Philips Matchline Classic
 

I have a 28" Philips 'Classic' model 28PT8773 which still gives perfect picture quality. It is in daily use in my dining room. Recently, it has suddenly started to refuse to go into standby. If I use the standby button on the remote, it mutes the sound. Pressing the volume keys does nor restore the sound. If I switch the set off using the mains on/off switch and then switch it back on, it works perfectly but still won't execute a standby command from the handset.

This is very frustrating and something that I have never experienced before. Can anyone please offer any suggestions? Many thanks.

Re: Philips Matchline Classic
 

According to Euras, replace the standby IC.

Re: Philips Matchline Classic
 

Which chassis is this please ? as it doesn't show up on any of my model number lists, which albeit only go as far as 2004.

Re: Philips Matchline Classic
 

That should be an MD2.21E chassis. Model year probably 1998 or 1999. I think this one uses a series switch FET to switch the +B to the line output stage. Mostly, those FET's fail short when the small ceramic harmonic capacitor across the line output transistor fails. When that's the case, the set refuses to turn on at all, so it might be a (slightly) different problem in that area.

Maybe it's "the standby IC". Unfortunately, there are no details on this in Euras. Maybe the schematic will clear things up.

Re: Philips Matchline Classic
 

Thanks Maarten :thumbsup:

I know this chassis, but cannot find that particular model in any of the Philips model surveys that I have.

The MD2.X does use a Fet in the +B line, and as you say does give an unexpected result and error code when it fails S/C.
I will have to have a look at the schematic.:thumbsup:

Re: Philips Matchline Classic
 

I vaguely recall this problem with a G110. When standby was pressed, the audio would mute and the picture would 'flash' as if the power to the line stage was falling slightly them cycling back on. I seem to recall a diode on the PSU secondary being the cause but it was about 8 years ago now.

Re: Philips Matchline Classic
 

Hi ben :thumbsup:
I still cannot find any reference to that model number anywhere in any of the service data I have :shrug: and I do have a fair size library.
Even a quick search on line draws a blank :wall:

Re: Philips Matchline Classic
 

Euras autocorrects to 28PT8703, I see now. I agree that 28PT8773 likely doesn't exist. Should be the same model year though, so chances are that the chassis MD2.21E is correct.

Re: Philips Matchline Classic
 

Thanks again Maarten :thumbsup:
At first I thought it was just me being a bit thick :laugh1:

Edit: Even 28PT8703 doesn't show up either, 29PT8703 however does, and could be either a MD2.22E or a MD2.25E ;D

Edit 2: 25PT8703 also exists, and is listed as above, either chassis types as per the 29" models

Re: Philips Matchline Classic
 

Euras thinks the 28PT8703 version exists, but given the existance of the 25" and 29" 4:3 versions, both super flat tubes (less flat than the later real flat, but flatter than the 28" flat and square tube) I now have my doubts as well. Not really a reason to have both 28" and 29" versions, unless the 28" is a wide screen model (28PWxxxx).

Maybe Vectamart could confirm the type and chassis from the label on the back? Possibly even taking a picture of it? If correct it would be a bit of a rare set.

Re: Philips Matchline Classic
 

Yes Maarten, it would be nice if the OP (Vectamart) came back and clarified the model number, and preferably the chassis type (with a photo of said label), I must say I am somewhat intrigued, and not just about the fault either ;D.

Re: Philips Matchline Classic
 

I'm rather intrigued as well. So much that I'm still pondering so I'll share my latest thoughts... A 28" 4:3 set would have a far better than average survival rate, so that increases the likelihood that this really is one. Most 28" 16:9 and 29" 4:3 sets will have gone to the tip years ago; their ESF picture tubes weren't very long lived.

Re: Philips Matchline Classic
 

A picture of the chassis would also help.

Re: Philips Matchline Classic
 

Gentlemen - many thanks for the responses thus far. The model number that I quoted is per the label on the back of the set. I must confess that all my own searches for the chassis type drew a blank and when I 'Googled' the model number, that also drew a blank so I dragged the set right out and re-checked and the writing on the label is slightly smudged. I have come to the conclusion that the model number may actually be 28PT6773/05R. The set is very heavy and not easy to manhandle so I thought I would try and glean some idea of the likely cause of the problem before delving in.

Re: Philips Matchline Classic
 

Further to my earlier post, I have 'Googled' the alternative model number of 28PT6773 and have come up with a possible solution, viz, "R3588 3R3 ½w o/c in st/by prot cct on large sigs panel - also replace C2561 with 3,300µ 16v".
I will have to bite the bullet and carry the set out to the workshop and see if the recommended treatment does the trick.

The trouble with so many of these late model sets is that they can be extremely awkward to work on! Give me a nice easy G11 to work on any day!

Re: Philips Matchline Classic
 

The 6773 is certainly a valid model number....I think an MD1.2 chassis (it's well over 10 years since I was at Philips and even longer since I worked on one of these so the memory is a little hazy....). Having said that, the MD1.2 chassis (if it is that) is fairly easy to work on. PLEASE lets have some pictures of the internals otherwise we'll be here forever trying to establish just what it is you have!

Incidentally that solution to your fault seems to ring a very distant bell somewhere......

Re: Philips Matchline Classic
 

The internals will correspond to the chassis type, which is also on the type label in a box with a bold S in front of it.

The chassis is almost certainly an MD1.2E AA, which is indeed a good one to work on.

The fix with R3588 and C2561 seems plausible, so measuring R3588 for open circuit would be a very good start.

Re: Philips Matchline Classic
 

I've rechecked the label and it does appear to be an MD1.2E AA chassis. When I have an opportunity, I will take the set out to the workshop and apply the fixes recommended. Update to follow soonest.

Re: Philips Matchline Classic
 

Well, this morning I finally put this set on the bench. The first job was to work out how to gain access to both sides of the large signals panel, given that I did not have a service manual for this model and had hitherto never had occasion to work on this chassis. However, it wasn't too bad. I managed to locate and replace the offending resistor R3588, which was indeed o/c.

The hardest part of all was re-fitting the rear protective cover. Why on earth do the manufacturers have to make this task so damn difficult? In the old days of K30s, all we had to do was to remove and refit two screws, which took about 30 seconds to do. With this set however, there must have been about a dozen or more torx screws, all recessed and a plastic cabinet that keeps flexing every time you try to locate the cover. Am I glad that I don't have to do this for a living any more!

I am happy to report that the TV is now working as good as new and is once more gracing my dining room.

Re: Philips Matchline Classic
 

Another one saved - fantastic news!