4K LED Replacement VU meter and bulbs in CUT/SOLO etc.

[marcmozart]

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

[StefanNowak]

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.

[marcmozart]

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.

[sintech]

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.

[StefanNowak]

Here's a pic.

[marcmozart]

Awesome, thanks! What types of LEDs and resistors are you using?

[StefanNowak]

Unfortunately I can't answer any tech questions as the board had been modded already when I bought it.

Sorry.

Stef.

[sintech]

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

[StefanNowak]

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.

[Matt Sartori]

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.

[oyanliz]

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

[horizonsound]

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,

[oyanliz]

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

[Chris Simon]

Also check D7 on the 651 motherboard. If that's shorted or leaking it could also cause the LED to stay on.

[oyanliz]

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