured by placing an earthed loop of copper wire round the PL504 and adjusting it up or down for best removal of the jagged line. Those were the days! __________________ Whether the Top Cap is Grid or Anode - touching it will give you a buzz either way!

23rd Feb 2007, 7:51 pm	#15
ALANS ANITAS Rest in Peace Join Date: Jun 2006 Location: North West Northamptonshire, UK. Posts: 346	Re: 1500 line tearing habit An article in "Television" for February 1984, Malcolm Burrell suggests the screen feed resistor for the sync separator, R44 should be replaced by a 1 watt component. C53 in the line oscillator charging circuit can go leaky, and cause line tearing, perhaps intermittant. ALAN

23rd Mar 2007, 1:17 am	#17
johnmarshmanagain Pentode Join Date: Aug 2005 Location: Northwich, Cheshire, UK. Posts: 206	Re: 1500 line tearing habit hi fellas Yes, there is increasing raggedness as the brightness is advanced, and it's very bad in the limit, so that the picture's torn to pieces. However, when the brightness is lower (normal) there's still this wretched niggly shaking of every line in the picture; not random but consistent, the start of each line is noticeably wobbling by a couple of mm. Have pretty much tried all the suggestions previously listed; the anode of the sync sep is at 96v and the screen at 59v - imagine this is correct but service data is silent on the subject of voltages! The attached piccie is of the waveform at the base of VT10 (the dc amplifier feeding the line osc) - looks a mess to me - is it a clue? Timebase on scope 20us approx, and peak to peak is a volt ish Attached Thumbnails Last edited by Mike Phelan; 28th Dec 2007 at 10:47 am. Reason: S, P and found shift key

23rd Mar 2007, 1:36 am	#18
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: 1500 line tearing habit The triplers plug on to the side of the LOPT on these sets. There are 2 types - 3 Stick and 5 Stick. I reckon that if you whip it off, clean the contacts and put it back, it'll either work or it wont. Remember the usual things about EHT, and while it's off, put a picture up so we know which one it is. In case you need one. If you're not sure what to do or high voltages scare you (like they should with me but never have!) then PM me and you can bring it up here. Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

24th Mar 2007, 1:45 am	#19
johnmarshmanagain Pentode Join Date: Aug 2005 Location: Northwich, Cheshire, UK. Posts: 206	Re: 1500 line tearing habit Incidentally, can anyone kindly advise on lack of picture width ? HT at top of R64 is 203v tonight, so maybe not bad (book says 190-odd). poss bad lopt I suppose - there must have been summat that caused it to start to be cannibalised 1? Ta J

24th Mar 2007, 8:36 am	#20
Mikey405 Octode Join Date: Jul 2006 Location: Solihull, West Midlands and Beaford, Devon Posts: 1,626	Re: 1500 line tearing habit The PL504 is always the first suspect for lack of width. Who knows, it may even cure your line-tearing. From Mike. __________________ G7TRF