I’m back, CP90 playing up again - UK Vintage Radio Repair and Restoration Discussion Forum

Tvnoob007 · 21st Jun 2020, 4:40 pm

After fitting a new LOPT to my CP90 PYE 15” all was well for about 4 hrs total run time spread over the last couple of months.

Then on a 2hr run yesterday it decided to do this:

Tvnoob007 · 21st Jun 2020, 4:48 pm

The screen is jittering as if the frame is going to collapse into the middle. Near the top is what looks like an over trace, maybe fly back.

I’m sure it did this years ago, but I can’t remember if it was just before the LOPT died or maybe I have turned the screen adjustment to high on the LOPT when I set it up and now it’s dying?

The supplier did supply a Philips LOPT, that looked like old new stock, rather than the modern copy that I ordered. Could it be a duff LOPT again? Or is my board eating LOPT’s?

Red to black · 21st Jun 2020, 5:16 pm

The CP90 was a fairly well behaved chassis, the stock faults were predictable and reasonably easily repaired.
Yes the lopt was a weak point as were several other items, the lopts normally survived a lot longer than the then 12 months guarantee though.
The chassis were on the whole fairly reliable and not really (probably a lot better) any worse than some of their counterparts by other makers of the time.

Tvnoob007 · 21st Jun 2020, 5:24 pm

Any ideas what’s causing the partial frame collapse?

samjmann · 21st Jun 2020, 5:37 pm

If you've access to a scope the line flyback waveform is the thing to look at.
Has the line output transistor started to get unusually warm? I had a 15'' CP90 for years, apart from the battery it never failed. Working at a Philips agency I did see quite a few. What's been the sets history? Is there lot's of replaced parts from previous job's.

If you've got the wrong transformer, if it's totally wrong you're normally rewarded with a big bang.

At least you haven't got the CP110 power unit to fix...

Have a look at the boost rail to make sure you have 163V. The field is a bit unusual on these in that it runs on the 95V HT. As the boost may now be high due to the new Tx, it's worth checking the supply for voltage and ripple.

SJM.

Red to black · 21st Jun 2020, 5:51 pm

As I had a quick look at my paper diagram and as far as I can remember off hand R3623 8.2 ohms is common to both the field output stage and the 163V feed for the RGB output stages, this would tie in with both of your current symptoms.

Check around this area and the associated Electrolytic cap C2623 a 22uf 250V as a start.
I am not saying this is your fault, but I have ringed both of those components in my manual.

edit: Great minds SJM

Tvnoob007 · 21st Jun 2020, 9:52 pm

Well this is weird I’m not even sure what fixed it. I reflowed the LOPT and did notice the extra pin had pushed the track up slightly, because when I first installed it I didn’t have it sat down far enough, i then removed the solder on the other pins but forgot that one. So when I pushed the LOPT to clip it in it lifted that pad by about 0.5mm.

I checked the 163v was ok. 95v ok. 19v ok.

I then tried adjusting the frame height a bit and when I looked at the tv it was ok.

Maybe a dry pot?

21st Jun 2020, 4:40 pm	#1
Tvnoob007 Tetrode Join Date: Apr 2020 Location: Boston, Lincolnshire, UK. Posts: 58	I’m back, CP90 playing up again After fitting a new LOPT to my CP90 PYE 15” all was well for about 4 hrs total run time spread over the last couple of months. Then on a 2hr run yesterday it decided to do this: Attached Thumbnails

21st Jun 2020, 4:48 pm	#2
Tvnoob007 Tetrode Join Date: Apr 2020 Location: Boston, Lincolnshire, UK. Posts: 58	Re: I’m back, CP90 playing up again The screen is jittering as if the frame is going to collapse into the middle. Near the top is what looks like an over trace, maybe fly back. I’m sure it did this years ago, but I can’t remember if it was just before the LOPT died or maybe I have turned the screen adjustment to high on the LOPT when I set it up and now it’s dying? The supplier did supply a Philips LOPT, that looked like old new stock, rather than the modern copy that I ordered. Could it be a duff LOPT again? Or is my board eating LOPT’s?

21st Jun 2020, 5:16 pm	#3
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,475	Re: I’m back, CP90 playing up again The CP90 was a fairly well behaved chassis, the stock faults were predictable and reasonably easily repaired. Yes the lopt was a weak point as were several other items, the lopts normally survived a lot longer than the then 12 months guarantee though. The chassis were on the whole fairly reliable and not really (probably a lot better) any worse than some of their counterparts by other makers of the time. __________________ I don't suffer from Insanity. I enjoy every minute of it.

21st Jun 2020, 5:24 pm	#4
Tvnoob007 Tetrode Join Date: Apr 2020 Location: Boston, Lincolnshire, UK. Posts: 58	Re: I’m back, CP90 playing up again Any ideas what’s causing the partial frame collapse?

21st Jun 2020, 5:37 pm	#5
samjmann Heptode Join Date: Feb 2014 Location: Nottingham, UK. Posts: 648	Re: I’m back, CP90 playing up again If you've access to a scope the line flyback waveform is the thing to look at. Has the line output transistor started to get unusually warm? I had a 15'' CP90 for years, apart from the battery it never failed. Working at a Philips agency I did see quite a few. What's been the sets history? Is there lot's of replaced parts from previous job's. If you've got the wrong transformer, if it's totally wrong you're normally rewarded with a big bang. At least you haven't got the CP110 power unit to fix... Have a look at the boost rail to make sure you have 163V. The field is a bit unusual on these in that it runs on the 95V HT. As the boost may now be high due to the new Tx, it's worth checking the supply for voltage and ripple. SJM. Last edited by samjmann; 21st Jun 2020 at 5:50 pm. Reason: Added sentence.

21st Jun 2020, 5:51 pm	#6
Red to black Nonode Join Date: Mar 2010 Location: Sunderland, Tyne and Wear, UK. Posts: 2,475	Re: I’m back, CP90 playing up again As I had a quick look at my paper diagram and as far as I can remember off hand R3623 8.2 ohms is common to both the field output stage and the 163V feed for the RGB output stages, this would tie in with both of your current symptoms. Check around this area and the associated Electrolytic cap C2623 a 22uf 250V as a start. I am not saying this is your fault, but I have ringed both of those components in my manual. edit: Great minds SJM __________________ I don't suffer from Insanity. I enjoy every minute of it.

21st Jun 2020, 9:52 pm	#7
Tvnoob007 Tetrode Join Date: Apr 2020 Location: Boston, Lincolnshire, UK. Posts: 58	Re: I’m back, CP90 playing up again Well this is weird I’m not even sure what fixed it. I reflowed the LOPT and did notice the extra pin had pushed the track up slightly, because when I first installed it I didn’t have it sat down far enough, i then removed the solder on the other pins but forgot that one. So when I pushed the LOPT to clip it in it lifted that pad by about 0.5mm. I checked the 163v was ok. 95v ok. 19v ok. I then tried adjusting the frame height a bit and when I looked at the tv it was ok. Maybe a dry pot?