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| Thread ID: 42393 | 2004-02-09 23:05:00 | Techs (What is it?) | B.M. (505) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 214178 | 2004-02-10 11:37:00 | Sorry Rob, not dust or tracking as far as I can tell. Damn thing doesn’t look like it’s ever been out of its box. Metric programmes aye R2, I love it. If it weren’t for the fact I’m retired and get a bit bored, I wouldn’t bother trying to fix it, given that even if I manage to do so, there is nothing worth watching and there’s already 4 other working TV’s in the house! Cripes, they keep changing the news readers and I still can’t find Alma Johnson bahhhhh! Moving right along, I decided this unidentified object has probably got sweet ---- all to do with the problem so I donned my “super dooper” magnifying glasses and found what I suspect is a little ceramic capacitor with a black hole in its top. Now this little sod is identified as follows: HR R 331k 1000v and hangs around with a transistor identified as ST W810 P4NA60FI, which is attached to a whopping great heat sink. Now, the resistance of this little beast (the capacitor with a small black hole on top) reads 400 ohms on the old AVO and 2K ohms on the digital. (maybe the digital is metric too) I suspect that with a little more volts applied this little blue beast would submit to short-circuitville and may indeed be the problem. Anyway, I have this urge to replace it, so can anyone suggest where to obtain a HR R 331k 1000v capacitor. I can’t find anything even similar listed with Dicky Smith. Thank you all again for your patience, Bob |
B.M. (505) | ||
| 214179 | 2004-02-10 20:50:00 | Hi Bob . . . well I think you have solved your problem . Those little blue caps are a common failure item showing a little black spot on the casing . But be aware its failure may have damaged the switching transistor (fet) and other circuit components or at best stressed them . Should you change the little blue beast change the other ones too if any more in circuit (depends upon the model) . The value is not too critical . The caps can be obtained from Trade-Tech Auckland and Christchurch . Ph . 09 478 2323 . The trade price is around $3 . 50 each . They are from a different manufacturer . The VDR 3505 is a varistor . It is marked on the circuit diagram but is not listed in the parts list . This indicates that it it is not normally fitted in the NZ market models . Methinks a tech has fitted it during servicing . If you trace the circuit further you will find it is across the mains input . Useless info?? . . . The circuit number . . . 3505 . . . the 3 indicates it is a resistor . . . the 5 indicates iit is the PU . . . the 05 is the cct ref . # . Don't forget the "bite" from the big electro . . . there is no discharge cct fitted . Eric |
OldEric (3062) | ||
| 214180 | 2004-02-10 22:01:00 | Thanks for that Eric . I follow up later as a guy has just turned up with a trailer that needs the lights fixing for a WOF . Wonder what can go wring here? :D |
B.M. (505) | ||
| 214181 | 2004-02-10 23:29:00 | > Thanks for that Eric . Well done OldEric !! Nice to see someone come up with helpful chapter and verse ! Cheers Tony |
TonyF (246) | ||
| 214182 | 2004-02-11 07:34:00 | A little query if I may? My understanding of a varistor is that it has a high resistance, which reduces as the voltage increases . Now, this disk has a resistance of 32ohms if measured (out of circuit) with the Avo and 8 ohms if measured with a digital ohmmeter . Both meters have a test voltage of approximately 3 volts . Eric, I can’t be sure of the origin of this set, but I note it is manufactured in Singapore and I seriously doubt it has ever been to a service centre . I’m sure someone can straighten me out and ease my confusion . :D Bob |
B.M. (505) | ||
| 214183 | 2004-02-11 08:49:00 | I would not expect those low readings from the Varistor. It may be a legacy of a voltage spike that also took out a few other components. If its not fitted for NZ, simply don't put it back in? |
godfather (25) | ||
| 214184 | 2004-02-11 19:08:00 | Hi Bob . . . yes I forgot that you mentioned that your mystery component was reading 8 ohms . The circuit I viewed is a close relative to yours and the part number says it is a varistor . Maybe as GF says leave it out initially . With lightning strikes usually varistors split or go discoloured . It may not be a Varistor, it may be a PTC . This PT series was subject to changes, e . g . there was initially trouble with a zener controliing circuit to the controller chip . To make things more difficult the "parent" board design would not fit physically into a 14" cabinet so circuit changes may have occurred along with physical changes . Looking at other Philips circuits of this era . . . mid, later 90s PTCs were used in 2 designs in the "start up" circuit . These switched mode power units need a "kick" of voltage to start them . Another thought it could be extra current limiting for the degauss PTC after the initial current surge had completed its job . As you see the possibilities start to become endless and it now becomes a guessing game . Yes, Philips sets are made in Singapore for this area, the circuits we use are from the parent Company in Holland hence the listed USA modifications . Eric |
OldEric (3062) | ||
| 214185 | 2004-02-12 04:57:00 | Well team, we now have Raster- Picture & Sound . Replacing the little blue 331k capacitor with a second hand 470k (that tests at 420k) did the trick all right . Just what our unidentified object is exactly I’m still not sure but I can advise the TV works OK without it and it is definitely in the degaussing circuit . (In fact, other than the coil, it’s all that’s in the degaussing circuit) Realistically it would have to be quick off the mark to up its resistance as the degaussing coil only measures 14 ohms and I’m picking its impedance isn’t a hell of a lot more . So, if it didn’t work, or went short circuit, we’d be relying heavily on the fuse to save the day . It still surprises me that Phillips would install unidentified objects or in fact anyone would manufacture something of this nature with no identification . Anyway, we’re away, so thanks to all who helped out . Cheers Bob |
B.M. (505) | ||
| 214186 | 2004-02-12 05:03:00 | Mr Philips knows what it is. And his equipment never fails. :D | Graham L (2) | ||
| 214187 | 2004-02-12 05:26:00 | Varistors come in two flavours..PTC and NTC NTC is Negative Temperature Coefficient which means as the temp increases, so the resistance falls. PTC is Positive Temperature Coefficient which means as the temp increases, so the resistance increases. For the Degauss circuit, a PTC is used so as the current rushes through the coil, it heats the PTC, so increasing the resistance, so eventually stopping (basically) the current through the coil. So degaussing the TV set on "cold" switch-on and getting rid of minor magnetic effects that can discolour the picture. I suspect the un-named device is a PTC that limits any current in-rush. Hence it may be low resistance. To test, measure the resistance,while hold it over a soldering iron and see if the resistance increases. I think I have it right. :) |
Pheonix (280) | ||
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