Phillips TV 27pt543s37a ch#L01.1u AC-7638

bullvwMay 28, 2005

For those of you who've found that a little bird is keeping your tv from powering up, set goes tweet tweet tweet when plugged in, It may be that transistor 7460 has gone short. From the Philips service guide, it is recommended to unsolder one leg of coil 5561 to see if the noise stops. If it does it points to 7460 being bad. There is also a article at

that lists the most common parts replaced by Philips techs on a dead L01.1 chassis. The schematic for this chasis can be found at

Now, if I can just find a source for the parts.

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    Bookmark   June 1, 2005 at 11:38PM
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try this site for parts and let me know....
yhey seem to have alot of parts...

    Bookmark   June 2, 2005 at 5:19AM
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I went to that link for that you posted and nothing seems to work. If you can email me a downloaded copy that would be

    Bookmark   June 2, 2005 at 12:53PM
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Lately, I have had to power on and off the TV 3+ times before the picture finally catches. The first time, the picture comes in fuzzy for a second and then disappears. The second time, the picture comes in a little clearer for a few seconds, then disappears. The third time, the picture comes in better, waves a bit and then fills the screen. The picture then is fine. What might be wrong with the TV and how might I fix it.


    Bookmark   November 18, 2005 at 2:13PM
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"per bullvw - There is also a article at
that lists the most common parts replaced by Philips techs on a dead L01.1 chassis."

Here is the article (note that the below article speaks directly to of the L01.1A chassis for a 29" model, not the L01.1U chassis for the 27" model):

Philips L01.1A chassis
I am beginning to see a few late-model 29PT2255/79R and 29PT2252/79R Philips TVs. I am talking about the L01.1A chassis, which came onto the market about 2001 onwards. The usual problem is that the set is dead due to the fact that the switchmode power supply is cactus.

The cause is not yet fully understood but this fault normally occurs during power surges. To fix it, I order and install what I call "Fred's Mod Kit", named after a friend of mine who repairs these sets under warranty. He found that eight parts usually need replacing - the chopper transistor (7521), its driver (7522), IC7520, R3523, R3530, D6523, D6524 and possibly D6525, which is not always fitted.

Of course, strictly speaking, this isn't a modification kit but only a replacement parts list. Perhaps a modification will come out in due course?

Another problem that is occurring is hum in some Philips models. One in particular comes to mind, the model 29PT4873/79R (L9.1A chassis), which can get particularly bad if placed on a resonating wooden table.

The cause is a deflection yoke with vibrating windings and the solution is to remove it and dunk it in Estapol varnish. Beforehand, it is a good idea to mask any areas that might be critical such as where it contacts the picture tube and the three rubber spacers.

The procedure should be repeated three times, allowing it to dry after each dunking before reassembling it onto the tube neck. That should stop the windings from vibrating and fix the problem once and for all.

    Bookmark   November 20, 2005 at 1:05PM
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There appears to be several threads regarding this same problem of needing sevral attempts to power up unit so that it stays on (maybe someone can use this information to come up with a final solution):


MODEL: MS3252S431
CHASSIS: ch L01-1U AC7638
Keyword: Shutdown
SYMPTOM: MS3252S431 ch L01-1U AC7638. horiz squeal at turn on, horiz freq off set shuts down. after sevral attempts to power up unit will come on and usually stay on.
CURE: Checking capacitors in the horizontal drive circiuit the tech found cap 2455 a 47mf25v in hdt circuit defefective. Replacing the device the symptom was cured.- Thanks to DD Mountain View, Ca.

    Bookmark   November 20, 2005 at 1:19PM
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I have a TV Philips Model No. 27PT543S37A chassis L01.1u it has no audio at all, the picture is perfect, I have tried to hook it up to my surround systems, I checked the menu to see if the speakers were turned off but they are not. Your help will be appreciated

    Bookmark   January 28, 2007 at 8:05PM
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I have a 27" Phillips TV model No. 27PT543S37A chassis L01.1U I have had it for about 5years now, and until last year it was working fine. It started as having trouble turning on it would start then shut off several times really fast, then completely shut off it would take about 3 or 4 times of turning the tv on before it would work. When it come on the image would shake, eventually it turned into taking about 3-7minutes to get the tv on and another 3-4 minutes for the image to slowly creep back from the middle of screen after that it would work fine. Now the tv will not turn on at all and when plugged in it makes a humming and a beeping sound.
Please help me because I really don't want to get a new tv.

    Bookmark   July 23, 2008 at 3:50PM
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i have the same set as Shirou and i am having the same problem. has anyone found a fix for it?

    Bookmark   August 8, 2008 at 2:52PM
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i replaced 7460 and it was back to where the picture would slowly work its way to the edges again. then after about 5 minutes the tweet tweet game back and no picture. anyone have any ideas?

    Bookmark   August 18, 2008 at 3:27PM
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A friend of mine is about to throw his DEAD Magnavox 32" TV and he asked me if I want to take it. Since I have a been repairing TV's back then, I decided to take it and found out that this Magnavox brand is using the same Phillips L01.1 chassis. I got the service manual from the link below, download the 5 compressed files:

Problem: Dead Set (chirping sound when plug to AC outlet)

Solution #1: replaced 7460 (BU4508DX horizontal transistor)
Result: power is up for 2-3 seconds then it shuts down automatically.

Solution #2: replaced 2455 (47uf/25v pol. electrolytic cap)
Result: YEHEY, i got a working 32" TV now.

COST of my 32" TV:
Dead TV = $0.00 (free)
BU4508DX = $14.00 (local electronic store)
47uf/25v cap = $0.99 (fry's electronic)

- use a replacement capacitor with the correct voltage
- i read from other post that BU4508DX is the same as BU2508DX which is the same as NTE2353 that you can buy from fyr's for $7.00
- I guess it's normal for these series of TV's to display raster after 3 seconds, any violent reaction??????

    Bookmark   September 5, 2008 at 5:06PM
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