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Old 1st Feb 2007, 10:32 am   #1
cornboats
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Default Philips K35-No picture or sound

My Philips tv is faulty- Anyone got any ideas?

1) Its a full raster with snow - no sound ,only hum.
2) Its electronic tuning with tuning bar . I have noticed that when working properly the bar travels full width of screen but now cuts short 2/3 of way and then starts again.
3) D401 has 33.8v

Same symptom happened a couple of weeks ago and I changed memory battery which cured fault . This time battery is ok. I did wonder if there may be a fault near battery but haven't got this section on my Philips k35 drawing.
Can anyone let me have this section and mains in section where the ac transformer is. 600ma fuse is on this secondary board aswell.

Prior to complete failure set was coming on channel in black and white, it took channel hopping to restore colour. I've no idea why , perhaps someone could explain.

Any help for a 2nd year electronics student would be welcome.

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Old 1st Feb 2007, 9:40 pm   #2
MALC SCOTT
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Default Re: Philipps k35-No picture/sound

Check voltages around the tuner unit. Some Philips chassis had plug in tuners which gave int problems with connections. Refer to your manual for supply rails to the tuner.
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Old 1st Feb 2007, 10:12 pm   #3
Heatercathodeshort
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Default Re: Philipps k35-No picture/sound

Hello ?,
Just a thought: Switch set off. Unsolder the back up battery and leave for a few moments. Resolder and try again. I had one of these stuck in standby after changing the battery, and it took me around an hour to trace the fault.

The micro might have 'glitched'. Failing this, I think the tuner should have two separate 12v supplies plus the varicap line [33v].
Does this voltage vary when you scan the tuning?

As for the colour drop out; does your version use a TDA3650 colour decoder chip? If so, it is probably plugged into a white holder. Remove the holder, shape the chip lead outs to fit the printed panel and solder it direct to the board.
That should clear up any colour oddballs. [This also applies to the CTX series] Do not twiddle anything...

Regards John.
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Old 2nd Feb 2007, 12:46 am   #4
ben
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Default Re: Philipps k35-No picture/sound

Check to see if the battery you replaced oozed on to the pcb.
I've seen numerous sets where nearby traces had been affected by this. Could give rise to odd faults like yours.

Last edited by Mike Phelan; 16th Nov 2007 at 11:57 am. Reason: Legibility
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Old 2nd Feb 2007, 6:41 pm   #5
cornboats
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Default Re: Philipps k35-No picture/sound

Malc Scott, Heatercathodeshort & ben: many thanks for your ideas. I'll work through all your suggestions & then come back.

Meanwhile, has anybody got a copy of schematic to first pcb where mains comes in?
It's not on my main K35 schematic. It's got a 240vac transformer on it.

cheers

Last edited by Mike Phelan; 16th Nov 2007 at 11:59 am. Reason: Punctuation
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Old 11th Feb 2007, 11:00 am   #6
cornboats
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Default Re: Philipps k35-No picture/sound

I've checked tuner voltages as suggested. & details are
tuner U8 a).22v,b)11.66v,c)10.2v,d)11.65v,e) .25v,f).2v, g)10.2v -fixed.H) 0v.

I traced the voltage supply back from h through c410, R410 to IC101, The print track continues underneath IC inot a network of resistors, diodes.

I'm stuck now because my main schematic doesn't cover this board.

Can anyone help?

I removed back-up battery overnight and then re-instated -no change.
The old one hadn't left any deposit.
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Old 5th Mar 2007, 10:05 am   #7
cornboats
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Default Re: Philipps k35-No picture/sound

I found the fault in the end. Tuner was getting variable voltages in, but nothing out.
I stripped the unit down, and found the only transistor short circuit.
Changed for a near match, and set now has full picture and sound.
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