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Frame transformer for BRC 960

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Focus Diode
(@focus)
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Hi Jon,

It's another bit of dirt that decided to enter the set between the CRT face and the implosion guard sheet. Very annoying as it means dismantling the set and moving the CRT to clean again. Obviously my attempt of a draught excluder seal wasn't very good.

It's a very crude arrangement having the CRT face resting on the PVC sheet not quite the same size then secured to the cabinet by a plastic cradle.

Cheers and looking forward to hearing more about your Ferguson.

Brian

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Topic starter Posted : 23/05/2018 6:02 am
Focus Diode
(@focus)
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Well the set is working well but still plagued by the intermittent ragged verticals problem sometimes accompanied by picture breathing.

It's similar to the effect given when the EHT tray is breaking down, only that the setting of the brilliance control makes no difference.

The set has always suffered from this intermittent problem. 

New PL504, PY801, 30FL14, EF80 and PFL200 valves have been tried.

The EHT tray and line output transformer aren't the original of course, but have fitted new diodes in the EHT tray.

The fault was present before they had to be replaced anyway.

Frame and line hold is rock steady.

Any ideas?

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Topic starter Posted : 16/07/2018 3:50 pm
Doz
 Doz
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Is the dag connection sound?

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Posted : 16/07/2018 4:39 pm
Focus Diode
(@focus)
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Hi Doz,

Yes it is. I've also thoroughly cleaned the CRT and the spring.

The problem is only apparent after the signals fade in so could be related to the secondary stage in the heater chain. It's also intermittent, sometimes present when the signals fade in, other times after a few minutes.

I don't recall seeing this on 625-lines however. I must connect a signal source and give the set a good run on 625.

In due course I'll be dismantling the set again to clean the CRT face. This time I'll be adding masking tape to help prevent the dirt accumulation from happening again.

 

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Topic starter Posted : 17/07/2018 10:39 am
Focus Diode
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Working beautifully now. 

1). Raster appears after 40 seconds.

2). Pictures appear after another 45 seconds.

3). Sound appears after another 30 seconds slowly reaching to full volume.

Off air BBC 1 pictures.

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Topic starter Posted : 08/09/2018 4:20 pm
Focus Diode
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The set continues to work well apart from two problems.

First the intermittent ragged verticals. Despite the otherwise solid line lock I'll change the flywheel sync discriminator diodes in due course. The fault isn't heat related.

I was incorrect in assuming this affected 405-lines only.

Secondly the EHT regulation isn't very good. I'm aware that modifying the set to take a 1400 Lopt the EHT is slightly lower than it was with the original one. Occasionally there's picture breathing but this usually settles after a few minutes.

Thirdly, the one I dread. Looks like I'll have to dismantle the set again and remove the CRT for cleaning. My attempt at using draft excluder as a dust seal has failed. Perhaps next time I'll secure the surround with masking tape or similar.

Screenshot shows the ragged verticals. It can suddenly appear at anytime then go just as quickly to leave a beautiful clean image.

Brian

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Topic starter Posted : 08/10/2018 3:43 am
Lloyd
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Hi Brian, 

those ragged verticals look familiar, I had the same effect on a Philips set not long ago, it turned out not to be the set at fault though! It was something funny about my setup with the Aurora, AV switcher and VCR/DVD thing. For some reason when there was no signal the aurora would be putting out the test card as expected, but then something between the AV switcher and the DVD player would suddenly cause random blasts of these ragged verticals. I only found out when another set on at the same time started doing it too! I still haven’t got to the bottom of it, but at least I know it’s not the set.

Regards,

Lloyd

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Posted : 08/10/2018 9:28 am
Nuvistor
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It looks very similar to poor earthing of the dag coating, if that is ok then there is the horrible thought of poor dag connections to the final anode inside the crt.

Not something to usually worry about in BW crt’s but shorting out on a colour crt was not recommended by Mazda. The said use a resistance to remove the charge, it could damage the dag coating inside the crt.

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Posted : 08/10/2018 9:43 am
Nuvistor
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Oh the joys of the bonded screen or the Panorama crt’s, no dust getting through the seals .

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Posted : 08/10/2018 9:50 am
Focus Diode
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Posted by: Nuvistor

It looks very similar to poor earthing of the dag coating, if that is ok then there is the horrible thought of poor dag connections to the final anode inside the crt.

Not something to usually worry about in BW crt’s but shorting out on a colour crt was not recommended by Mazda. The said use a resistance to remove the charge, it could damage the dag coating inside the crt.

It crossed my mind that the CRT could be responsible. The set has always suffered from this intermittent fault this rules out the valves, Lopt and doubler. The effect is similar to what I've seen on sets with a failing EHT tray, the symptoms worsening at higher brightness settings, almost disappearing at lower settings.

Only the setting of the control has no effect.

Ideally I would love to obtain a good CME1602 for the set which wouldn't require the crude implosion sheet. There's actually corners in the cabinet that would allow such a tube to be fitted.

When I get round to dismantling the set to clean the CRT I'm tempted to check the chassis in the 16" Ferguson 3645 set assuming replacement flywheel sync discriminator diodes doesn't cure the problem. I'm not optimistic it will do to tell you the truth.

But it would prove if the CME 1601 is at fault or not.

Brian

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Topic starter Posted : 08/10/2018 12:23 pm
Focus Diode
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Just remembered the "Television" piece about a none working 1500 that came in for repair. Don't remember the author, might have been Robin D.Smith?

Anyway the CRT was found to have an o/c heater. The customer agreed to a replacement so the usually straightforward job of CRT replacement was done.

He found the picture ballooned excessively on test with an accompanying dark patch. Classic low EHT.

Tried a new EHT tray and everything else that could possibly cause the fault including fitting a new Lopt to no avail.

It was only when he tried connecting the CRT etc to a known working set the fault showed up on that too. The new CRT was at fault.

Of course he wasn't able to charge extra for all the extra work he endured.

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Topic starter Posted : 08/10/2018 4:37 pm
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