Need Help Making Sansui 9090db LED Dial Lamps

[vintageradio]

For my Sansui 9090db, I would like to make some LED lamps to replace my old dial lamps.

I am running into a bit of problem: I understand that the voltage on the Sansui 9090db dial lamp circuit is 6.3v. If so, it will be difficult to make a LED lamp using two LED in series as most of the LED I sourced appear to have 3.4 Forward Voltage. (I think two LEDs are needed as one LED is simply too dim). Two of those in series will yield 6.8 FV. The 6.3v circuit will not have sufficient voltage to overcome the forward voltage of 6.8v and light up the LEDs at the same time. Perhaps my understanding is incorrect?

Does anyone make any LED dial lamps for Sansui 9090db? What is your calculation? HELP!!

I also read elsewhere that you need to convert the AC to DC in order for the LED lamps to work. Is that necessary?

 

[DougBrewster]

Depends what you're looking for; quick and easy store bought plug-in fuse lamps or something like the one shown in the link.

http://www.audiokarma.org/forums/showthread.php?t=580749

Google 9090DB LED LAMPS and you'll find some options; for example there are folks on ebay selling festoon or fuse lamps to order which plug right in to the existing main scale lampholders. Looking at them, they only appear to have a rectifier diode and resistor in series with the LEDs in the capsule so they'll be operating on an unregulated supply with a lot of ripple assuming the normal 6.3vac supply hasn't been modded. The claimed 100,000hrs life is valid I think, only when operated with a good regulated, smooth supply. What the life will be with a half wave rectified, un-smoothed and un-regulated supply is anyone's guess (could still be as good as/better than incandescents though). And fuse lamps don't fit into the power meters etc...

Far as operating voltage is concerned, that varies with the current draw. A nominal 3.4V could be as low as 3v or even less if you decide to operate them below full current rating for longer life. It's difficult to see the difference in brightness between running them at 70% and 100% current rating...

 

[Sam Cogley]

Get in touch with AKer CKeeler. He's the LED guru.

 

[vintageradio]

Depends what you're looking for; quick and easy store bought plug-in fuse lamps or something like the one shown in the link.

http://www.audiokarma.org/forums/showthread.php?t=580749

Google 9090DB LED LAMPS and you'll find some options; for example there are folks on ebay selling festoon or fuse lamps to order which plug right in to the existing main scale lampholders. Looking at them, they only appear to have a rectifier diode and resistor in series with the LEDs in the capsule so they'll be operating on an unregulated supply with a lot of ripple assuming the normal 6.3vac supply hasn't been modded. The claimed 100,000hrs life is valid I think, only when operated with a good regulated, smooth supply. What the life will be with a half wave rectified, un-smoothed and un-regulated supply is anyone's guess (could still be as good as/better than incandescents though). And fuse lamps don't fit into the power meters etc...

Far as operating voltage is concerned, that varies with the current draw. A nominal 3.4V could be as low as 3v or even less if you decide to operate them below full current rating for longer life. It's difficult to see the difference in brightness between running them at 70% and 100% current rating...

Thanks for the clarification.
I wanted to make my own LED lamps using SMD LED diodes that I already have. In fact, I made all my LED lamps for my Marantz 2325 using the SMD LED+Resistor. Work real well. It is a fun learning project (they joy of the hobby , not so much to save $$$.

Where I was stuck with my Sansui situation is that, unlike my Marantz 2325 which has a supply voltage of 7.3v (I think), Sansui seems to only have a supply voltage of 6.3v. Based on 6.3v, I am not able to use TWO LED (fv=3.4 each). But, reading your response, my take away is that, I can still use two LEDs and that perhaps they will light up at lessor intensity. Ok, I will give that a try.