SSlmixed.com Forum
Tech discussion => 4K,6K,8K Series => Topic started by: marcmozart on February 19, 2013, 10:02:10 PM
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I'm trying to get my head around this whole LED thing. I'm not at all knowledgable in electronics. I do understand that the VU meter illumination bulbs had 48V and the CUT/SOLO-bulbs 36V.
I also understand that resistors must be used to limit the current as most LEDs are rated at 20 mA at 3.2 volts.
Can anybody explain and perhaps give examples for what LEDs to buy and how to put this all together?
I found this "LED array wizard", but when feeding it with the typical values, it kept telling me "the wizard thinks the power dissipated in your resistors is a concern".
http://led.linear1.org/led.wiz
Cheers,
Marc
www.mozartandfriends.com
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My board has been done.
I'll try to get a pic up of the LED later today. It's very basic. An LED and 2 resistors.
Stef.
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Cool, thanks!
Meanwhile somebody told me that for the CUT / SOLO / etc. there is an direct LED replacement, but - fairly expensive at around 2-3 Euros each. Apparently these are SUPER-bright.
JKL Components
Z-T55-NW (white)
Z-T55-G (green)
Z-T55-R (red)
I'm sure there's a DIY-solution involving a component LED and a resistor that's slightly cheaper.
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Really the DIY approach is a really cool way to go :))
You need to recycle old blown bulbs, and use the metallic bits as a basis for the new assembly.
A current limiting resistor on the positive side, a Superbrite LED and a coloured bulb condom.
Did this for a Bus compressor IN switch bulb 8 years ago.. and it's still working great!!!
I know Mattia has done this also, again with a single resistor.
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Here's a pic.
(http://i1263.photobucket.com/albums/ii622/StefNowak/IMG_0730_zps91fae9d0.jpg)
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Awesome, thanks! What types of LEDs and resistors are you using?
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Unfortunately I can't answer any tech questions as the board had been modded already when I bought it.
Sorry.
Stef.
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I'm going to do some bench testing to workout the values that look closest to the real bulb with it's coloured condom.
I have some of those 36v LED alternatives, I gotta say they don't look good :(
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Yeah I have a few off the shelf LED replacements and their colours are just wrong.
I'm going to email the tech that did the mod, hoping he might have some info I can share.
Stef.
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I have done some in a 4K I am working on.
basically you have to experiment. I think I have bought 3/4 different types from FARNELL in UK with different emission angle and tried to see what it looked like.
the wider the angle the better.
as far as resistors I don't see the point in putting 2 rather than being easier to mount the LED on the metal frame.
as far as resistors is concerned here is the maths. please someone correct me:
LED rated at 1.2V rails are 18V
36-1.2 = 24.8 V of drop that needs to be achieved.
current 20mA (if you think you'll use less current you are wrong as the original bulbs also take 20mA) so resistance needed is = 24.8 / 0.02 = 1.240 ohm (1.5K works fine)
power dissipation of resistor: P=VxI = 24.8 x 0.02 = 0.496 W so a 1/2W resistor (0.6W it's pretty standard now days) will do it just fine.
in case you wish to use 2 resistors :
R= 750 ohm per side power stays the same.
I have step by step photos of mine somewhere, I see if I can find them, I am getting on a plane to work on a duality shortly so not sure if I will manage...
EDIT= lost it somewhere.... sorry chaps.
Mattia.
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Hi all,
I am making a bunch of LED bulbs for replace the original bulbs of the switches.
I am using these componets for making them
- LED reference: OSCH4L5111A
https://www.tme.eu/es/details/osch4l5111a/diodos-led-tht-5mm/optosupply/
- Resistor reference: MOF1WS
https://www.tme.eu/es/details/mof1ws-1k8/resistencias-metalizadas-tht-1w/sr-passives/
I use the original rubber caps for coloring and also plastidip liquid rubber (https://www.plasti-dip.es/vinilo-liquido/plastidip-goma-liquida-429ml/)
The new LED bulbs work fine but I have 2 channel strips where I replace the led bulb into the SOLO switch and the light is on, althought the SOLO is pushed or not. I mean, the light is on all the time. I do not know why is happening this on those two channels.
Any idea?
Thanks in advance.
I hope you all are healthy and safe in these times.
Oihan
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The solo lamp is driven directly off the solo switch, unlike others via a FET.
Check you have +18/-18v coming to the switch. Not much can go wrong here.
Page 1-14 of the service manual.
Anthony,
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Thanks for answering Anthony.
The question is that those channels work fine with original bulbs. When SOLO is on, the light is on and when SOLO is out, the light is off with the original bulb. I had check page 1-14 before I wrote here and I was thoughting if I was missing something, because it looks pretty simple. But I was confused... If SOLO switch is open... how can do light a LED bulb? And why it does not the original bulb?
Could be something relationed with the logic card? The diode D3 or D2 or something like that...
I will check it and write back soon.
Regards.
Oihan
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Also check D7 on the 651 motherboard. If that's shorted or leaking it could also cause the LED to stay on.
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Hi
D7 diode of the 651 motherboard seems it is ok in both channel strips. I have swapped a tested logic card om both channels and the issue is still there. Any other idea?
Thanks in advance.
Regards.
Oihan
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Hi,
I have been testing and working on one of those channels. My electronic skills are limited, so I am stuck right now. I tried to find the problem in one of those channels, because it seems is a similar issue.
I have replaced the diode D7 of the motherboard and diodes D2 and D3 of the logic card (82293). I also have replaced the switch, just in case. The issue still it was there, so I took some readings in differen points. I supose that, on pin 40 of the VCA card (82E13), I should have the same value (around -18v) in both sides of the bulb contact. So the difference between those 2 poles, should be around 0v. I am measuring a difference of 16,5v (when SOLO is not pushed), that is the reason why the LED still light when the SOLO is nou pushed. I do not know where is the issue. I swapp the VCA card (3 different cards) and I get the same value around R6 resistor (one side it is correct -17,54v and the other side is giving -1,42v).
I have attached some screenshots with the readings.
I would appreciate if someone could give me any idea!
Thanks in advance.
Best regards.
Oihan
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Oddly enough, the same thing has just appeared on one of my channels (solo LED staying slightly lit).
It happened after I changed out to a different logic card, which was untested.
So I suggest that the issue is on the logic card, but I will swap it back to the old one today.
The 212 drive transistors fail regularly on those cards.
Anthony.
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Thanks for answering Anthony.
I have tested also different logic cards, before replacing the diodes. But I will try doing some more tests.
I will write back soon.
Best regards.
Oihan
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I changed back the 82E12 logic card to a known good one, and the Solo light issue is resolved.
Will troubleshoot that card later.
Anthony
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I have been changing 82E12 logic cards, working cards from other channel strips, but the issue is still there.
I will leave this on standby, i will continue fixing other small issues I have in the console.
Any new idea it would be welcome.
Best regards.
Oihan
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Hi all,
Finally I found the issue!! Yesterday I was checking all the pdf files I have in my laptop and I found the old schematics of VCA Solo Cut switches. There are D6 and D5 diodes, witch are not presented in the generic manual. In one of the channel, the diode D5 was asembled inverted!! From stock!! and in the other channel, the D5 was broken. So, if someone has a similar issue in the future, check the D7 and D5 for the Solo switch, and D6 for the Cut switch.
Now both Solo switches work fine with LED bulbs.
Thanks for making me think!!
Best regards.
Oihan
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anyone has got any leads for the VU bulbs but with LEDs?
Matt