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Old 7th Feb 2021, 4:01 pm   #1
IKC2E51R8
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Default Philips GR2.2 Contrast Dims/Sound Cracks

Hi all,

Two days ago I was using my Philips Gr2.2 set to watch some music videos, Normally the picture on this set is fantastic but I noticed an issue that seems to be developing, If the scene changes from a dark scene to an all white scene the contrast dims temporarily and then returns to normal a second later, when this happens the sound also cracks.

One of the videos had camera flashes every few seconds that filled the screen white and after this the contrast got slightly dimmer then returned to normal.

I then noticed that if i turn on teletext and turn it off the same thing happens.

Ive seen on another forum a similar issue present on an L6.1 set.

Where should i start looking to resolve this? Can anyone advise?

Any help appreciated, its not a major issue as normally the picture is excellent but i want to avoid it becoming a bigger issue down the road.
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Old 8th Feb 2021, 10:53 am   #2
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Start with the simple things - check the earthing of the CRT's aquadag.
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Old 8th Feb 2021, 7:21 pm   #3
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Quote:
Originally Posted by Welsh Anorak View Post
Start with the simple things - check the earthing of the CRT's aquadag.
Good Idea, I was thinking it was somthing to do with the beam current limiter but best to start with the simple stuff, the aquadag earth never even crossed my mind. I'll take a look.
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Old 8th Feb 2021, 9:45 pm   #4
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Only had a quick look and i do think its something in the beam current limiter, just by the way its behaving, I let it run and then turned the text on, when text is on the page number gets darker after a minute, then when text is turned off the whole screen goes dull as if the contrast is turned all the way down affects the whole screen including the OSD, then a second later it returns to normal brightness (Does the same in picture mode if rapidly going from a bright to dark image and vice versa so I think (maybe) a bad cap is drifting in value a bit in the BCL. I'll have to have a proper look when ive more time and energy. Pin 15 of IC7309 is the control pin for the BCL so i might temporarily disconnect it and see if it behaves the same way or not to confirm.
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Old 9th Feb 2021, 9:35 am   #5
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Measure the HT line to the line o/p stage, could be very revealing.
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Old 10th Feb 2021, 8:59 pm   #6
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

HT is at 100.5v
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Old 10th Feb 2021, 9:46 pm   #7
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Is it steady from switch on until set is fully warmed up? No fluctuation when fault occurs?
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Old 10th Feb 2021, 10:07 pm   #8
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

bang steady at 100.5
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Old 15th Feb 2021, 5:03 pm   #9
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

does anyone have any other suggestions. I temporarily disconnected Pin 15 of the video IC to see if its in the beam limiter and its not, same result. I also changed the Peak drive storage cap and same result. Could it be the video processor itself is failing, its a TDA4680, you guys would know more than me what their reliabilty was like.

or should i be looking somewhere completly different?
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Old 27th Feb 2021, 9:24 am   #10
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Bit late to the party...

I had a GR2.4 that did similar. The picture would dim in steps, and then clear. This set was ex- rental but only 18months old at the time.
The fault was the CRT... I simply lived with it. The set with its gull wing tube gave a great picture. The rest of the family barely noticed it, just me.

If you've got access to a scope, monitor the RGB cathode waveforms, this should show if its the drive that's varying. You can use just a meter, but judgement is more difficult.

In some cases a very gentle tap the the CRT neck can bring the fault on. SJM.
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Old 27th Feb 2021, 10:00 am   #11
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

It could be as simple as a dry joint on the LOPT. J.
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Old 2nd Mar 2021, 3:50 pm   #12
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Even if it's the tube, the drive will probably vary since it uses a closed loop system for cathode bias.
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Old 11th Apr 2021, 4:34 pm   #13
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Quick Update, I still havnt solved this but after My IKC2 Ordeal I think it might be an earthing problem, the symptoms are similar, though not the exact same, the picture on the philips wobbles too but only when the volume is pushed way up, the philips is able to go much louder than the Ferguson.

I'll have to go snooping at the board and see if theres any hairline cracks or bad grounds
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Old 7th May 2021, 11:01 am   #14
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Hi!

Did you check the 14V supply? As both a part of the video section and the sound module works on this voltage, derived from the LOPT.

Measure the 14V at the CRT panel and at the sound module, are those both steady when the fault occurs? Are the capacitors around the LOPT for the 14V supply good?

Also, a fault on the CRT panel maybe cause a dip in the 14V with can causes the audio crack . .

It also can be a fault in the cut-off circuit (also using the 14V) . .
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Old 8th May 2021, 1:42 pm   #15
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Default Re: Philips GR2.2 Contrast Dims/Sound Cracks

Hi

I havnt checked the 14v supply yet, just been looking through the manual and the 14v feeds a lot so theres definatly a something in there that could be bad, when I have some spare time I'll get the meter out and test the 14v line and see if i can narrow down the fault. thanks for the tip
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