Panel illuminated pushbuttons - Page 1
Forum section: electronics / projects

author: Zeyneb
author_rank: Regular Contributor
timestamp: September 01, 2018, 12:09:02 pm
content: Hi thereI'm having an audio amplifier with the EAO 61-1200.0 illuminated pushbutton switch for the main on-off function. It's the flush 30x24 mm design. The 30x24 spec are the outer dimensions of the black bezel that surrounds the lamp/led lens.Now the filament lamp has died. But this thing require some special tools for servicing. The lens has to be removed with some tool: 61-9730.0 that cost €5.84 at Farnell. I was bored of the red lens so a new green one is €2.91. For durability I prefer to go for a LED instead of a filament lamp. EAO specifies the LED socket to be "T1 3/4 MG", that is pretty standard is it? So, I don't necessarily need go for a EAO branded one?Do you always need to buy a T1 3/4 MG led as a whole unit? It's never possible to manually install a T-1 3/4 leaded LED into a generic MG socket? Regarding the electrical stuff, I understand how to use standard T-1 3/4 leaded LEDs. But EAO specifies an operating voltages like 12 VAC/DC or 24 VAC/DC as well as a operating current. I don't really understand this. Is the T1 3/4 MG the LED with a reverse zener diode in series? Or what else is it electrically?In general, EAO is good stuff is it? While not being too expensive. Or should I consider replacing the whole pushbutton unit with something that is easier serviceable?Regards,Zeyneb

author: t1d
author_rank: Super Contributor
timestamp: September 02, 2018, 03:35:48 am
content: You have given this good consideration. Great. However, you are not likely, to get specific replies, I think, and I don't have one, either.- As for the tool, it looks like a fork that pushes back the clips that are holding the switch cover. You can probably make this, yourself. Is a paperclip too thick?- As for replacing parts, or the whole switch, you have the information, to make the consideration... Availability of parts, their cost, your time and effort, etc.

author: TimNJ
author_rank: Super Contributor
timestamp: September 02, 2018, 03:50:55 am
content: If you go to their website, you'll see that these LED replacement indicators are meant to be used to replace 12V filament lamps (which can run on either 12VAC or 12VDC). LEDs, however, don't do so well with blocking reverse voltage, so they include a single diode (half-wave rectifier) in the package. Though they don't explicitly say it, they provide a current spec of 3/6mA...implying that it also has a ~2K series resistor to provide current limiting.So in your case, you can'tjustuse a regular T-1 3/4 LED. You need to provide a rectifier diode (if the lamp gets its power from an AC source), and definitely a current limiting resistor to prevent the LED from burning up.

author: SeanB
author_rank: Super Contributor
timestamp: September 02, 2018, 08:05:28 am
content: Done a few LED conversions, you take the old lamp, gently crush the shell with some pliers to break the glass out, and unsolder the pin from the bottom and the little bit of lead wire from the top. Then take a 3mm LED of the right colour ( easier these days as you get insanely bright LED's in a water clear package) and bend the one lead out 180 degrees ( support the lead by the plastic body so as not to crack the internal bonds, using some needle nose pliers) so as to be the body side, then place a short length of plastic sleeving over the other ( serves more as depth locator than insulator) and push this lead through the hole in the lamp case where the old lead was. Then solder it to the terminal button, and solder the outer lead to the case after bending over . Then put the new unit back in, and arrange the resistor and bridge rectifier needed on the rear of the switch body. If the light is to bright in the centre gently sand the top of the LED with some 400 grit waterpaper to make it more diffused.Those switches have a tool to open them, but generally 2 small bladed jewellers screwdrivers will pop the cover when used in the right place( the short side of the switch where the catches are) and a small piece of flexible rubber tubing ( 5mm diameter) placed over the bulb will pull it out.

author: Zeyneb
author_rank: Regular Contributor
timestamp: September 03, 2018, 04:07:58 pm
content: Thanks for the suggestions. I decided to continue with this EAO assembly and buy some parts for it at Digikey.At Digikey they also provide a T1 3/4 MG LED from another manufacturer, VCC.part VC1512125UG3-NDthat one is a bit cheaper than the EAO one. But still expensive in my perspective.Regards, Zeyneb