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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 | ||
| 214168 | 2004-02-09 23:05:00 | Here’s a guessing game for all you up with it techs. I’ve inherited this Philips 14inch TV (model 14pt1482/79R) which has been deemed not worth repairing by the local experts. The problem is that it has something breaking down and blowing fuses. Now I’ve come across an unmarked object in the power supply section of the motherboard which was testing as a full short-circuit. (It appears to be something to do with the degaussing circuitry) Having unsoldered it, it now tests 8 ohms if measured with my faithful Avo or 32 ohms if measured with my Dick Smith Digital multimeter. The resistance measurement across the holes left in the motherboard because of its removal is infinity, which leads me to suspect the heat from the unsoldering may have changed its resistance value. Anyway, the question is what exactly is this unmarked, unnamed object? Its physical appearance is disc shaped, slightly smaller and thicker than an old one-cent piece. It is oxide red in colour and has only the two leads. The resistance is as above and reversing the test leads makes no difference to the reading. Unfortunately there is no label or markings on it, or the motherboard from whence it came. Bit of a tricky one but I’m sure some of you can make a calculated guess. ;) |
B.M. (505) | ||
| 214169 | 2004-02-09 23:17:00 | A thermister ? Enables the de-gausing at switch on by allowing AC onto the degausing coil, then tapering the voltage off. They are normally pretty dependable beasties, unless the coil gets a shorted turn or two. | R2x1 (4628) | ||
| 214170 | 2004-02-10 01:41:00 | Probably a s/c varistor from your description. But then Philips don't usually fit varistors. But some techs do during repairs. I do. OldEric |
OldEric (3062) | ||
| 214171 | 2004-02-10 02:09:00 | If it is a thermister, it should read low coninuity when cold, high when hot. If you are worried, try it without. Be prepaired to power of in case thats not what it is. Sounds about right, and typically it doesn't run anything except the degausing, which degauses on start up for as long as the TM takes to heat up (1-2 Seconds). I wish we had reverse thermistors in computers to slow the fans down until hot. |
CapnRon (2125) | ||
| 214172 | 2004-02-10 02:21:00 | It might be a PTC (positive temperature coefficient) thermistor for the degausser --- in which case it's in series with the mains and the DG coil. You should be able to decide that with a bit of continuity checking. It might be a surge clipper connected across the mains. That's more likely to be a little genie fuseblower, but they usually fail to open. |
Graham L (2) | ||
| 214173 | 2004-02-10 02:37:00 | It is not a degauss thermistor . ALL Philips CTVs, the degauss thermistor has 3 pins and is coloued white in early sets and black in later ones . If everyone is keen to find out what the part is read off the chassis number off the set back . On the outside . It is a small sticker low down in the centre . . . may read something like PV1 or Anubis or similar . Give me the part circuit reference number off the PC board and if I have that manual I'll look it up . Eric |
OldEric (3062) | ||
| 214174 | 2004-02-10 08:46:00 | Thanks guys, sorry about the delay getting back . Well, the plot thickens . I was happy with the thermistor degaussing explanation until Eric said “Not So” . Continuity testing suggests it is in series with the degaussing coil Graham . Anyway Eric, the chassis number is (I think) SV009845 and a part number some distance away from this “thing”, but not obviously related to any other component, is, 3503 or could it be 3583? . I’m starting to think this “thing” is a red herring anyway and I’m off track . Weren’t the days of Valves and things you understood wonderful? Cheers Bob |
B.M. (505) | ||
| 214175 | 2004-02-10 09:23:00 | Intermittent fuse blowing can be caused by ht and eht finding conduction paths across insulators which support the pcb and over time have become conductive through aging and dust build up etc. When you open and change the fuse the path is temporarily broken but it doesn't take long before it is remade. Look for supporting pegs from the base up to the pcb that are around the line Xmer as big suspects. Also switch it on open in the dark and look for little flashes and listen for small arcs and also you may smell ozone. When it is going give it a good bashing, within reason and see that it is not shock sensitive. Blow out all the dust with compressed air. Good luck. CU Rob. |
zqwerty (97) | ||
| 214176 | 2004-02-10 09:41:00 | >Weren’t the days of Valves and things you understood wonderful? Well, they sure made for a lot of jobs. The good old bright emitter, autofail sets, I was briefly in that line of trade, but sold out when colour came in, too much capital in test gear for a one-man business in the early colour sets, and not enough breakdowns. A colour set rented for a dollar a day then, hasn't kept up with other price rises since then. Sorry, bit OT, but [ bump ] |
R2x1 (4628) | ||
| 214177 | 2004-02-10 09:45:00 | >I’ve inherited this Philips 14inch TV (model 14pt1482/79R) which has been There's your trouble, 14" set, metric programs. Incompatible. |
R2x1 (4628) | ||
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