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Post by brigham on Apr 25, 2017 10:02:24 GMT
Are those lamps a standard fit base? So that you could inadvertently insert a green lamp in a red socket? It would certainly assist Ronnie Biggs-type operations! |
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Post by trt on Apr 25, 2017 10:11:57 GMT
Are those lamps a standard fit base? So that you could inadvertently insert a green lamp in a red socket? It would certainly assist Ronnie Biggs-type operations! That never occurred to me. One can see how YOUR mind operates.  |
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rincew1nd
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Post by rincew1nd on Apr 25, 2017 10:56:27 GMT
It looks like the pins are different, based solely on the above photos.
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rincew1nd
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Post by rincew1nd on Apr 25, 2017 10:57:32 GMT
Using a combination of red and green LEDs in what looks like a single aspect head allows three aspects to be shown to the driver as red and green together produce yellow. This sounds a good recipe for "wrong side" failures. If the red LEDs fail a "caution" aspect would appear to be "all clear" Surely though the lamp proving would detect the failure though and thus prevent a train approaching the signal. |
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Post by norbitonflyer on Apr 25, 2017 11:04:56 GMT
It looks like the pins are different, based solely on the above photos. They look identical to me. Has anyone got an end-on view? Is there anything in traditional signal heads to prevent a green lens being put where a red one should go? |
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Post by trt on Apr 25, 2017 12:06:11 GMT
It looks like the pins are different, based solely on the above photos. They look identical to me. Has anyone got an end-on view? Is there anything in traditional signal heads to prevent a green lens being put where a red one should go? I thought the lenses had moulded bumps on them which engaged with slots in the retaining ring. Although, TBH, I've only played around with the one old signal head that my grandfather had in his garage, and God alone knows where he picked that up from - probably one of the forces railway depots from his days in the Signals. I believe he was based near Bicester for a while upon returning from Germany. |
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Deleted
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Post by Deleted on Apr 25, 2017 13:00:42 GMT
Are those lamps a standard fit base? So that you could inadvertently insert a green lamp in a red socket? Correct and it has been done |
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Deleted
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Post by Deleted on Apr 25, 2017 13:01:14 GMT
It looks like the pins are different, based solely on the above photos. They look identical to me. Has anyone got an end-on view? Is there anything in traditional signal heads to prevent a green lens being put where a red one should go? No |
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Post by trt on Apr 25, 2017 13:05:36 GMT
Are those lamps a standard fit base? So that you could inadvertently insert a green lamp in a red socket? Correct and it has been done So the controls for preventing this sort of mishap are procedural rather than technical? Or do the lamps have some sort of electronic difference, like the CAN bus versions of automotive lamps? |
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cso
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Post by cso on Apr 25, 2017 13:10:21 GMT
Are those lamps a standard fit base? So that you could inadvertently insert a green lamp in a red socket? Correct and it has been done One would hope that would be caught in "post change" testing before a train discovered it... |
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Deleted
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Post by Deleted on Apr 25, 2017 14:00:53 GMT
Correct and it has been done So the controls for preventing this sort of mishap are procedural rather than technical? Or do the lamps have some sort of electronic difference, like the CAN bus versions of automotive lamps? Apart from the colour of the actual LED's there is no difference it's all done by a rigous procedure in the form of a authority to work certificate better known as a AWC |
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Deleted
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Post by Deleted on Apr 25, 2017 14:03:10 GMT
Correct and it has been done One would hope that would be caught in "post change" testing before a train discovered it... It actually happened at Whitechapel when they were first installed and the green and red were swapped by mistake. Driver reported signal at danger when the signaller reported showing green on his diagram. A green behind a red lens still shows red and a red behind a green lens shows a orange / red colour |
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Post by tubelightonline on Apr 25, 2017 15:15:43 GMT
Didn't some signal heads require the fitting of lamps with a special three-pin bayonet cap, as a way of ensuring that they could only be installed one way around, in order that the lens focused the lamp filament, and thus the beam itself, correctly? The LED retro-fit examples seen in the earlier post appear to be the standard two-pin bayonet type, though I think that you'd probably realise if you'd installed these the wrong way around when the aspect failed to glow but the interior of the signal head was lit brightly!
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Deleted
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Post by Deleted on Apr 25, 2017 15:37:26 GMT
The ones in the picture are for tunnel heads with small lenses.
The 3 pin lamps / LED's are for the tunnel heads with the large lenses and are a lot bigger to the ones in the picture
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Post by fish7373 on Apr 25, 2017 16:57:05 GMT
The ones in the picture are for tunnel heads with small lenses. The 3 pin lamps / LED's are for the tunnel heads with the large lenses and are a lot bigger to the ones in the picture ![]() ![]() ![]() This is a tunnel signal head from the northern line ![]()    The LEDs lamps have the same size bayonet fittings so you can have them round the wrong way plus the signal head came from the northern line tunnel thanks FISH7373 81C NFP |
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Deleted
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Post by Deleted on Apr 25, 2017 19:17:43 GMT
Them LED's didn't come out of that signal
That is a Short Range signal head it might well of been installed in a tunnel but they are also used for Fog Repeaters in the open. That signal would of had the bigger 3 pin variant
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Post by fish7373 on Apr 25, 2017 21:05:17 GMT
Them LED's didn't come out of that signal That is a Short Range signal head it might well of been installed in a tunnel but they are also used for Fog Repeaters in the open. That signal would of had the bigger 3 pin variant Yes the LEDs came out of that signal head in my office at Northfields depot , and would you like a photo of them fitted to the signal head of the inside.PS or visit me in my offices at Northfields depot for a look. |
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Deleted
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Post by Deleted on Apr 25, 2017 21:56:47 GMT
Wrong type of LED in that signal head or in other words not to standard
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Post by bananaman on Apr 26, 2017 4:32:18 GMT
Are those lamps a standard fit base? So that you could inadvertently insert a green lamp in a red socket? Correct and it has been done As has the fitting of the wrong colour lens in the signal head |
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Post by brigham on Apr 26, 2017 7:40:19 GMT
The two-pin LED clusters are unlikely to light, if put in backwards. They need the correct polarity.
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Deleted
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Post by Deleted on Apr 26, 2017 7:46:45 GMT
That's why they have diodes to force the current one way
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Post by John Tuthill on Apr 26, 2017 7:48:57 GMT
That's why they have diodes to force the current one way The clue is in the name- Light Emitting Diode |
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Post by trt on Apr 26, 2017 10:41:12 GMT
I think the clue is in the fact it is labelled for 80-100V AC. They would light if inserted back to front.
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Post by Dmitri on Apr 26, 2017 16:45:04 GMT
The clue is in the name- Light Emitting Diode Although LEDs are diodes, their maximum reverse voltage is very low, typically 5 V, so they are not normally used as rectifiers. I think the clue is in the fact it is labelled for 80-100V AC. They would light if inserted back to front. They must have a bridge rectifier inside  . |
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Post by fish7373 on Apr 26, 2017 19:37:44 GMT
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Post by trt on Apr 26, 2017 22:54:20 GMT
That's two sockets per lens?
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Post by bananaman on Apr 27, 2017 4:25:10 GMT
Yes, traditionally some signals had a Main lamp and a Standby lamp.
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Post by trt on Apr 27, 2017 6:06:23 GMT
And when fitted with LEDs, you had to put some sort of shunt load in the standby socket?
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Deleted
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Post by Deleted on Apr 27, 2017 6:08:33 GMT
No it's just a blanking piece if a LED was placed in the front holder then the beam of light would not project properly through the lens.
That type of signal should have the bigger version of the LED installed not the tunnel type.
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Post by trt on Apr 27, 2017 7:05:22 GMT
I thought they would have had current detection to pick up blown lamps.
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