Show some love for the newbie

951guitarist · September 21, 2009, 12:07:37 PM

I just signed up today and have been reviewing the site. I am pleased to have found it. I have not done anything in electronics for years and have, probably the simplist of questions (remember the subject "show some love for the newbie")

I have an old MXR Microamp that works great but has no LED indicator, how can I install a simple on/off led.

Thanks

liquids · September 21, 2009, 12:30:49 PM

Welcome!

It's a fine project, and while 'basic,' it's very gratifying when you actually get it working. I had a similar project as my first endeavor - changing out the stomp switch wiring and eventually re-housing my MXR Phase 45 with an LED.

Anyhow, here is a start while others can chime in.

You want a 3PDT stomp switch. This should help you wire it.

http://www.beavisaudio.com/techpages/StompboxWiring/

Note that you might want to simplify by buying an LED assembly that comes pre-wired in your color of choice, and has a built-in resistor, especially if you are using an adaptor, but it's not necessary.

Also, some things to think of - make sure you document with photos and or paper, what wires color go from where to where, before you do any work. This will prove useful in case you get lost or one comes disconnected, since that is not something that is common knowledge.

You'll need to do some drilling, and also need to make sure you can fit the switch in the box. I'd say you probably cant fit it...so you may want to consider buying a nice pre-drilled 125B from pedal parts plus, unless you are comfy drilling yourself, are sure you can fit the new switch in the box and/or don't want to ruin the original box by drilling it.

It's more physical than electronic, when it comes down to it, but it's a good thing to learn on. Also, do consider preserving your old pedal and just building a replacement from scratch. I bought mine hacked up so I didn't mind modding mine, so it depends on your preferences. That being said, building one from scratch wouldn't be that much harder, the sale of the vintage box might fund more than just the parts for the home-built version, you'd get lots of help here, and it might be fun!

Good luck!

951guitarist · September 21, 2009, 12:55:11 PM

Thanks, I'll give it shot.

951guitarist · September 27, 2009, 08:04:26 PM

Hey Liquids, Feeling really dumb at this point. Went to the suggested link and order and rec'd all the goodies. The LED holder two piece with washer and nut. how does the led and the base stay together. Is it a press fit? How much pressure or am I missing it all together. Could use more rookie advice.

Thanks

liquids · September 27, 2009, 08:17:44 PM

I hear you. LEDs and I are enemies in this regard.

Whered you get the LED holder? Or did you get an LED assembly that comes pre-wired from mouser, etc?

Either way, if not pre-assemled, most of them have some odd device to hold a loose LED into the hardware..I've yet to find one I feel comfortable with how it fits. The pre-assembled ones keep the LED in there very nicely, and have a little 'lip' on the plastic holder so that if you drill the right size hole, it fits nice and snuff and wont push through the box.

With the self-assemble ones...you might want to use some glue, a glue gun...I hate how that turns out so, now that I recall, I have a pile of them I've ordered and thrown at the wall....

951guitarist · September 27, 2009, 08:42:40 PM

Well , I was going to send you a photo but that's another protocol issue. anyhow I purchased from pedalpartplus and it was individual parts. The LED only goes in so far and the little plug that fits into the rear of the holder goes in maybe a 1/16 if that and feels like it should almost press in. I just don't want to put any real pressure on it.

You suggestion then is a hot glue gun (that glue's not conductive is it).

Thanks

951guitarist · September 30, 2009, 05:13:55 PM

O.k. Not sure what I did or didn't dO. I bought the necessary parts from pedalpartsplus, the recommended switch and a 1/4wt 2.2K res. and a blue T1-3/4 5000mcd 5mm LED. The problem is that I wasted the LED, the voltage on the output side of the resistor is the same as the input voltage (8.78 vdc).

What did I do wrong? It's been 30 years since the last time I did anything like this. This sounded like a simple project.

aziltz · September 30, 2009, 07:02:51 PM

Quote from: 951guitarist on September 30, 2009, 05:13:55 PM
O.k. Not sure what I did or didn't dO. I bought the necessary parts from pedalpartsplus, the recommended switch and a 1/4wt 2.2K res. and a blue T1-3/4 5000mcd 5mm LED. The problem is that I wasted the LED, the voltage on the output side of the resistor is the same as the input voltage (8.78 vdc).

What did I do wrong? It's been 30 years since the last time I did anything like this. This sounded like a simple project.

Is the resister between the LED and 9v?

Perhaps the LED is backwards. If it was backwards, it wouldn't light, and you would get the same voltage reading on both sides of the resister because its not conducting any current.

951guitarist · September 30, 2009, 07:21:33 PM

I understood this to be the order, 9v-2.2K ohm res-anode side of LED. Problem is that I am still reading 8.8-8.9 Volts after the resistor and this is blowing the LED.
I am trying my best to understand this, like I said I am really having to knock the rust off the brain to remember all the formulas. As I was able to research. a blue High intensity LED sheds 3.3 to 4.5 volts, I should be anywhere from 270 - 300 ohms resistance, right? I am only asking so please no one get offended how did the 2.2K resistor come into play or did I just make and assumption based on the generic schematic I was given?

Just trying to understand before I spend some more money (I know we're talking a buck or two here).

Thanks

aziltz · September 30, 2009, 07:30:50 PM

2k2 is a "normal" value, so I'm not sure what's causing it to blow. Obviously its getting too much current. You can always try a higher value. Try 10k and work your way down.

Is the LED actually Lighting up and Blowing Out? or is it just not lighting?

If its not lighting, then I still think it could be backwards. That would cause there to be no drop across the resister. Either way, you can normal take an LED straight to a battery for a few seconds without blowing it to check the polarity. I'm speaking about the LEDs from PPP or effects connection and small bear.

951guitarist · September 30, 2009, 07:41:01 PM

When the LED is hit with 9v it lights briefly and then out. KAPUT! It is definetly too many volts. If I test them with a straight 3v, no resistor they are fine. I tested the resitor and it reads 2.1 (could be the variance in my cheap tester as to why it dosen't read 2.2) why then do I get 8.8-8.9 volts on the out side of the resistor? I feel like I am not unnderstanding something here.

aziltz · September 30, 2009, 07:53:58 PM

Do you mean 2.1/2.2v when you are using 3v as your power? When you test at 9v, is it connected to the rest of the circuit or just a battery or PS?

There's definitely too much current going through the LED at 9v. I would try a higher resister and adjust, you might have some lower current LEDs, I don't know

951guitarist · September 30, 2009, 09:01:53 PM

We have all sorted out now. Thanks guys. I had the switch orientation wrong and the wrong wiring config on the LED.

NEWBIE

It'll all come hopefully.

Thanks again.

aziltz · September 30, 2009, 10:58:06 PM

no worries. i hope i was helpful.

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