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Old 23rd Sep 2021, 8:58 pm   #1
phildil
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Default Philips CRT TV ... can it be revived?

hi all

my trusty CRT TV has recently given up and I really should get around to sorting it out.....

It is a Philips 28/PW6008/38 28" widescreen model from 2004. One moment it was running as usual then the screen suddenly went off in the classic "disappearing dot" style, and of course it will now not power up at all.

I suspect a PSU board fault, but before I get the back off, I'm sure someone out there has some experience of these sets and can advise if worthwhile my pursuing it? I don't intend to "upgrade" to a flat screen (yuk) but instead a similar big old TV can easily be found to replace it if this is going to be a bu**er to fix.

Any thoughts?

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Old 23rd Sep 2021, 11:07 pm   #2
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Default Re: Philips CRT TV ... can it be revived?

If it has completely died - no standby LED or noise - start by checking the basics first: plug/fuse connections, mains switch & fuse in set, rectifier, etc. For all you know it might be a cracked solder joint or a momentary surge that killed the fuse. Check and post back.
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Old 24th Sep 2021, 7:54 am   #3
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Default Re: Philips CRT TV ... can it be revived?

Trying to ID what chassis is fitted, please post a pic of it please.
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Old 24th Sep 2021, 8:05 am   #4
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Default Re: Philips CRT TV ... can it be revived?

/38 suggests it's not a UK model. I worked for Philips for over 30 years until 2008 and that would be one of their later and last run of CRT models but I've never heard of it.
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Old 24th Sep 2021, 9:59 am   #5
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Default Re: Philips CRT TV ... can it be revived?

Quote:
Originally Posted by toshiba tony View Post
Trying to ID what chassis is fitted, please post a pic of it please.
L04 chassis, according to Google. This suggests a basic set, not Matchline or something like that.
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Old 24th Sep 2021, 10:05 am   #6
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Default Re: Philips CRT TV ... can it be revived?

Thought it didn't ring a bell.
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Old 24th Sep 2021, 10:47 am   #7
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Default Re: Philips CRT TV ... can it be revived?

A quick glance at the manual suggests this is quite a conventional set (for Philips!). Follow Ben's advice - how dead is dead? If there's some sign of life then a look at the line output stage to see if there's a short will be the next step.
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Old 25th Sep 2021, 11:00 pm   #8
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Default Re: Philips CRT TV ... can it be revived?

On these CRT sets it wasn't unusual for the degaussing positor to fail, and that will blow the fuse of course.

Also check for dry joints and exploded small (usually blue)
ceramic capacitors in the line O/P stage, the transistor may also have failed. Hopefully the LOPT will be OK

l've still got a few transistors and positors in stock if you need one. You have to fit the correct line O/P transistor, for instance if it's a BU2508AF, a BU2508N won't do.
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Old 26th Sep 2021, 6:49 am   #9
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Default Re: Philips CRT TV ... can it be revived?

My Dad would have said if it`s a Philips it`s most likely a dry joint.
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Old 26th Sep 2021, 10:51 am   #10
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Default Re: Philips CRT TV ... can it be revived?

On the L04 chassis I had several lopt failures and this often took the frame chip with it as well, this gave the same symptoms as the lopt. ie. shutdown.
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Old 26th Sep 2021, 2:07 pm   #11
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Default Re: Philips CRT TV ... can it be revived?

Check for dry joints on scan coil socket.
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Old 26th Sep 2021, 4:33 pm   #12
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Default Re: Philips CRT TV ... can it be revived?

Oh yes l remember that one! The socket on the CRT base mainly gave issues.
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Old 27th Sep 2021, 9:28 am   #13
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Default Re: Philips CRT TV ... can it be revived?

Amazing how you forget the obvious one! Must have repaired hundreds of those small scan coil PCBs. Also the mains switch sub-panel and switch itself.
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Old 27th Sep 2021, 12:55 pm   #14
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Default Re: Philips CRT TV ... can it be revived?

l've still got a box of various TV mains switches if anybody needs one, including the CPC "universal" switch (not for Sony)

The CPC order code was SWMS40
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Old 8th Oct 2021, 8:07 pm   #15
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Default Re: Philips CRT TV ... can it be revived?

Thank you all for your info and suggestions so far. I have now been into the set and there are no exploded blue caps and all fuses are OK. The main switch is OK and the main board is getting 240v AC. Following through the schematic, I have found what looks like a duff rectifier and a shorted diode on the PSU stage. I shall replace both parts (and I'll be pleasantly surprised if that's all that needs doing); to do this the main board needs to be removed. All cables are plugged into the board except for one, which is the red cable connecting the LOPT to the anode of the tube via a rubber cap. Is this designed to be removed?

ta
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Old 9th Oct 2021, 9:01 am   #16
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Default Re: Philips CRT TV ... can it be revived?

If you mean the EHT lead, then just squeeze the rubber bit on the tube (to close the claw) and it will pull out.
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Old 9th Oct 2021, 9:29 am   #17
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Default Re: Philips CRT TV ... can it be revived?

Would this be a good time to explain how to safely discharge a tube?
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Old 9th Oct 2021, 11:13 am   #18
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Default Re: Philips CRT TV ... can it be revived?

I think it might.
The tube can hold a charge for surprisingly long time, and I'll bet all of us TV engineers on here have found that out to their cost!
Discharging is easy. Simplest way is use a long bladed screwdriver which you earth to the tuibe's metal mounting frame using a wire with crocodile clips on each end. Slowly introduce the screwdriver's tip under the rubber sucker until it touches the metal connector. There might be a crackling as this is done. Then the connector can be safely removed.
This holds good for most relatively modern tubes with the exception of some Sony CRTs that use a co-axial fitting. However these have bleed resistors so should be safe to remove after a short while.
There are rumours of some slapdash engineers that use a pair of crossed screwdrivers to do the same, but I couldn't possibly comment on that...
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Old 9th Oct 2021, 12:00 pm   #19
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Default Re: Philips CRT TV ... can it be revived?

Yes once you know how, they're a doddle to remove (safely, of course!). I find sliding the cap slightly left or right before pulling it away helps disengage the prongs with relative ease.
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Old 9th Oct 2021, 12:42 pm   #20
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Default Re: Philips CRT TV ... can it be revived?

Discharging to the mounting frame (the tension band and tube mounts) might not be the best idea in general, as it sometimes isn't directly connected to the aquadag (the carbon conductive layer on the bell of the tube). In this relatively modern set, it's probably all connected together, but when in doubt, discharging should be done to the aquadag only (via its connection strap). In modern sets the discharge could theoretically disturb IC's, so officially you should use a HV probe instead of a screwdriver. I've always used a screwdriver, though.

Last edited by Maarten; 9th Oct 2021 at 12:51 pm.
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