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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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17th Feb 2020, 3:27 pm | #1 |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Replacement bulbs with LED question
I have been given a lovely little PPM unit and I've got a a question which someone may be able to answer for me.
Firstly the light bulbs for the illuminated display have blown. To what I can see the bulbs are rated at 6.5v 300mv. There are 4 bulbs all together, all of which have blown. Would you be able to advise me to which LED bulbs would work in it? Many thanks |
17th Feb 2020, 3:48 pm | #2 |
Heptode
Join Date: May 2006
Location: Accrington, Lancashire, UK.
Posts: 977
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Re: Replacement bulbs with LED question
Sorry, just a minor point, it's ma. For dial lights that sounds a tad high though
And sorry, whats a ppm, probably the right name, it's me a bit lacking. |
17th Feb 2020, 3:59 pm | #3 |
Hexode
Join Date: Mar 2008
Location: Bristol, UK.
Posts: 388
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Re: Replacement bulbs with LED question
Probably in the wrong section-not a vintage radio at all.Les
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17th Feb 2020, 3:59 pm | #4 |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Re: Replacement bulbs with LED question
Hi.
It's a peak meter, like a VU meter. Sorry, yes, it's mA. |
17th Feb 2020, 4:00 pm | #5 |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Re: Replacement bulbs with LED question
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17th Feb 2020, 4:13 pm | #6 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
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Re: Replacement bulbs with LED question
If they're MES screw fit bulbs why not just replace them? Would be a lot more authentic than an LED conversion. Spiratronics sell a pack of 5 for £2.90 inc postage.
Alan |
17th Feb 2020, 4:20 pm | #7 |
Hexode
Join Date: Oct 2010
Location: Sandiway, Cheshire, UK.
Posts: 323
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Re: Replacement bulbs with LED question
Four bulbs does seem an awful lot of light for a panel meter and presumably generate a relatively large amount of heat so changing to LEDs make sense.
LEDs radiate illumination basically in one direction, whereas a incandesent filament radiates in all directions. Replacing a bulb with a LED is not always straightforward and you will need to work out how the light from a LED is going to end up where it meant to be. Ian If this 'ppm unit' has a moving coil meter |
17th Feb 2020, 4:24 pm | #8 |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Re: Replacement bulbs with LED question
Thanks... so long as the LED fires forward at the very least then that would be fine.
I can't seem to find a direct drop in LED replacement. |
17th Feb 2020, 5:40 pm | #9 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
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Re: Replacement bulbs with LED question
https://www.ebay.co.uk/itm/4pcs-E10-...MAAOSw~p5crDgv
Should be close enough at 6V but perhaps I'm missing something. Alan |
17th Feb 2020, 6:15 pm | #10 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
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Re: Replacement bulbs with LED question
sometimes dial lights are wired in series, or sometimes from a higher voltage than required with a dropper resistor on the board. I would make sure of how everything is supplied before just shoving LEDs in.
As an example there is an old audio amp I'm familiar with that uses 2 bulbs per VU meter and another in the power switch. They are all series connected across the DC bus with a shunt resistor across the power switch (which uses a smaller bulb) and a series resistor across the whole chain. Maybe I'm muddying the waters but forewarned is forearmed
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Kevin |
17th Feb 2020, 6:15 pm | #11 |
Guest
Posts: n/a
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Re: Replacement bulbs with LED question
If this is AC LEDs will flicker annoyingly. Get real bulbs, maybe 6V 60mA types, available from all good bicycle shops and run cooler than 300mA ones. Should be enough light.
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17th Feb 2020, 6:17 pm | #12 |
Guest
Posts: n/a
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Re: Replacement bulbs with LED question
Valid point Kevin, I would suggest the OP checks each bulb, at least with a filament type you can see if the filament is intact.
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17th Feb 2020, 7:05 pm | #13 | |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Re: Replacement bulbs with LED question
Quote:
I've attached a picture. Hope you can see it. |
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17th Feb 2020, 7:58 pm | #14 |
Guest
Posts: n/a
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Re: Replacement bulbs with LED question
They are in series, is there (as suggested by McMurdo) a series resistor too? A picture of where the wires go to will help.
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17th Feb 2020, 8:39 pm | #15 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,676
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Re: Replacement bulbs with LED question
Have we confirmed that they are MES bases? It's not obvious that they are from the picture.
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17th Feb 2020, 9:00 pm | #16 |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Re: Replacement bulbs with LED question
Some more pics for you.
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17th Feb 2020, 9:01 pm | #17 |
Tetrode
Join Date: Aug 2009
Location: Derbyshire, UK.
Posts: 50
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Re: Replacement bulbs with LED question
Oh.. and I found these too.
I emailed the company and they suggested they might work https://internationallamps.co.uk/pro...e10-mes-white/ |
17th Feb 2020, 9:17 pm | #18 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
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Re: Replacement bulbs with LED question
Given the size of the unit, it'll hardly run hot as is. If they're too bright, add a series resistor in the chain. 22 ohm 2.5W would do nicely. The bulbs will probably last for ever too being underrun by about 20%.
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17th Feb 2020, 10:19 pm | #19 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
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Re: Replacement bulbs with LED question
There's something not quite right about all of this. The bulbs look like they're connected to an output of the PSU rated at 18V and .28A. Four series connected bulbs marked 6.3V at .3A each doesn't make much sense unless I'm completely misinterpreting the arrangement. As the unit has an unknown history I'm wondering whether or not someone's previously fitted the wrong bulbs. Does it otherwise work correctly? I know the bulbs don't work but have you tested each of them for continuity or can you see that the filaments have broken?
Alan |
17th Feb 2020, 10:50 pm | #20 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
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Re: Replacement bulbs with LED question
Knowing the make and model would help too as someone might be able to track down a circuit diagram.
Alan |