Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Champ_49 on October 23, 2015, 01:44:35 pm
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So I have ordered a pair of LED lamps as I had installed the standard Fender lamp assembly that connects to the 6.3V heaters. My question is would these work? I know I should have asked before ordering but in my haste I didn't
https://www.superbrightleds.com/moreinfo/ba9s-ba7s/ba9s-led-bulb-1-led-ba9s-retrofit-car/4/ (https://www.superbrightleds.com/moreinfo/ba9s-ba7s/ba9s-led-bulb-1-led-ba9s-retrofit-car/4/)
The reason I ask is the 6V version of this lamp (which is the one I got) has a current draw of 18mA. I have seen that the original lamp I have has a current draw of 150mA,
I really don't know what they you mean by current draw. Can I think of it as a maximum amount of allowable current before the LED goes POP?
In that case I would have to add some kind of dropping resistor between the heater winding and the lamp?
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If they will fit the lamp socket they should work. I prefer these for 6.3v operation...
http://www.ebay.com/itm/111335488111?_trksid=p2060353.m1438.l2649&var=410349460920&ssPageName=STRK%3AMEBIDX%3AIT (http://www.ebay.com/itm/111335488111?_trksid=p2060353.m1438.l2649&var=410349460920&ssPageName=STRK%3AMEBIDX%3AIT)
The reason I ask is the 6V version of this lamp (which is the one I got) has a current draw of 18mA. I have seen that the original lamp I have has a current draw of 150mA
That LED only uses about a tenth of the electricity that the incandescent lamp uses. Saves money, runs cooler, lasts a loooong time. It has all the same advantages that a household LED light bulb has.
Can I think of it as a maximum amount of allowable current before the LED goes POP?
In that case I would have to add some kind of dropping resistor between the heater winding and the lamp?
No. The 18ma is just the current it will operate at if you connect it to 6V. A resistor is always required with a LED but the resistor is built into the case on that lamp so you're covered.
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Thanks Sluckey for the explanation and the link.
I will try ordering them as well :)
Jay
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I am replacing many of the incandescent lamps in my house with LEDs.
If rated by *Voltage*, you just screw them in. 120V LED goes where I took out a 120V incandescent. 6V LED goes where a 6V incandescent was (or could have been).
Because the LED is much more efficient, it will "pull" less electricity at the rated voltage. Since it is rated for Voltage, you know it won't "pull" any more current than it is designed to. (A bare-naked LED might suck all it can get; these voltage-rated LEDs have some form of current limiter to keep them at the design current.)
An incandescent is a 1-inch hole in your electric bill (leaks electricity, thus money). An LED of similar brightness is maybe a half-inch hole in your electric bill.
I can see the lower power consumption on my electric meter.
Little sub-Watt lamps, it is not about the electric bill. In this case, your amp's power transformer runs insignificantly easier (cooler).
The easier transformer load is unimportant (Whole stock amplifier is say 60 Watts total demand, the LED swap makes it 59.6 Watts, no real difference.) Of course the killer advantage is that LEDs *don't burn out*. (Well not in few-hour/day service, for an amp or a house we may re-re-model or sell-off in 20 or 30 years.) That means NOT going up the ladder "ever again". Or not standing on a dim stage wondering if the amp is sick or the bar's wall outlets, or if it is just a blown pilot light.
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The LED voltage should be below 6 volts
It does not matter what the voltage is under the supply voltage
You always have to use a current limiting resistor with LED's
Use my current limiter calculator here
http://www.el34world.com/php/LedCurrent/LedCurrent.htm (http://www.el34world.com/php/LedCurrent/LedCurrent.htm)]
Go to this page to use my handy current limiter resistor calculator
I stock a nice one with a chrome bezel on this page
http://hoffmanamps.com/MyStore/catalog/LampsMobile.htm (http://hoffmanamps.com/MyStore/catalog/LampsMobile.htm)
Led assembly used for amp pilot light
Maximum panel thickness is 6 mm
Runs off of the 6.3 volt AC heater supply
Long lead is anode (+) in case you are using it on a DC power source.
Lead does not matter for AC power source.
Use a 1/2 watt 180 ohm metal film resistor in line with one of the leads for 6.3 volt Ac use.
Mounts a 1/4 inch hole. Nice chrome bezel around Red LED.
Specs: 1.7 volts at 20ma current rating. Maximum operating current = 40 ma.
Formula for current limiting resistor: 6.3v supply - 1.7 volts = 4.60 volts to be dropped across current limiting resistor.
4.6 volts divided by .02 (20ma) = 230 ohms. 180 ohms will give you about 25ma of current.
Go to this page to use my handy current limiter resistor calculator (http://www.el34world.com/php/LedCurrent/LedCurrent.htm)
(http://hoffmanamps.com/MyStore/catalog/images/IMG_2308.jpg)
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A LED is a Light emitting Diode
Key word here is diode :icon_biggrin:
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This is probably a dumb comment, LED's are typically DC components, and the 6.3 volt wiring on most amps are AC, will there be a problem? I would check to see if the lamp is marked 6.3v AC
Dr Gonzo
The LED's I have seen have a rather low reverse breakdown voltage. Running one on 6.3 VAC is OK, but you have to be careful above that. In one of my projects I powered an LED from a 12.6 VAC filament supply. In addition to the current limiting resistor, I added a regular diode (1N4007 or suchlike) anti-parallel to the LED to prevent the reverse voltage from damaging it.
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You have to use a current limiting resistor
I have never had a problem running LED's is you set the max current around 20 ma with the current limiting resistor
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> You have to use a current limiting resistor
The part he is looking at is not a naked LED, but a "bulb replacement" with base, specified for 6V DC or AC.
See attached.
I have to assume it includes current-limit, and possibly rectification.
Same as the "LED" lamps I am screwing-in all over my house have all that stuff included.
Yes, naked LEDs need current limiting (resistor is simple) and the AC case must be considered (current won't be what you figured, and flicker may be brutal).
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Yes, naked LEDs need current limiting (resistor is simple) and the AC case must be considered (current won't be what you figured, and flicker may be brutal).
I have seen flicker on some LED's in other circuits using AC
No flickering on any of the amps I have installed my chrome bezel LED and 6.3vac
Still running the same amps with the same LED's since late 90's
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Hey all. Thanks so much for all the helpful replies. Yup I figured that the bulb replacement would be like swapping out the bulbs in the house. I guess I'll have to plug it in and see what happens.
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Ok. Thought I'd update you all. The LED that I purchased worked out great. Didn't explode or blow up haha.
I also ordered some pin ball LED's that were suggested to me from here on ebay. Going to try out these ones that change color. Neat.
Also got some other solid colored ones.
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Good deal :icon_biggrin: