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Discussion Starter #1 (Edited)
When I put the dash back together with my new cluster repro PC (and the dash pad back in - which will now come back out arrrrrgggh), one of the dash backlights was out, the bulbs are all good, just seemed to have some bad contact with the sockets with the new PC for some reason. I missed the one back light being out, they are kind of dim (and of course it is in the middle upper, under the high beam indicator). When I looked at the dash in a dimly lit garage (how romantic! :buck: ), I found it and reconfirmed how dim the backlighting is, even at highest setting.

So, yesterday it occurred to me, why not upgrade at least the backlighting bulbs to LED? So I went looking. I like (and ordered 10 of) these:



I highly doubt they are German LED's (AGT = Advanced German Technology, probably some weak Chinese attempt at marketing?) but figured they had some slim chance of being better than the Chinese crap you can buy from a zillion places on feebay.

Anyway, I think I will have to/want to remove the blue diffusers from the cluster housing (because these LED replacements are about 1.125" in length, longer than the 194 bulbs and will hit the diffusers). That and I read somewhere that the idea of the diffusers originally was yellow light, blue diffuser, greenish light? We'll go for straight white (ordered white LED's) and see how things look.

Think I made a good choice of bulb type/configuration (amongst the many), 4 large chips around the sides and one on the end. Should (I hope) throw a lot of light around as the originals do. I looked at the 10 chip and 20 chip configurations of this type too but went with these figuring less cheap Chinese chips to burn out? I know some people have tried other bulb configuration types and the directionality of those types was an issue.

So what has peoples experience been?

Oh, and do these LED bulbs dim okay with our headlamp switch dimmer rheostats (or at least dim somewhat, I figure they might just turn off below a certain voltage)?

Thanks,

Bob
 

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Discussion Starter #3
Hey, thanks Carlton. I had looked at that site, but not the notes, good stuff. They say the LED bulbs will dim, others have said they won't. Will be interesting to see how it goes. Hopefully my choice of LED's with 5 chips emitting on the four sides and off the end will approximate the omnidirectionality of a standard incandescent bulb. I'l be sure to let you all know how it goes.
 

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Discussion Starter #4 (Edited)
Hey, thanks Carlton. I had looked at that site, but not the notes, good stuff. They say the LED bulbs will dim, others have said they won't. Will be interesting to see how it goes. Hopefully my choice of LED's with 5 chips emitting on the four sides and off the end will approximate the omnidirectionality of a standard incandescent bulb. I'l be sure to let you all know how it goes.
1/23

Got my package and tried them out. Plenty of light (too much?) and they dim very nicely cranking down the voltage on the power supply I was using. As for why an incandescent lamp in parallel would aid in dimming, I think I understand why. The incandescent draws considerably more and creates the needed voltage drop (by virtue of its current draw) across the dimmer rheostat. If the lamp were not present, the LED's perhaps do not draw enough and so the rheostat resistance is not enough to create the needed drop in voltage at the current the LED's draw. Will report back with results with the little buggers installed into the cluster.

1/24 am

I measured the current draw of a 194 bulb and one of my 5 chip LED 194 replacements this morning before I left for work. The 194 draws about 260 mA and the 194 LED replacement 60 mA. So the LED draws less than 1/4 of the 194. Hoping the dim function will work without having to add a dummy incandescent as Mike mentioned, but will keep that in my quill should it be needed.

1/24 pm

Got the LED dash backlighting installed tonight, looks real good, white like original (with diffusers removed) and bright. As some said, the dimming range is minimal, but don't think I really need more anyway, I LIKE being able to see my gauges and what they say! There are two clock lamps, the AC/heater control light and prehaps a console light (didn't look) as well so perhaps those being incandescent is helping with providing some dimming capability. I am very happy with these LED bulbs for $1.50 each (in a quantity of 10), the 69/70 XR7 cluster uses 5 for backlighting.

Today

So yesterday when I was ordering a few parts for enhancing the ELFI design's functionality, I thought why not order a "ballast" power resistor to draw the missing current left from using 5 LED lamps where 5 incandescent used to go in the dash (to make dimming more like it is with stock 194 bulbs). My LED's draw 60 mA each, so that's 300 mA total, while the stock 194's draw about 250 mA each, so about 950 mA less current is drawn. 12V/.95A = 13.47 ohms. I ordered a 50W (was cheaper than the 25W), 12 ohm power resistor, overkill, but will keep cool that way, only about 13.7W will be dissipated in the resistor. Result should be just-about-like-stock dimming on the headlight switch rheostat. Will let you all know how the experiment turns out.
 

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Bob, good stuff, I used LED's in the tail-lights of my 67, which I have 8 (I added 2 extra when I eliminated the gas fill lid) I had to leave two regular bulbs in the circuit for them to flash correctly. They are much brighter, and flash faster than before, the only thing now is that my dash indicators don't flash, they just stay on.(they are also LED's)
 
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