blackeyeliner
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Here's how it looks:
Circuit modification: powering a VU meter board
- Thread starter blackeyeliner
- Start date
A terminal strip or a piece of proto board can make that more durable/safe. A 6V winding into a diode bridge will give 4-7V, depending on load and diodes.
-PB
-PB
blackeyeliner
New member
So I rebuilt the doubler with a new capacitor. It is weird but it's working perfectly when the sound inputs are not connected to the board, the lights go on, doubler produces it's 13.5V DC, but if I connect the sound input, lights on the board (meters illumination) go off and it starts humming into the sound circuit.Caucasian Blackplate said:
I obviously measured the current flowing through the doubler and with the sound input connected, it's 2+ amperes, while without sound inputs connected, it's normal 0.08A. Is there something I am terribly missing?
blackeyeliner said:
Yes, undoubtedly something is very wrong there, but it's hard to know without knowing a lot about the VU board setup.
-PB
blackeyeliner
New member
So you think there's nothing I can do on my own at this point? I guess the board design will be hard to get somewhere. It's pretty simple, but I don't understand how connecting audio can make it draw 2+ amperes, really. At the same time, any external power source makes it run perfectly well.Caucasian Blackplate said:
blackeyeliner
New member
I just thought that probably an easier way would be to use the fact that the board can be powered with AC (it has a diode bridge on it and a stabilizer afterwards) and just find a very small low power transformer, install it inside the case and power in parallel from the switch...
That's probably a better idea. 12V transformers are very easy to find.
-PB
-PB
blackeyeliner
New member
So it appeared that 12V is not enough for this board to function. It was technically working, but it has a 12V regulator after the diode bridge, that needs 18-19 volts DC to output 12V stabilized. I found a small 24V transformer, put it on a small board, drilled a couple of holes in the casing and here it is, working like a charm. The only problem is that the transformer gets pretty hot.Caucasian Blackplate said:
blackeyeliner
New member
So to close this up, I ended up installing a radiator on top of the transformer, replaced the transformer with a lower voltage one so it generates less heat. It's still hot, but the rest of the amplifier is the same temperature.
So I guess this is it, it seems to work, spend the day on, like 8 or 10 hours already.
So I guess this is it, it seems to work, spend the day on, like 8 or 10 hours already.
mcandmar
New member
What is the VU board you are using? Most voltage regulators need higher voltage then their output, for example for 7800 series or LM317's they drop out when the source supply is less than 2v above its output voltage so +4v is usually a good target to aim for. Going too high, like feeding a 12v regulator 24v will cause it to run very hot as it has to dissipate the extra voltage.
A hot transformer could indicate the load is higher than the transformers current rating. Generally those small PCB transformers do run hot so its usually a good idea to fit one rated for more current than it needs to supply, assuming you have the physical space.
A hot transformer could indicate the load is higher than the transformers current rating. Generally those small PCB transformers do run hot so its usually a good idea to fit one rated for more current than it needs to supply, assuming you have the physical space.
blackeyeliner
New member
They have changed the layout of the board since I bought mine, but it's something like this: http://www.ebay.com/itm/2pcs-Panel-VU-Meter-Warm-Back-Light-Audio-Level-Amp-One-driver-board-/121468037573?pt=LH_DefaultDomain_0&hash=item1c480f29c5mcandmar said:
You are right, they are using 7812 regulator on this board, and I measured, it does not run very hot in my application. It gets 22V DC input from the rectifier bridge and then regulates to 12.0V. Right now I have installed a 18V AC transformer that is rated for 0.16A, whereas the board consumes 0.8, so fine here.
I then run the transformer outside of the case for several hours to understand if it's overloaded or something - it doesn't get hot at all, like 30-40 degrees maybe 50 tops. Inside the case, hanging upside down, it does get pretty hot, I presume because the overall temperature inside a Crack case is high, everything dissipates a lot of heat. It's been working for a week for me, sometimes 8-10 hours non-stop, with no problem so far.
