1176 incandescents to LEDs

Anyone ever retrofit a vintage 1176 from incandescents to LEDs? Im thinking its probably not to involved, all you'd need to do would be to rectify the AC and just pop in some LED's, but this is way outside the realm of my knowledge, so maybe its way more complicated... It probably is, everything I think will be easy turns out to be underestimated...

Anyhow, anyone have any ideas here? I know that andrew did this with the mc76, I wonder if there are any published circuits out there. Got three old 1176 that I would like to change from the bulbs to LEDs.

dave

don't even need to rectify to DC since it's a diode anyway(it'll just work on the half cycle).. what voltage are you going to run the leds from? use ohms law to figure your resistor based on what your LED needs. simple as that.

good luck!

I can just hook up some LED's and resistors to the AC lines that were meant to power the bulbs? A gremlin wont pop up and have a havoc party inside my 1176?

Seems like there would be more to it than that.

dave

just make sure the anodes/cathodes face the same way and you should be golden. if you must, you can use a small bridge and solder the leds/resistors to it..

I have a small schem for this..

from when I did the bloo 1176's

arrays 20 3mm LED's across the top... no gerber but im sure it wouldnt be too difficult to come up with

I'll look for it tonight

scenaria-

let me know if you find it...

dave

Either:

Use a bridge rectifier (and a capacitor if you like... extra brightness since it keeps the LED brightness at max, rather tne spending most of the time below peak brightness) and solder a chain of LEDs and a current-limiting resistor between the [+] and [-] terminals,

or:

Use a current-limiting resistor feeding two chains of LEDs, each chain in series, all pointing the same way (i.e. anodes soldered to cathodes), but with the two chains in parallel, but pointing in opposite directions. It's also even better if you join each 'rung' on this ladder.

but *DO NOT* rely on the 'it only conducts one way' notion... here's why:

An LED will conduct in one direction to try to maintain a forward drop of-say-2 Volts. That's fine. But a reverse voltage causes the LED to stop conducting, and that puts the entire voltage across the junction. If you're talking about 30V RMS, that's about 42V peak reverse bias, at the point when the voltage i sswinging the 'other way'. -An LED won't like that, and its life may well be seriously shortened. -Connecting a second LED backwards in parallel across it will limit the reverse bias voltage to to equal the forward bias of the other LED... so our reverse-biased LEDs each only see 2V reverse voltage.... much better.

Keith

thank you guys for the info! I wont get to this for a few days, but at least now I can offficially put it on the "to do" list.

I called UA earlier to try to purchase a bezel, perhaps the most unhelpful company I have dealt with in quite some time.

Does anyone know if those meter bezels are available seperately in the world or am I stuck buying an entire new meter assembly? What the hell fits the cut out on that panel?

what did you use scenaria?

dave

i got some packaged 120VAC leds and i cut one open.. ok so i forgot a part!, one resistor, the led and a diode, 1n4004. both the led and the diode cathodes are the same direction.. so it goes resistor, anode(led) cathode-anode(diode) cathode..

I used meters from andrew over at purple audio...

by the way he sells LED light kits for the meters... I think they are $30

not bad considering all you do is drop in a few screws and wire it in... nice even glow

heres the thing with bezels... when meters are ordered from the manufacturer they only allocate one bezel per meter.. soo its kind of like me with parting out LA2 kits... you sell someone a bezel and you have a meter that has none... :\

this is why your forced to get the meter and all...

The ones from purple are Hoyt meters... pretty nice IMHO... BUT they are like $95 each

[quote author="Svart"]i got some packaged 120VAC leds and i cut one open.. ok so i forgot a part!, one resistor, the led and a diode, 1n4004. both the led and the diode cathodes are the same direction.. so it goes resistor, anode(led) cathode-anode(diode) cathode..[/quote]

..or that's a third way. the reverse voltage of a 1N4004 is 200V, so that blocks the reverse to protect the LED and stop if from taking the hit...

Keith

[quote author="soundguy"]Does anyone know if those meter bezels are available seperately in the world or am I stuck buying an entire new meter assembly? [/quote] THey are... but what version 1176 is it?

THe black-face ones with Modutec meter illuminated from the top used one type of Bezel, the rear-illuminated transluscent scale meter on the silver faced version used a different type, and the blue-stripe early ones used another type altogether...

I too need a bexel and I know where to get them.. they're cheaper if you need 5 or more though...

Keith

the unit is missing the meter completely, but I have a bunch of meters here... I was hoping to put a modutec in there since I have some... Top illumination.

dave

Check your PMs...

Hello,
Here is what I did on my 1176






Fly

fly-

that looks great! Thats exactly what I need to do. Is that running off of AC or DC voltage? Could you describe how that is wired? Its easy enough to see but cant tell which is the anode and cathode...

thanks!

dave

Thankssoundguy,

It's 4 white leds and 2 res. (470R .5w) connected as this :
>> 470R+led +led +led+led+470R <<
and running off of DC from the "VU LAMP" connector just near the 7824 reg.( PCB top right side).

Fly

hmm

isnt ther about 40V ac at the point?

thats like 40ma running through those led's


I'd up the resistance... maybe two 640's get more life out of the led's

I know on the purple boards its ac not dc at those points

Hi SCENARIA,

No, it's DC comming from rectifier and running ±35v on my 1176,
White LEDS are running with 3v5 and 20mA, so...

friendly
Fly

re: bezels, i tried a sifam AL29 bezel and it fits the 1176 style modutec i have. if you look up sifam on farnell you can find the bezels by themselves, and newark lists a few of them as special order, around $5, so i bet they could get one for you.

ed