led lights

[bingobelle]

Hi

Need help to sort out some things.

First a "short" story what have happened.

I have a jvc jr-s400 receiver. All but two of the original bulbs where burned out so went to a audio shop and bought some new ones. I showed the guy that the fuse types should be 12 v and 150 mA. The small minibulbs where 6 Volts and 35 mA except the one for the dial pionter that is 6 Volt and 100 mA.

Anyway, he told me it does not matter some mA here or there and to be honest I´m not sure what lamp he gave me. The fuse type however I later saw that they where 300 mA so no wonder the fuses for the lamp circuit went after a couple of hours. the small minibulbs I´m not sure about but I guess they where 70 mA he gave me.

anyway, the minibulb did light very week and after looking some time on the circuit diagram I think I underdstand why, the minibulbs is connected in series with resistors becuase they are fed by the same stab circuit as the 12 volt fuse type lamps. So they have to have the correct mA because as I understand a for example a 70 mA 6 volt bulb have less resistance compared to a 6 Volt 35 mA bulb. So the correct bulb is very important to obtain the correct voltage drop over the bulb.

So the voltage over my bulb where only 4,5 Volt instead of 6 volt. hence the weak light.

Now to my question, instead of looking further for some other incandescent bulb I bought a led kit for my receiver on ebay.

I mounted the 4 fusetype led lamps and the 3 led minibulbs. all work but as I was worried about it is very brigtht. the small mini led acording to sellers store on ebay is made for 6 to 8 volt and the fuse type lamps ois made for 12 volt.

However, I measured the voltage now over the small led bulbs and the voltage is 10 volt. So as I understand it the resistance of those led lights is much higher compared to the original incandescent bulbs. So over the resistors it is now only 1,12 volt.

So, how will this affect the life expectancy of the led bulbs? 10 volt on a 6 to 8 volt led bulb?

also, how come it does not matter about the polarity? the led bulbs lights up regardless of what wire leaqd goes to ground or not. If I understand there is a rectifier on the stabilisation board. are those led bulbs that are sold for vintage audio gears some special led bulbs that do not care for polarizxation of the lead wires?

Should I solder in a drop resistor in the wire leads on the small led bulbs?

I did some calculations, should a 820 ohm resistor do the trick to achive about 6 volt over the led?

I attach the circuit diagram.

Now this post is already to long but hopefully someone can give me some hint or explonation.

Sorry for my very bad technical english but I do my best, english is not my native language.


Thanks!

 

[avionic]

he told me it does not matter some mA here or there and to be honest I´m not sure what lamp he gave me

Oh but it does matter... Bulbs that burn to hot have a tendency to melt and deform plastic/rubber lamp holders. I see it all the time..
Contact Dave at dgwojo.com and tell him exactly what you need and Dave will hook you up with the correct lamps for your application.

 

[bingobelle]

Oh but it does matter... Bulbs that burn to hot have a tendency to melt and deform plastic/rubber lamp holders. I see it all the time..
Contact Dave at dgwojo.com and tell him exactly what you need and Dave will hook you up with the correct lamps for your application.

Yes, i learned about Dave after I had ordered this led kit. Anyway, since I live in sweden this ledkit have already cost me 22 dollar with shipping cost and the lamps i bought in sweden that did not work was another 15 dollar so up to this date those lights has costed me silly amount of money for what it is.

so for now I just want to learn how to fix this and if it is something I have misunderstood. for example, is it common that those kind of smal led bulbs sold for vintage receivers have a build in resistor in the shrink tube or in the ledbulb itself? and thats the reason i have 10 volts over the ledlamp?

The strange way that this is engineered imho is that on this receiver they use the same output for both the 6 volt and 12 volt lamps. it should have been better with two transistors or only 6 volts lamp all together. but this was maybe a common way to do, i have no clue.

However, what I´m most interested to know is if I have to adress the fact that I now have 10 volt over my new led bulbs that according to seller is made for 6 to 8 volt. but this ledkit was bought specifically for this jvc receiver.

 

[Semanon]

6 volt lamps on a 10 volt circuit will have a short, unhappy life (but they will have burned bright). By all means, reduce the voltage.

It is hard to say how the lamps were made, but chances are that the seller made some custom lamps for this unit.

Voltages vary between units and drift over time. Put in the new resistor ans be done with it. Be sure to get one with the proper power rating. It may increase with the increased resistance.

Regarding polarity, for the 6V lamps, I'd guess they are receiving AC. The others are getting DC per the schematic.

 

[bingobelle]

6 volt lamps on a 10 volt circuit will have a short, unhappy life (but they will have burned bright). By all means, reduce the voltage.

It is hard to say how the lamps were made, but chances are that the seller made some custom lamps for this unit.

Voltages vary between units and drift over time. Put in the new resistor ans be done with it. Be sure to get one with the proper power rating. It may increase with the increased resistance.

Regarding polarity, for the 6V lamps, I'd guess they are receiving AC. The others are getting DC per the schematic.

I´m pretty sure all the lamps is on dc. Both the 6 volt and 12 volt lamps are fed from the same transistor except the 6 volt bulb indicating stereo on FM broadcasting. the 6 volts bulbs just have some drop resistors in the line. the 6 volt bulb for the dial pointer is also connected in serie after the 12 volts fuse types lamps. My DMM also refuse to give any readings on AC. Must be on DC to have some readings.

I´m not so good at this stuff but the way I see it those mini ledbulbs that have replaced the old 6 volt incansendent bulbs must consist of two light emitting diods in the small bulb house connected in pararell with diffrerent forward bias or what it is called. If not, how can they light up no matter what wire lead goes to common and line? Also I guess there must be a resistor in the wirelead or in the bulbhouse hence the 10 volt drop. A diod will not have 10 volt dropp otherwize if it was only a light emitting diod in the ledbulb. maybe 2 volt or something like that. So proberly everything is ok, after all the seller is a very well known for ledkit to vintage receiver.

The thing is that I´m just currios to know exactly how this might be, always nice to learn something new.

 

[gadget73]

depending how much stuff they want to pack into the bulb, a bridge rectifier setup would force it to light up in either direction. You'd have the voltage drop of the diodes, but it would need to shed some voltage anyway. Bridge + drop resistor would get that done.

or it might just be parallel diodes set up so its one or the other like you said. And a resistor of course.