Oh no - another V4!

[dominicbeesley]

Thanks Steve,

C103 was changed fairly early on in desperation. It looks like the power supply caps have a lot of ESR causing the ripple but my main concern is the low width I'm sure there should be more! Everything else measures ok....

Dom

[dominicbeesley]

Sorry meant to add that all supply voltages measure within a few volts.

I've decided to rewind the width coil anyway as it is full of goo. 950 turns to put back on! Will take me a few days probably!

Dom

[dominicbeesley]

Hello all,

Been away on my travels but got straight back on the case of the skinny VT4 picture when I got back.

This afternoon I rewound the width coil which I'd dismantled before I went away... there was a marginal (hardly noticeable) increase in width. But probably more due to moving the former so that more of the iron slug could go into it.

[That is to cut a very long story short, tales of woe including dropping a brand new reel of wire on the floor which broke and unwound itself; loosing count in the middle of winding the coild five times; building a coil winder / turns counter; etc etc]

To calm down I decided I'd make a new test-card DVD, my old one being scratched - I'd got sick of Test Card C and it's 1kHz tone.

Imagine my surprise when I put the DVD in to find I got a TOO WIDE picture! Looks like I've been on a wild goose chase - the built in Test Card C in the Aurora is too skinny! Is this a fault with the Aurora - I'm pretty sure this is the original built in Test Card C picture!

The scope traces below show TCC from the Aurora at the top and from the DVD on the bottom. The bottom trace looks more correct to me! Middle picture is Aurora Test card - screen edges at edges of picture. Last two pictures are from DVD again screen edges at edge of picture...

At last I can stop ****ing around with the width and attack everything else!

So is the DVD right or the Aurora....please say the DVD!

Dom

[KeithsTV]

A colleague of mine had an Aurora which had too narrow a test card. We proved it by checking the video output.We then put a new version on the Aurora from a file sent over by Darryl. It must have been about 2 years ago when we updated the converter so any bought before then may have a narrow test card. All recent Auroras have a correct width card.

Keith

[brianc]

Hi Dom
Even though the modulation from the Aurora did not fill the width of the CRT, the raster could have been seen if the brightness had been increased. I always judge the width of scan available from a set using an unmodulated raster running at approximately the correct line speed. In this way, there are no misleading results! I have been caught out using a freeview box showing letterbox, thinking that I had lost height!
Cheers
Brian

[Geoff 555]

Hi there, is there any way of knowing if you have a model with a narrow test card I bought mine just over 2 years ago and always was somewhat puzzled by the difference between the test card which meant that the width was Only just enough with the width set at max (TV22.) and a program/film. I put it down to the old DVD player which was the cheapest of cheap but totally reliable.
Rev 2.0/2.2.
Thank you very much.
Cheers.
Geoff.

[DangerMan]

The difference should be visible if you look at the video waveform on a scope.
The active picture information should start 7.5uS after the end of the line pulse, and should end 1.5uS before the next pulse begins. During these periods the picture is at black level.
The line pulse itself is about 9uS wide (below black level).
HTH
Pete

[dominicbeesley]

Thanks lads, mines a 2.0/2.1 - seems that Darryl had flashed it with a 5:4 testcard pillarboxed onto 4:3 output....most confusing. I had noticed the raster being wider at one point but forot for some reason - rest of the time I've had the brightness adjusted correctly so not spotted it!

Oh well only wasted about 40 hours messing around cooking lopts etc!

Now I can get on with some real mucking about with the set getting it perfect - expect me back with daft questions later!

Dom

[KeithsTV]

Checking I have found references to the low width testcard dating from late August 2007 with an email from Darryl to my work colleague staing he's reflashed all converters in stock. So any Aurora purchased after September 2007 ought to have the correct width test card. As Dangerman says check the video waveform on a scope.

Keith

EDIT. I'll try to remember to take my converter to work on Monday and make some plots of the line waveform and post them. My scope at work is definiately better for this than my cheapo scope at home.

[dominicbeesley]

I can't remember when I got the Aurora but the picture above shows the relecant scope traces...

Ho hum, is not all wasted I'm sure the LOPT will be a lot more reliable for its long bake!

Does anyone think it worthwhile spraying it over with a good dose of anti-corona lacquer to seal it?

Dom

[murphyv310]

Hi Dom
I suppose I am lucky, what I do is I program my RT Russell test card generator with an appropriate test card on 625 lines and then connect to my Aurora and then do a flash!
The results are first class and the "test card" is always spot on!

[KeithsTV]

I remembered to take my converter into work and during my lunch hour I measured the active video times using my works DSO.

I measured line 85 which looks to have white at the start and end of the line. The attached plots show a full line of video approx 80.4uS and the line blanking period approximately 18.4uS.

The pdf shows the spec for the horizontal sync for 405lines, and also 625, 525 and 819 line.

Keith

[Heatercathodeshort]

I would leave it well alone Dom. These transformers were designed to 'breath' with heating and cooling. If sparayed with something that does not have any 'give' in it you may find you end up with a fractured internal wire..... It will last another 50 years...probably. J.

[dominicbeesley]

Thanks Keith, Trevor

That's pretty what mine looks like when playing back from DVD. I've got to get better to grips with the DVD authoring thing before I make a proper test card to burn into the Aurora - all the ones I've done so far have problems with the higher frequency gratings - is this the Aurora filtering out chroma?

John, righto I'll leave it - I just wasn't sure as quite a lot of "juice" came out when I cooked it!

I've been plugging away at the various other faults - main one still is the line and frame timebases are quite twitchy. But once set a bright sharp watchable picture results. Also there's bit of overshoot/ringin on video caused by the video amplifier valve - not sure what to do with it but will plug away at it - I cured the smearing by deduction - the leg to the brightness capacitor was broken...

There's still a tiny bit of hum - but I'm not sure whether its due to smoothers or other things (h-k leaks, etc - I've sorted most of the hum problem out by swapping valves and in one case cleaning the valve socket). One question what *should* the ripple voltages be at the reservoir and main smoother?

Today I've started on the cosmetics - first up the cabinet has been knocked about a lot so I'm going to give it a full strip down and French polish.

The screen "surround" I've noticed is nothing more than a few scruffy bits of timber painted black and the corners stuffed with some sort of felt. This is barely noticeable with the perspex in place but looks a bit half-arsed to me - is this a dodgy repair?

Also, look at the state of the CRT! Its got a number of bubbles right in the middle of the picture and the glass lucks more like something out of a bathroom window! All perfectly unnoticable when watching. So now we know why the purple perspex, you can use CRTs that would otherwise be binned!

What I'm not sure about is what to do with the tatty looking chassis. I could always mask off, Kurust and spray the top but there's no way I'm stripping under the chassis so the rust there will have to stay. I'm half tempted to just leave it as is: most people who see a working vintage telly at a rally would be mislead into thinking a chassis has to be shiny and neat to work - my set would disabuse them of that!

Cheers

Dom

[oldticktock]

Originally Posted by dominicbeesley

The screen "surround" I've noticed is nothing more than a few scruffy bits of timber painted black and the corners stuffed with some sort of felt. This is barely noticeable with the perspex in place but looks a bit half-arsed to me - is this a dodgy repair?

Nope this is by design including the felt, which stops light from the back of the tube breaking forwards.


"The appearance of these models was quite different
from anything seen before. The screen was not masked by
the usual overlapping contoured moulding and thus provided
the maximum picture size of which the tube was
capable. The tube face was surrounded by a wooden
frame that was painted matt black, and black cotton
material filled the corners."

You might find this useful for removing the implosion screen once its all assembled and you find yourself wanting to get that elusive bit of fluff removed and cannot face removing everything but the kitchen sink.

"I was seated at the bench gazing through
the hatch of an up-ended V4, stumped by an elusive fault.
Idly, I noticed a slot running from side to side of the
cabinet bottom just beneath the implosion shield. What
was it for? Grooves ran up to the bottom of the tube
mounting frame, but the loudspeaker assembly straddled
the path. This I discovered could be removed after taking
out a single screw. Underneath was a strip of sealing tape,
and when this was removed the implosion shield could be
slid downwards through the bottom of the cabinet. So
cleaning could be carried out in a matter of minutes,
without any disturbance to the tube.
Somewhat shamefacedly I consulted the service manual
to find out how I'd come to miss this important piece of
information. But there was not a single word on the
subject"

Wow yours was very rusty, mine was fine underneath no rust with light rust on top, which I used WD40 on and a stiff brush

[dominicbeesley]

Thanks Chris,

I suspected it might be proper old fashioned British perfectionism at play!

I'd been tipped the wink about sliding the screen out by John. I'm going to leave it out while I do the cabinet but not remove the tube so I hope it doesn't implode, the perspex looks like It would take a scratch quite easily!

Dom

[oldticktock]

Originally Posted by dominicbeesley

I'd been tipped the wink about sliding the screen
Dom

Wish someone had done that for me! when I was at that stage.I had it in and out quite a few times and only got access to that info by chance right at the end when I had finished the V4.

At least it's in the open, within a thread now that others can search and find.

Looking forward to seeing your ends results.

[murphyv310]

Hi
It's really surprising how many engineers didn't know about the removal of the perspex screen. I remember cleaning my V4's screen in the British Relay workshop in 1970 when I was 16 and the engineers then didn't know about it, I think Mr Pye kept it under his belt to catch the engineers out!
My V4 has a really rusty chassis other than an odd spray with WD40 it will be left that way, it's all in the history of the set and I wouldn't dream of doing all the work in putting it right.

[mark pirate]

Looks like my v09 perspex will come out the same way, it certainly needs a clean

Mark

[dominicbeesley]

Cheers lads,

Glad I don't have to feel too bad about cleaning the chassis...nowt wrong wi a bit o rust.

I have to say taking the screen out will have been worth it - applying a bit of meths to the screen has taken off a very thick layer of nicotine and also the inside of the perspex. It might be a while before I come back with updates now as I'm into cabinet finishing mode and am likely to get bored and sidetracked back onto other projects...my thumbs are knackered after a few hours of cabinet scraping!

Dom