TV22 Bent Verticals

[FRANK.C]

Hi All

This set I started work on some time ago. Before I started I read all the treads that I could find about the TV22 or TV24. Reading them has saved me a lot of grief. I would never have found that waxie hidden behind the tag bord underneath the main deck.
When I got it I first checked the transformers for continuity the LOPT was OK but that was where the good news ended. The frame blocking, fame OP and audio OP primaries were all open. The audio OP showed signs of shorted windings the others had just green spots.
Eventually I rewound them all. In the meantime I recapped it. I fitted a new EY51 one of the wires had broken off and the PZ30 with on I got from Dr-Watts.

Today I got everything put back together. I slowly powered it up on a varac and I was rewarded with a horizontal line, which I was delighted with at least I knew now that the LOPT was OK. The LOPT didn't look very good. The pitch was riddled with cracks and there was one long drip of pitch (which I removed) going all the way from the tyre to the chassis.
After a while the penny dropped regarding the frame collapse. After rewinding the frame blocking transformer I wasn't sure I got the phasing correct. I went to the frame blocking transformer and as I was figuring out which wire was which I discovered that I had connected one of the lead outs to the wrong tag on the bord putting this right got the frame working.

I connected up aurora not really expecting to get anything as two of the cores in the tuning section were broken. The Aerial tune was OK, the RF tune was completely gone nothing left only the brass piece and the Oscillator control was only quater the length it should be. But after a bit of twiddling I was able to tune in a good strong signal on channel 2. Even being able to peak it with only the brass bit.

After adjusting the controls I was able to get a pretty good picture. The only problem I have is bent verticals. There are only on the top part of the picture. They don't move like mains hum and no control has any effect on them. The line and frame hold is rock steady with a lot of range on the controls before lock is lost.

When I first got the set going the horizontal form was way off very bad cramping on the left hand side when viewed from front. As I adjusted the horizontal form it introduced the bent verticals or at least made them worse.

I have included some pictures the first one with the bent verticals and the second with poor horizontal form it can be seen even in the second picture they are a little bent

I would appreciate any suggestions in getting rid of this trouble.

Thanks in advance.
Frank

[Steve_P]

Change caps in the power supply and frame stages. The frame is on the same frequency as the mains supply, so it probably is hum. Then try the frame valves for internal leaks.

Cheers,

Steve P

[FRANK.C]

Wow Steve that was quick.

I have changed all waxes and electrolytics throughout the set.
The ECL80 field osc and amp I have substituted with a NOS I also tried it in the line osc position. But it made no difference.

Thanks
Frank

[Steve_P]

Try dropping the output of the Aurora. Or using aerials to couple it. Sometimes, the output from a Aurora is too high. Especially after a recap!

Cheers,

Steve P

[Panrock]

I've seen this bent-vertical effect before in some TV22s.

Originally Posted by Steve_P

The frame is on the same frequency as the mains supply, so it probably is hum.

Didn't think that was the case; I assumed the Aurora was crystal locked. Hum would likely cause the error to slowly fluctuate.

If you haven't already done so, try setting the Aurora to 'original signal' spec, so it no longer provides equalising pulses.

Steve

[Steve_P]

I meant in the set itself. Frame and Mains are both 50Hz. Sorry for any confusion.

Cheers,

Steve P.

[FRANK.C]

OK Steve and Steve

The contrast is turned down quite low to get a good picture so the Aurora
could be overloading it also I believe my Aurora is set with the equalising pulses on.

I will try both suggestions later on or tomorrow and will report back.

Thanks
Frank

[chipp1968]

I had this problem with my set . switching off the pulses improved but didnt remove the problem ,which I ignore as its hardly noticable .On my newer aurora it behaves like the older one with it switched off , very odd . but there is still some bend at the top

[FRANK.C]

I tried reducing the output from the aurora first by using short aerials there was no noticeable difference.
I then switched off the equalising pulses on the aurora this made a significant improvement but as chipp describes its still not gone completely but is acceptable.
I tried reducing the output from the aurora again after turning off the equalising pulses but again no improvement.

Thanks for the help

Frank

[Mike Phelan]

A couple of thoughts that might (not) be useful!

Often the cause of this symptom is that something from the frame timebase or frame sync is getting into the line sync; especially on a set without flywheel sync.

This may be signal-related and nothing to do with the sync separator stage.

[Duke_Nukem]

Unless it was co-incidence, the kink is always at the top of the pic ? If so, then can almost certainly rule out 50Hz mains as the cause.

I'd re-check the sync seperator, recheck resistors in that area, then triple check associated caps (value/position - easy to get em mixed up - been there, got the teeshirt ) and of course re-check voltages. Is the kink pretty much constant or is there any variation with time e.g. as set warms up ?

TTFN,
Jon

[Mike Phelan]

... if so, get the can of freezer and hairdryer out.

[beery]

Hi Frank,
from my website...

Poor line lock: This fault is probably only experienced when using certain standards converters. Standards converters can produce minute spikes in the video waveform ,but the only sets affected by this are very early TV22's, it is actually due to the sync separator having to higher a frequency response making it very sensitive to interference spikes. Within the first year of production a modification had been introduced in the form of a 10pf mica capacitor (C32, note this is C22A in trader sheet 1003) between the grid of the sync separator and chassis, if you have to fit this modification I recommend that you use a 50pF capacitor instead.

Cheers
Andy

[FRANK.C]

Hi Mike, Jon and Andy
Thanks for the replies.

The bent verticals are the same shape and size all the time they are more like waves running from the top of test card C down two squares and stopping at the bottom of the second one down. There is approximately one full wave per square and are strongest at the top. They don't change with time either.

Line hold is really rock solid I have to turn it 90% fully clockwise before lock is lost and it then goes straight into a black bar appearing up the center of the frame. Likewise I have to turn the line hold 95% fully anti clockwise before line lock is lost then it almost goes straight into multiple views of the frames.

I will try and get some work done with the suggestions tonight and report back later on.

Frank

[FRANK.C]

The cap that Andy suggested wasn't in my set, the nearest I had to hand was a 15pF . I fitted it but no improvement.

I checked the caps and resistors around the sync separator / line osc area. The anode resistor in the line osc had risen from 820K to almost 1M. I changed it but it made no improvement.

I decided to have a look at video wave form on the scope. I connected the scope to the point where the video enters the main deck. This made the bent verticals a lot worse and they now were the whole way down the screen . The distortion being at the same frequency and not moving as before but more of a square wave. I connected the aurora to a dvd player and the distortion went back to as before the scope was connected.

Time ran out and I had leave it for tonight

Frank

[Steve_P]

Try turning R14 down a bit?

Also, the scope capacitance has obviously made it worse. Check the resistors on the RF deck towards the end, and the start of the main deck. Is the wire screening OK. Try giving L12 half a turn in either direction to see if this clears it.

Cheers,

Steve P

[FRANK.C]

Steve
Thanks for the suggestions

I will try them.
I wont be able to do anything tonight it may have to wait until the weekend.
As soon as I do I will report back.

Frank

[FRANK.C]

Well I got too spend some time on the set this weekend but not as much as I would like too, the weather was good and there was too much to catch up on outside.

The interference limiter I leave set at minimum always.

There is no screening at all on the video wire and it looks original.

I checked the valve voltages on the RF deck all were OK except for the cathode of the video amplifier which was low .7V. The cathode resistor was changed at some point and replaced with a 100R. I replaced it with its original value 270R.

I checked all the hi value resistors on the RF deck and most of the others.
I noticed that the decoupling capacitors in the cathode circuit of V1 And V3 was not in my set and I fitted them.
I checked the resistors on the main deck around the sync separator and line time base. The grid resistor of the PL38 had risen from 470k to 670k . I replaced it.

All the above made no difference

I tweaked the coils on the RF deck which made a little difference.

I noticed that if I adjust the line hold very carefully, just before hold is lost the picture jumps about 1 cm to the right and I have perfect verticals.

Maybe its happening because the aerial, RF and Osc coils haven't got there proper cores?


Frank