Sony KV1320UB/ KV1300UB - EHT Regulation?
I have just restored both a KV1300 and a 1320UB (many thanks to members of this forum for parts help!)
On both these sets, the picture size /EHT regulation does not seem great.
At a reasonable to high Brightness/Contrast settings, the picture size increases and the raster crumples and the sides become bowed inwards. At low settings the geometry is very good. I remember I had a KV1320 many years ago with the same effect.
Is this normal for these early sets?
The picture quality otherwise is very good.
The KV1320UB is a Mk1 with the 3AT2 EHT rectifier and the Kv1300UB has a silicon rectifier. The results are the same on both sets. The emission of the 3AT2 seems good.
Just need to check before I go investigating a possible issue.
I don't know these sets but a suggestion is poor HT regulation, whether by design or a fault.
Sounds strange! I have 2 1330ub's here, and I can't say I've ever noticed the faults you mention on either of them. I'll fire them up in a bit and see if I can re-create the faults you describe.
I was told a while back that the BBC used these sets as field monitors, I wouldn't have thought they would use them if they did this.
Thanks for your replies chaps. yes its a bit strange. The HT is fine, steady at all brightness levels. I know some sets are like this up to a point. The brightness doesn't drop, just the raster shape changes at high brightness levels.
I will try to post some pics shortly of both low level and high level brightness to demonstrate this effect.
Ok here are 4 pictures,
2 from the KV1300 first with low contrast and second high contrast. The camera compensates for the brightness so the look similar and grainy but they are not.
The same for the second set, KV1320UB this time.
as can be seen, corrugated verticals actually on the KV1300 with some slight bowing with the higher setting.. the raster shape is not the best on this set, it seem the scan coils are out of shape!
the patterning is caused by the camera btw!
That is an odd one! Looks a bit like 'cogging'. I also notice the colours are different between the 2 sets?
Could they be affected by too high a signal level? Maybe try an attenuator. Does it also do it on another source, try playing a DVD through a modulator (unless that's where your test card is coming from!) or a pattern generator. I'm using Mikey405's downloadable test card DVD played on a DVD/VHS combo machine with it's own RF output.
I've tried to re-create the problem on my 2 KV-1330's, but all I got was the picture would expand a little bit between low and high settings of both the 'picture' and 'BRT' controls. The geometry didn't change, although the set in the pic on top already had trouble with the pincushion setting anyway. Neither of these sets have had any restoration! The bottom one is in a rather rough state though, and the colours are a bit off.
^ BRT=max, Picture=0
^ BRT=0, Picture=max
^ BRT=0, Picture=0
^ BRT=max, Picture=max
^ BRT=mid, Picture=mid.
as can be seen, corrugated verticals actually on the KV1300 with some slight bowing with the higher setting.
The deviation of the verticals is greatest when the horizontal detail is brightest, and vice versa.
That is when the CRT beam is at the highest and lowest current, respectively.
Does this set have a beam current limiter? One that would lower the EHT if the beam current is too high?
Lowering the EHT would increase the scan factor, causing the raster to bloom.
Does this set have a black level clamp?
Can you measure the beam current with a scope ( a meter won't do, it would respond too slowly and not catch the peaks)?
Where is that pattern signal coming from? My PTV (Philips PM5534) generator doesn't have the graphic and text in the upper box, which looks more than peak white (100 IRE) in your PIX.
Can you check the base-band video from the generator on a scope to see if it's too high on those lines with the white box?
Thanks for the replies for this problem. it could be as Ford Anglia says the drive from the Pattern Generator is too high ( Promax GV698), howver the RF modulator shows no sign of peak white crushing.
These sets do have a black level clamp and should have a beam limiter, it could be that this is the problem. Too much peak white causing scan distortion along with the EHT falling at that current. I wonder if in the KV1320 a better 3AT2 EHT rectifier may improve things? anyone have one ?? Not sure what's causing the cogging effect on the 1300.
The pictures on lloyds set look like far better geometry. Strange one this.
Footnote: The KV1320 has just developed another fault whilst on soak test.. no sync! Currently investigating this. Oscilloscope time!