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Old 10th Jul 2020, 5:55 pm   #1
Kyle__B
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Default Philips F6 problem after fixing vertical collapse

I know what you're thinking again, another one of those Kyle threads about that F6 Philips. I know I'm tired of them.

This time is a bit different, but so everyone knows what's relevant to this time around:

This TV had a couple of weak PCL805s and it took ages for the picture to fill the full height of the screen. Usually about five minutes, maybe a bit more. It'd also make a sort of electric crackling noise around the frame part of the chassis for a second when it was first turned on.

At the start of the week I switched it on and got greeted by a puff of smoke out the back and a vertical collapse. Classic bright white horizontal line.

Had a nosy inside and found the smoke came from a little 100 Ohm resistor, which connected on one end to a transformer and then a PCL805 cathode, and on the other end 250V from the power supply section.

I gave the 805 a wiggle and it felt loose. I think it probably shorted out and pulled too much 250V, causing the resistor to sacrifice itself to protect the transformer.

So I've put in a new resistor, changed the valve socket, and while I was there I've also put in new 805 valves. Turned it on, no vertical collpase anymore! Instead I got this psychadelic effect in the pictures.

You can see it in video here: https://www.youtube.com/watch?v=uFxJlsF2cXo


So that brings me to my question. There's two knobs on the back of the telly marked "Linearity" and "amp", could it be that they got turned up by a previous owner to compensate for the weak valves, and with new ones it's far too high?

Do I just need to turn them back down to bring it back to reality? Or is it something else now.
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Old 11th Jul 2020, 12:39 am   #2
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Default Re: Philips F6 problem after fixing vertical collapse

Have twiddled amp and line controls, made it only slightly better. Seems to be a more serious fault.
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Old 11th Jul 2020, 5:42 am   #3
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Default Re: Philips F6 problem after fixing vertical collapse

OK so gave the two knobs on the back a twiddle, could adjust the height of the raving madness on screen but little else.

Returning to the chassis I looked around what else is on cathode of B407p. Other than the transformer and burnt 100R resistor to 250V, it also has C651, which is a 0.1uF 400V polyester cap leading to R916, a 100K half watt resistor marked for 5 or 10% tolerance.

Those are undamaged and test fine. Between them R917 connects to wire number 23 who goes up to the emmitter of TS413 a BF185 transistor which I think is on the neck board.

R917 is a very strange beast to me, not having a value on it just beige with a single green stripe. The drawing is just a box with an arrow through and "-U" written next to it. All I know is it doesn't look damaged.

I'd be interested to hear your thoughts.
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Old 11th Jul 2020, 9:37 am   #4
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Default Re: Philips F6 problem after fixing vertical collapse

It looks like a frequency problem to me after looking at the YouTube video. A simple question: have you tried carefully adjusting the vertical hold? Quite often, different PCL85/805 valves had quite differing frequency characteristics.
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Old 11th Jul 2020, 9:48 am   #5
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Default Re: Philips F6 problem after fixing vertical collapse

The F6! New chassis on me, Interesting.
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Old 11th Jul 2020, 3:10 pm   #6
Kyle__B
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Default Re: Philips F6 problem after fixing vertical collapse

Quote:
Originally Posted by Tazman1966 View Post
It looks like a frequency problem to me after looking at the YouTube video. A simple question: have you tried carefully adjusting the vertical hold? Quite often, different PCL85/805 valves had quite differing frequency characteristics.
I haven't tried that yet, it's in a very awkward place being a vertical trim pot on the component side of the board. Would have to be a plastic screwdriver job.

Instead I put the old low emission valve back in and it's still doing it.

It's a funny thing, it's not a rolling picture, just holding for a couple of seconds before it jumps, although it's all shifted down with picture from the bottom third of the screen then ending up at the top. Like it can't tell where is the beginning and end of each field of video.

White lines across the whole thing too, very tightly bunched at the bottom third. Retrace lines?

The vertical collapse happened on a day I'd already been watching for a couple of hours, with the chassis swung down. I turned it off, folded it up, turned it back on and got a burnt resistor and a big bright white line.

Makes me think could be that wire 23 to neck board amplifier?
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Old 11th Jul 2020, 11:37 pm   #7
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Default Re: Philips F6 problem after fixing vertical collapse

OK had a look at neck board, no broken wire there.

Put new PCL802 in, turned on to try adjusting vertical hold as tazman advised

Greeted by total gibberish picture and PCL805 making a high pitch noise and glowing red on it's triode side. I suspect this is because R919 vhold control has responded to being turned gently by breaking?

Should I just skip this thing? If Maarten guy sees this, and he wants to drive up near Nijmegen, you're welcome to take this TV away from me. The chassis is cursed, the mechanical tuner is gone, but the picture tube is very good and the cabnet is in a reasonable condition. At this point I would really rather have a solid state TV.

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Old 12th Jul 2020, 12:21 am   #8
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Default Re: Philips F6 problem after fixing vertical collapse

Just checked one last time, glowing red on both triode and pentode very quicky, before even the heaters glow is visible. It's like it's suicidal.
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Old 13th Jul 2020, 12:28 pm   #9
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Default Re: Philips F6 problem after fixing vertical collapse

I appreciate the offer! It would get to stay in the 'round tuit' pile for at least some months though, but I intend to update this topic if and when appliccable.

Normally the drive would be a bit far, but I happen to be in the vicinity of Nijmegen shortly. I'll send a PM.
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Old 13th Jul 2020, 5:05 pm   #10
Kyle__B
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Default Re: Philips F6 problem after fixing vertical collapse

Maarten comes riding over the hill in shining armor! You have a reply to your PM with all the gory details.
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Old 15th Jul 2020, 3:21 am   #11
Kyle__B
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Default Re: Philips F6 problem after fixing vertical collapse

Hello again all. After leaving it alone a couple of days I've gone to clean it up a bit before Maarten comes round to collect. For the sake of keeping a record of what's going on:

I just redid all the solder joints in the frame area, now it doesn't roll anymore, and it isn't instantly overheating the frame valve either!

But the picture is doubled up, sometimes folded over upside down on itself, and has white horizontal lines.

https://www.youtube.com/watch?v=9oIMnyChWMk

https://www.youtube.com/watch?v=9Nu4FR7QSkE

I've noticed that the replacement for R918 is slowly burning up. Slowly going brown and smelling a bit burnt. The schematics don't list a watt rating, so I looked at the size of the old one and guessed it was about 1/4W. It's possible that the one that was in there was itself a too small replacement.
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Old 15th Jul 2020, 7:13 pm   #12
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Default Re: Philips F6 problem after fixing vertical collapse

TV is now safely with Maarten. Really nice guy, was good to meet him.
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Old 16th Jul 2020, 1:03 am   #13
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Default Re: Philips F6 problem after fixing vertical collapse

Likewise! Also, the set certainly seems worthwhile to restore, it looks really nice and I've understood the picture was really crisp when it worked properly. The modifications were documented neatly and the original parts came with the set in a box. I hope to update this topic in a few months time.
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