It is currently Sat May 26, 2018 3:33 am

KB Royal Star

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Fri Dec 11, 2015 11:09 am

Derren wrote:Hi Till,

If am not mistaken your friend on the other forum said that most customers would not notice the fault even when it was pointed out to them? Is that the case, what sort of picture would result with it in this state?

Hi Derren
That's right, back in the sixties viewers would tolerate faults such as bad interlace. In fact even when the prominent line structure was pointed out to them the answer was often: what are you talking about?.

As an attempt to solve the problem I'll try a simple snubber capacitor and resistor across the frame scan coils.
I'll try this out later today.

Till Eulenspiegel.

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: KB Royal Star

Post by nuvistor » Fri Dec 11, 2015 3:56 pm

Not directly to do with interlace but poor pictures in general.
Some customers would put up with very poor pictures, some due to indifference and some in poor reception areas had no choice.
They must have had enjoyment out of whatever reception they could have. I wonder sometimes with all this HD and 4K/8K whether the modern viewer gets any more enjoyment out of these, no doubt superb picture quality sets, than the old B/W 405 we had a few years ago.
Or perhaps it is me, not liking what content the TV channels now provide.
Thoughts and rant over. ttt:

Frank

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Fri Dec 11, 2015 4:54 pm

Do it properly and 405 line pictures can be stunning. But the interlace problem must be addressed.

Till Eulenspiegel.

 
Posts: 437
Joined: Fri Aug 26, 2011 10:45 am
Location: Gateshead

Re: KB Royal Star

Post by Focus Diode » Fri Dec 11, 2015 5:28 pm

nuvistor wrote:Not directly to do with interlace but poor pictures in general.
Some customers would put up with very poor pictures, some due to indifference and some in poor reception areas had no choice.


This subject is worthy of its own thread. Amazing what some tolerated in times gone by.
Another restoration job beyond first class from Till.
Cheers
Brian

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: KB Royal Star

Post by nuvistor » Fri Dec 11, 2015 5:29 pm

Yes, appreciate it needs fixing.
I did got lots of enjoyment out of good 405 pictures and as you say they could be superb.
It will be interesting to see what the ultimate fix is for the interlace fault.

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Fri Dec 11, 2015 6:07 pm

As Brian suggested it will be idea to introduce a new topic about the appalling pictures viewers used to watch in the old days.
That's why I used to supply an aerial with the sets I rented out in order to get the best possible pictures from the 405 line sets. Even more important when 625 came along. The idea was to give a complete service.

Till Eulenspiegel.

 
Posts: 79
Joined: Wed Apr 08, 2015 2:52 pm
Location: Newcastle Upon Tyne

Re: KB Royal Star

Post by Derren » Fri Dec 11, 2015 6:13 pm

This set has had a variety of annoying and hard to find faults (for me at least!), but am sure that tube is capable of a superb picture, it would be great to see it finally settle down and behave as it should! On the wider point about picture quality it occurred to me recently, especially when watching the likes of the Dynatron and the Baird M640, that only now with the advent of affordable converters, well restored sets and indeed well restored films on DVD, are we perhaps for the first time beginning to see what 405 line sets are capable of. Am sure the signal/source material quality/reception was nothing like as good back then!

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Mon Dec 14, 2015 6:56 pm

The scope was connected up to the frame scan coils to determine if there is any line timebase waveform present at that point in the circuit. None, just a perfect sawtooth waveform at frame frequency. Nevertheless, the interlace fault could still be the scanning coils. As mentioned earlier in this discussion the problem was well known in certain Kolster-Brandes models which employed the 110 degree CRT.
I'm entirely satisfied that the interlace filter circuit is working properly.
I do know of another owner of a KB set that employs a 110 degree CRT. The set was serviced by me over four years ago and if there had been any problems with the interlace the effect would certainly been noticeable because the set is a 21" model. The QF80 "Majestic".

Here's and idea. Why not switch on the equalising pulses and see what happens?

Till Eulenspiegel.

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Mon Dec 14, 2015 7:02 pm

Switched on the Aurora EQ pulses. No improvement, the interlace is as bad as ever!

Till Eulenspiegel.

 
Posts: 3712
Joined: Sun Feb 12, 2012 7:43 pm
Location: North Hykeham, Lincolnshire and Ilford, Essex (but not for much longer ...!)

Re: KB Royal Star

Post by Terrykc » Tue Dec 15, 2015 11:04 am

In this post you showed a very clear picture of the field sync  pulse.  

Can you display the field sync with the 'scope triggered at line rate?

This should then show two overlapped field pulses with a half line difference between them.

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Tue Dec 15, 2015 2:24 pm

The scope traces clearly show the half line off-set. The oscilloscope was triggered by the frame sync pulse which is present at the anode of the clipper triode. The frame sync pulse maintains it's shape irrespective of which picture field is received. I'm absolutely sure that the triggering of the frame oscillator is precise enough for normal interlacing under normal circumstances.

Till Eulenspiegel
Attachments
000_0193.jpg
000_0193.jpg (115.74 KiB) Viewed 1509 times
000_0194.jpg
000_0194.jpg (118.77 KiB) Viewed 1509 times

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Tue Dec 15, 2015 4:30 pm

Just to confirm that there are no funnies going on in the frame output stage, another test to determine the relationship between the line and frame syncs the scope was triggered from the frame blanking pulse which is present at the slider of the brightness control.
Again, like the previous test procedure, I find the picture field by field half line sync off-set is correct.

It's got be those scan coils. An old KB problem has come back to haunt us.

Till Eulenspiegel.

 
Posts: 489
Joined: Tue Mar 24, 2015 12:01 am
Location: Wigan

Re: KB Royal Star

Post by nuvistor » Tue Dec 15, 2015 6:02 pm

And chance of a that a set of scan coils from another make of TV will work?

 
Posts: 79
Joined: Wed Apr 08, 2015 2:52 pm
Location: Newcastle Upon Tyne

Re: KB Royal Star

Post by Derren » Tue Dec 15, 2015 6:48 pm

If this is a real problem that you can't solve D. then it could be left as is if you are busy with other things in the run up to Christmas, as you say many people watched the picture like this, it couldn't have been that bad. I suppose you could say this type of pic is even part of TV history :) Any chance of uploading an image of a pic on the screen in its current state? At least you have cured the awful frame and linearity problems.

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Tue Dec 15, 2015 9:12 pm

nuvistor wrote:And chance of a that a set of scan coils from another make of TV will work?

Hi Nuvistor,
That's the problem, finding the correct scan coils for the QVP20. I believe that the chassis mounted scan coil assembly was a special one and designed specifically for the set.

Hi Derren,
The poor picture interlace apart, the definition is excellent and the timebases are stable. Once set, the line and frame hold controls rarely need any adjustment.
Here's an idea? Reinstall the chassis into the cabinet, place the set on display in the shop to assess what members of the public think of the pictures. I'd be surprised if anyone makes a comment about the prominent line structure.

I'll reintroduce the Royal Star topic on the other forum.

Till Eulenspiegel.

 
Posts: 79
Joined: Wed Apr 08, 2015 2:52 pm
Location: Newcastle Upon Tyne

Re: KB Royal Star

Post by Derren » Tue Dec 15, 2015 11:16 pm

Good idea. Mind you I already think I would approve as I do quite like to see the line structure myself! Sometimes this type of image is used in modern music videos especially when trying to depict something old, they must be assuming all old telly pictures once looked like this :)

 
Posts: 2839
Joined: Tue Jul 26, 2011 5:30 pm
Location: Gateshead

Re: KB Royal Star

Post by Till Eulenspiegel » Fri Dec 18, 2015 6:29 pm

I reckon the Royal Star resto job can be signed off now. Pity about the poor interlace though.

Till Eulenspiegel.
Attachments
000_0199.jpg

Previous

Return to Black & White Television



Who is online

Users browsing this forum: No registered users and 4 guests