Burnt Resistor
My brother has an old LED sign that he has had for years. It advertises his business and phone number as the LED letters scroll by. It finally stopped working after years of non-stop working, so he asked me to take a look at it. Since I am the know-it-all fix-all Jack of All Trades, I decided to give it a shot.
1 if 3 internal power supplies
The LED sign came with 3 internal Power supplies that when plugged in, convert the 110 VAC into 5 volts each to power 1/3 section of the LED sign each. Since the first one of these power supplies also powers up the "brain" of the LED sign, without it the whole sign is dead. When I checked the power supplies, it was the first one that was not working so when I took a working one and placed it as the Power Supply #1, then 2/3 of the Sign now lit up, and the letters began to scroll.
Upon closer inspection of what was Power Supply #1 showed that a resistor had burned out. The rest of the unit looks in working order. So now the question is what size is this resistor. The burned one is no use because the heat discolored the colored bands around the body of the resistor which help indicate the type of resistor it is.
So the image above shows a good resistor with the colored bands photographed from one of the good working power supplies. Since I am no expert, I believe this resistor to be a 10K Ohm 5% tolerance 1/2 watt Metal film resistor. The resistor is on the 110 VAC power in side. This is the one that needs to be replaced on the bad power transformer.
Of course I will not hold anyone liable for any help they attempt to give. Ultimately the decision will be mine on which resistor I try, but some expert opinion or know how would be nice. I have looked at the wiki site that shows the different sizes and watts of the resistors, and I believe that the color bands are Brown, Black, Orange, and Gold. I am least confident on the Gold color, and then the orange. I am very confident in the Brown and black band color assessment.
Based on this, I thus believe it is a 10k Ohm 5% 1/2 watt metal film resistor. I will wait a few days before ordering the resistor to see if there are any electrical engineers or electronics experts here on Steemit that could at least offer a little guidance. Or if any of you know someone with the smarts to help with this, please let them know about my little dilemma.
The manufacturer of the LED sign no longer makes or sells parts for this unit. Should this fail to fix the power supply, I do have a work around in mind.
Thank you all, @streetstyle
From 1990, I remember this ... Bad Boys Rant Over Young Girls But Violet Gives Willingly. Black=0, Brown=1, Red=2, Orange=3, Yellow=4, Green=5, Blue=6, Violet=7, Grey=8, White=9
So, I agree 10*10^3 = 10k with a 5% tolerance.
But ... I question whether the resistor is the cause or the symptom. From your picture, I would replace R3, R2 and Q3 with a suspicion that it was actually Q3 that went.
Q3's job is to act like a gas pedal. By putting a little pressure on the gas pedal, you can control a lot of horsepower. Similarily, by putting a small current on the base of that transistor, you control a lot of current on the emitter/collector.
The discoloring looks like a buried plane heated up enough to discolor the substrate. So, the weakest link may also have been in the circuit board. If you are comfortable with a soldering iron, I'd recommend pulling R2 and R3 out and measuring them with an ohmmeter to see if they are actually blown. (Maybe pulling out the good R2/3 from another power supply and compare) Is the bottom side of the circuit board discolored as well?
If you look at the face of Q3, you should be able to read the part number and can get a replacement from Digikey or similar.
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Thanks so much for such amazing info... I love STEEM. Thanks again @gikitiki
So what do you think, here is the backside. Still worth trying to save this board? If so, should I just replace R3, or also R2 and Q3?
Would Q3 show any external signs, the picture doesn't do it justice... cause it looks fine. I can take a better pic if you'd like.
Your wisdom is appreciated.
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It looks to me that the pins or Q3, R2 and R3 all got hotter than the melting point. I'd start by removing R2 and R3, then testing their resistance. If you have to buy replacements, I'd definitely buy 2-3 of each (they are cheap) and include Q3. It will likely cost more in shipping than the parts themselves.
Are there any other pins on the backside that don't have the nice smooth look? i.e. that might have also melted recently? Possibly a part that has a heatsink on it?
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ps, you got a new follower, so when you make your next post I can support.
I like your style btw, I think you might be a multipotentialite @gikitiki
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Cool.
I just noticed that you were one of the driving forces for #spud. I'm proud to say that I did my little part. :-)
And yes, I do consider myself a bit of a multipotentialite. I'd just never heard of the term. Tonight ... there will be Ted Talks!!
Thanks for the label. :-P
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Yeah, It was new to me too until someone on Steem posted about it, I saw the Ted talk and then things made more sense. Cool stuff. Enjoy and again, thanks for the wisdom and advice.
As for the board, I don't really see anything else that could be suspect but then again I am untrained so not really 100% sure what I am looking for and I am getting older so my sight isn't what it used to, although these new cameras are amazing and help with that part. I included a pic of the back to see if you see anything that I might have missed.
And as for SPUD, yeah, I am a long time long term believer in STEEM, and this here reinforces that belief. Thank you again.
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The rest looks good. I'd try swapping the 3 components and go from there.
https://www.digikey.com/products/en
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Wow!
This has taken me back to my childhood in the 1970's when I used to build electronic games.
Shared on twitter to see if anyone can help.
Stephen
https://twitter.com/StephenPKendal/status/1125824772766674945
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Thanks so much for this @stephenkendal..... gotta love steem.
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Mucho cuidado al trabajar esos aparato amigo,la corriente muy peligrosa,saludos y muchas gracias,hoy he estado un poco mal con irritacion de garganta y un poco de calentamiento de cuerpo ,no fiebre pero si me he sentido incomoda al sentir ardor para tragar,en un rato voy en busca de algun medicamento si es que hallo jaja una odisea .feliz noche
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Gracias Petra, espero que este mejorando de salud. Y si, miedo le tengo a la electricidad, pero estos no son voltages muy altos, aun si tengo much cuidado. Gracias, saludos y buen dia.
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Buenas tardes amigo @streetstyle deseo que se encuentre bien al igual que su familia amigo , la placa madre donde están esas recistencias hubo mucho recalentamiento y quemó un poco la placa al proceder a cambiar la recistencias tenga mucho cuidado cuando valla a sacar la otra ya que la zona donde tiene que retirar el estaño para colocar la otra está muy débil por el recalentamiento. Que tenga una feliz tarde
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Gracias @edgargonzalez Pues haber como me va con esta cosa. Ciao y buen dia y saludos. Cuidese.
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Excellent review @streetstyle and I'm certainly not an engineer, but in my youth I was fond of radio. If I have such problems, then I go to an electronics workshop and buy a used resistor, with a similar electronics model from a master, but on condition that it is available.
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Not an expert in this but this site may really help you out
http://resistor.cherryjourney.pt/
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Thanks @blazing I appreciate any help I can get, but so far @gikitiki has been awesome wealth of knowledge.
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Espero de verdad que puedas conseguir quien te ayude a resolver ese problema Electrónico amigo @streetstyle. Saludos y que tengas una Feliz noche
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Over to electronic experts! Lol 😂
Thanks for sharing @streetstyle.
Posted using Partiko iOS
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Thank you so much for participating in the Partiko Delegation Plan Round 1! We really appreciate your support! As part of the delegation benefits, we just gave you a 3.00% upvote! Together, let’s change the world!
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