Tuning scale lamp for a Sansui tuner - advice needed

[REW]

I bought a Sansui TU-S5 tuner as much for its looks as anything, as it has to live in the lounge and be easy on the eye. It worked well for a day then the bulb that illuminates the edge of the tuning scale failed and some of the beauty has gone, dammit.

Trouble is replacing it - I am unclear what its voltage is and then its wattage. My volt meter says 20v AC across the poles of the power supply that feeds it, but 1v DC as well. How can this be? What is the bulb type? I attach some pix and if any one can shed some light (haha) on this I would be grateful.

http://i76.photobucket.com/albums/j38/REW27/Sansui%20TU-S5%20Tuner/Panelbulb_zps38998913.jpg (http://s76.photobucket.com/user/REW27/media/Sansui%20TU-S5%20Tuner/Panelbulb_zps38998913.jpg.html)

The broken filament can clearly be seen. Sometimes with a suitable tap I get it to light again briefly. It is about 4mm diameter by about 10mm plus a bit of silicone sheathing.

With light on:

http://i76.photobucket.com/albums/j38/REW27/Sansui%20TU-S5%20Tuner/Panellit_zps18d8ff82.jpg (http://s76.photobucket.com/user/REW27/media/Sansui%20TU-S5%20Tuner/Panellit_zps18d8ff82.jpg.html)

and other lights:

http://i76.photobucket.com/albums/j38/REW27/Sansui%20TU-S5%20Tuner/Notlit_zpsccd74456.jpg (http://s76.photobucket.com/user/REW27/media/Sansui%20TU-S5%20Tuner/Notlit_zpsccd74456.jpg.html)

[The Grand Wazoo]

Hi Ron,
The AoS search function is a great tool.
Take a lookee here (http://theartofsound.net/forum/showthread.php?6253-Sansui-TU-517-display-bulb-wanted) at this old AoS thread for some links to a few suppliers - knowledgable people, who I'm sure will know what value you need.

Good luck!

[REW]

Thanks Chris - hadn't thought of eBay Germany. Will have a look.

My Rotel service manual quoted voltage and wattage which made sourcing similar items easier. The Sansui service manual just quotes a possible part number so finding similar specced items is trickier. This tuner is not one of the classics so I guess that adds a little spice to the hunt.

[istari_knight]

Is it this sort of thing ? http://www.ebay.co.uk/itm/Lampen-lamps-24-V-35-mA-4-5mm-CAS-/400060025420?pt=DE_TV_Video_Audio_Einzelteile&hash=item5d256f8a4c

[REW]

It certainly is James, thanks. My lamp measured accurately is 4mm diameter by 9.5mm length of glass envelope, but the ones you link to would fit well. My knowledge of electronics is pitifully small, as you can see from my attempt to establish the supply voltage! So, question is, would a 24v bulb be AC, DC or does it matter?

[REW]

And Google is my friend. Apparently an incandescent bulb will run off either AC or DC: http://uk.answers.yahoo.com/question/index?qid=20100911112830AANp90Z I will ask the supplier what he thinks James.

[istari_knight]

Sorry, only just seen your reply.

I've always found CAS to be very knowledgable. Give them the dimensions + working voltage & see what they recommend.

[REW]

CAS hasn't replied yet but I wandered into Maplins yesterday and discovered Lilliput Edison Screw base filament lamps! Had no idea they existed. They are 5mm diameter and fit a simple holder that fits with little alteration the space in the display on my tuner occupied by the standard bulb. The effect is as seen in this (crappy) photo:

http://i76.photobucket.com/albums/j38/REW27/Sansui%20TU-S5%20Tuner/Nightlights_zps8d15d52b.jpg (http://s76.photobucket.com/user/REW27/media/Sansui%20TU-S5%20Tuner/Nightlights_zps8d15d52b.jpg.html)

The bulb is 24v 40mA and so just under 1w but with just 20v it must be less (about 0.8w). It could usefully be a touch brighter and I note 1.1, 1.2 and 1.5w versions are out there to experiment with one day. So panel lamps you can't get can be substituted by these little fellas, in a variety of voltages too. They are small and easy to place. Maplins: http://www.maplin.co.uk/p/24v-lilliput-les-bulb-bu16s

Thanks for all the advice folks. If CAS reply I will share info.

[Naughty Nigel]

I have similar lamps in an old Yamaha amplifier and tuner; some of which have also blown! These are fitted in green silicone sleeves (to give a green light), and I believe are 12 volts, but I can check. It is unlikely that Sansui would have used a non-standard voltage.

Unlike LED's, incandescent bulbs will work on either AC or DC. The voltage that you measured at the transformer is probably without any load. The voltage under load (i.e. with the lamps working) will be lower.

However, if necessary, you could use a 12 volt bulb with a series resistor to reduce the voltage at the bulb. Instrument bulbs will have the longest working life, and are available from CPC.

LED's could also be used, but you would need a rectifier and current limiting resistors. The quality of light provided by LED's is also unsuitable in many cases.

Nigel.

PS: I have just thought, you might be able to use some old Christmas tree lamps, as these are about the right size, and are nearly always 12 volts. The older Christmas tree lights were indeed Edison Screw! Just make sure you don't use the flashing bulb! :)

[REW]

Just spotted your reply Nigel, thanks. Yes, the voltage drops to about 16v when I use the 24v LES bulb. I am going to try two bulbs in parallel to get the right degree of illumination, two at 14v for example, so the voltage drop works for me. The bulb life is between 5 and 10,000 hours so that should do.

CPC? Who are they please?

Christmas lights are indeed LES but have a long bulb, so won't fit my situation. Mind you, a flashing frequency scale would get some attention...

[Firebottle]

It's always a good idea to put a low value resistor in series with these small filament bulbs.
You loose a slight amount of light output but the lifetime is extended very considerably. In fact I don't know of one that has blown since the inclusion of a resistor.

It is the switch on surge into a cold filament that does the damage over time, putting a resistor in series cuts the magnitude of the surge.
Anything between 10 and 47 ohms should be suitable.

:cool: Alan

[Naughty Nigel]

Just spotted your reply Nigel, thanks. Yes, the voltage drops to about 16v when I use the 24v LES bulb. I am going to try two bulbs in parallel to get the right degree of illumination, two at 14v for example, so the voltage drop works for me. The bulb life is between 5 and 10,000 hours so that should do.

CPC? Who are they please?

Christmas lights are indeed LES but have a long bulb, so won't fit my situation. Mind you, a flashing frequency scale would get some attention...

For CPC try http://cpc.farnell.com/

Nigel