Silly question on 1176 light..

Im near to the end of my first 1176.
But i've got a doubt..maybe silly..
I buyed from RS the Sifam VU with their illumination kit, i just discovered that are 12V (0,1A seem), what is the volts from the pcb? 48v or less?
what kind of resistor ohm/watt (in serial i suppose) i have to use in this case?
Regards,
Corrado

Best to use the AC voltage directly off the secondary on the power transformer.

Measure the AC voltage here with the unit running

calculate how much voltage drop you need to get to the 12V

calculate dropping resistor from the drop voltage and the light currrent

R=U/I - resistance in Ohms = Voltagedrop (in volts) / current (in Amps)

Use a slightly larger resistor than calculated - lamp voltage a bit on the low side prolonges lamp life considerably.

and, btw - make sure that you have the needed extra lamp current available from the power transformer..

Jakob E.

here's an even sillier question..

do you think can we use a simple christmas light attached to the meter for illumination?

The christmas light thing would probably work, but I'd question how long its going to last being turned on for long periods of time for a few years.

[quote author="bradb"]do you think can we use a simple christmas light attached to the meter for illumination?[/quote]

Just take care it?s not a flashing light? :green:

[quote author="gyraf"]Best to use the AC voltage directly off the secondary on the power transformer.

Measure the AC voltage here with the unit running
[/quote]

Where should the leads of the multimeter be placed? I'm set to AC on my multimeter but I'm not getting the reading I expect.

Across the filtered but unregulated DC would work just fine, that's where the original 1176 got its DC. You also dont want to have AC wires just run close to audio circuits.
Just make sure the lamps are the correct voltage, 2- 28 volt lamps in series should be OK, The 1819 lamps are 28volts if my memory is correct.
You could also use those axial lead type lamps, mounting may be a problem.

With the Sifam AL19s (dual 1176) you can wire two 12v bulbs in series and run them from the 30v DC powering the board. You don't need much light. You'll want to drop at least another 10v to make them last so a resistor in series with that circuit would be a good idea. Start with 100r 2w and move down from there.

I changed all my lights on my dual 1176 to LEDs (power indicator, vu1 and vu2). LEDs are easily soldered between the tabs on sifam meters. I used a 1k 2w dropping resistor in series with 30v dc coming from psu.

$.02

Kenrinc-

I used a little vintage Calrad edgewise meter on mine, a string of four little red LEDs with a 1k2 1W resistor in series.

To illustrate the bits of Ohm's law that Jakob gave....

24VAC x 1.414 = 33.9DC (peak).

In reality closer to 36VDC, so 36 minus 24 to get 12VDC for the LEDs.

24V/.020A (that's 20milliAmps) gives 1200 ohm resistor.

EDIT: I just noticed that Purusha had a nice picture of the LED for meter illumination technique:

http://www.groupdiy.com/index.php?topic=248976#248976

Hey skipwave!

Sorry if his is a little OT , but that calrad edgewise meter you are using ...is it LINEAR scale? If so , how are you going about using it in the 1176 which asks for VU ? (..or VU-ish anyway (AL series etc...)):?:

I ask because I just picked up a lovely big old Taylor edge meter (early 60's I think) and that is a linear scale , but I was wondering about using it in an 1176 which I'm putting into a 1u case.

I used a couple of old hifi dc meters in my first 1176 , with added rect/capacitor , and found that to be adequate for my needs , but those meters already had a 'vu' scale printed on them...this linear one doesn't.

Just wondering if u had this problem too...and how you got around it....maybe your meter's a true vu anyway???

Many thanks , and sorry for jumpin in on lamp discussion ..but i'll definitely second what skipwave said about 'led string' ...the "ultra bright" ones with not too narrow a projection angle x 3 worked for me , lighing up those big JVC meters I used!

Cheers

nEon.