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Old 26th Jul 2010, 11:09 am   #401
oldticktock
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Default Re: GEC BT1156 First Light & Vidor CN4216

Powered back on and its reduced again,a bit of tapping helped a little but not as much as last time.

I read John W's article on his bopper, In that he suggest that a "Always run an old tube for at least 3 hours before applying the booster. NEVER boost a tube 'just to see if it gives a better picture" which is what I shall now do. If no better I think it has been established that the low emission is the cause.

If no improvement, is to be had, I will build his bopper, I have his schematic and operating guide I don't have any BY100 or BY127 or 15W bulb, so will have to source them, I wonder if IN4007's would do.

I think this is going to be an easier task than trying to sort out the CRT tester I have.

Chris

Below is John's circuit, for those interested
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Old 26th Jul 2010, 12:06 pm   #402
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Chris, this circuit is a *kill or cure*. Why not fit a crt heater transformer?
It would be a shame to strip the cathode on your crt.
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Old 26th Jul 2010, 12:27 pm   #403
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Malc,

I've probably misunderstood something here. I thought I have two issues:-

1) The low heater volts which is 1volt down
2) The cathode emmision issue (hence the bopper idea)

If I only address the heater issue with a TX is that not going to leave the cathode problem still? The reason I ask is that CRT was giving a good picture on friday despite being 1volt down, however now with the cathode issue the picture is dark.

With the brightness control sending me into negative, this is something else that has developed since friday that i previously did not have.

Any advice you have is very welcome on how I should proceed as i'm a little confused (makes a change)

I'm currently running the CRT in for 3 hours as per JW's guide, im about 1hour 20mins in.

Htr=11.7V
A1=413
Boost=524V
EHT=10kV

Another thing i've noticed and whether it has any bearing is the vision int limiter does not seem to have an great effect, perhaps another red herring


Chris

Last edited by oldticktock; 26th Jul 2010 at 12:48 pm.
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Old 26th Jul 2010, 1:10 pm   #404
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Default Re: GEC BT1156 First Light & Vidor CN4216

Although the testcard looks ok-ish that's the brightest I get without going into negative. There are issues which were not present on friday. they can been seen in pic 1 and I have tried to photo in 2 and 3

I've tried tuning I've tried adjusting the contrast and brightness, there is a hum in the background too.
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Old 26th Jul 2010, 1:25 pm   #405
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Chris,
The disturbance on the picture is Ringing, that can be caused by the set being simply slightly off tune (try the fine tuner) or mis-alignment, if this appeared suddenly its probably a decoupler going o/c somewhere in the IF or tuner. I would first try the Aurora on band 3 (channels 6-13) and try the set on a corresponding channel, if it clears there is probably instability in the tuner, but if the same it will be a fault in the IF stages or video amp, one thing to remember EF80's are not quite the same as 30F5's and sometimes EF80's can effect the alignment.
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Old 26th Jul 2010, 3:05 pm   #406
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Default Re: GEC BT1156 First Light & Vidor CN4216

Switched Aurora to band 3 and the picture cleared up all the ringing has gone, just as you said Trevor.

I then dismantled one side of the chassis and removed the tuner unit, opened it up gasped! and resealed it up. There was no way I could get at the little pF's sitting in there with pulling the internal turret apart and quite frankly at my stage of development that's one task too far and could only end in a non functioning unit.

I reassembled and checked it still worked and it did. The low emmission still persists a gentle neck tap brought the brightness up a bit.

Still not sure what to do about this and i'm still wondering about the questions in post #403

This set is just coughing up one fur-ball after another with regards to faults, a good learning set though as was the PYE.
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Old 26th Jul 2010, 5:10 pm   #407
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Default Re: GEC BT1156 First Light & Vidor CN4216

Before you give up on the tuner, try a new PCC84/30L1 & PCF80/30C1, you never know!
Make sure the screening cans are fitted.

I am sure your next set will be just a success story!!
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Old 26th Jul 2010, 7:19 pm   #408
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Default Re: GEC BT1156 First Light & Vidor CN4216

Regarding the apparent low emission:

Have you tried running the set with the CRT powered by a separate 12.6V power supply? (with appropriately rated resistor, 47R, 5W should do nicely to maintain the heater chain).

If the tube emission is marginal and you're missing a volt or so on the heater, that could make it look quite a bit worse.

I'd definitely want to see what sort of picture you get with the proper 12.6V/0.3A on the heater before considering boosting it.
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Old 26th Jul 2010, 8:19 pm   #409
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Zel,

Yup did exactly that this evening and it was better than i've been getting today but not even a touch on what it was like as of last friday. Neck tapping whilst running in that configuration aslo made it get brighter too. Power off and start all over again same scenario

I then just ran the CRT standalone on 12.6V and it draws 0.3A It sort of tends to lean towards the low emission i fear. A dedicated 12V Tx will lift it but does not provide the total solution and it was a lot better friday when just running with 11.7V !!!

This set will probably be allowed to sleep and I shall move on enough time spent already
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Old 26th Jul 2010, 8:30 pm   #410
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Default Re: GEC BT1156 First Light & Vidor CN4216

Chris!
Give the tube a boost, you are a perfectionist, you won't be happy till you kill or cure it!
Why can you not accept the set is nearly 60 years old, and the sets projected life was only 10 years?
Sit back and watch the set as it is, don't watch the test card (I hated those customers) enjoy what you have and what you have done!
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Old 26th Jul 2010, 8:42 pm   #411
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Default Re: GEC BT1156 First Light & Vidor CN4216

I would Trevor however the photo of the testcard makes it look better than it really is, when fed a source it is unwatchable and I really mean that, you have to see it to believe it.

I maybe a stickler for the detail but not as bad as people may think, Teleman will see this on friday and perhaps can vouch for the very poor state of the produced picture. This TV has developed quite a few faults since the near excellent pictures of last friday.

Enough said ,thank you all very much for the input especially Steve P,Techman,Dangerman Malc,Chris, Trevor and David B, its been a great learning session with this set, I have had some fun with the R90 mod and the removal of the LOPT with subsequent winding. I would take a photo to show but I think there is little point, everyone is sick and tired of this thread so a bow out now is probably a wise choice some you win and some you don't.

Last edited by oldticktock; 26th Jul 2010 at 8:54 pm. Reason: better grammer
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Old 26th Jul 2010, 8:59 pm   #412
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Chris.
Ok, I understand where you are coming from, never get despondent though. Think of it this way, you are doing this a hobby, there is NO customer shouting at you at 10pm demanding the set is fixed and I can assure you it was the norm. My early days were often 18 calls a day starting at 8.00am and often not getting home till after 10.00pm. So if I give you a push sometimes its not that I don't like you its to keep you on top of the repair. Fortunately the unions were very much on our side and working conditions improved, and of course customers often then had two or more sets in the house.
You have succeeded where many would have failed, for this you should feel proud, but one thing to remember and please don't forget, if the engineers had their way in the 70's none of these sets would have survived, so please remember an adage from the bible" you cant put new wine into old bottles"!
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Old 26th Jul 2010, 9:38 pm   #413
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hmm, time for one last random thought.

If we have got a bit of "crud" for want of a better term, stuck in the gun that's causing some short - would there be any mileage in giving it a tap with the heater running, either upside-down, or with it tilted quite a ways forward (though not so far that anything dislodged might land on the screen itself). Just see if we could coerce this little flake of emitter or whatever it is into actually dropping clear of the gun?

Still seems odd that this problem appeared so quickly...Would have expected a low emission tube to start as such, not suddenly become so overnight. That bit just bothers me.
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Old 26th Jul 2010, 9:49 pm   #414
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Default Re: GEC BT1156 First Light & Vidor CN4216

Hi Zel
It takes years to know "how" to tap a tube properly All joking aside it's a fine line from curing or wasting a tube. Sometime you could turn the tube around and cure the fault sometimes as you say lay it on it's face but often doing this makes the problem worse as the "crud" can build up at the end of the cathode and get lodged, it's really just your luck.
The advice I give is, live with it, find another tube, give it a blast or send it to RACS.

As Chris has said, perhaps it's time to sleep on this set and let some other threads get some attention.
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