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About RDL2004

  • Birthday 08/25/1956

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  1. Maybe this will be of help: http://sound.westhost.com/project55.htm Analog meters have not totally disappeared, for example: http://www.mcintoshlabs.com/mcprod/shopdisplayproducts.asp?hid=1&id=14&cat=Power+Amplifiers&prodid=1028&product=MC602
  2. Remember that LEDs are Light Emitting Diodes, they can only be seen by the light they give off. LCDs are Liquid Crystal Displays, they do not give off light on their own and can only be seen by the light that shines on them or through tham. The back-lit LCD screens on computers and TVs are quite a bit different from the typical reflective types used on meters and wristwatches. The reflective type of LCD is usually very readable in sunlight, being very black on a gray background. The typical LED display gets very washed out and hard to see in bright light such as outdoors, since all it can do is emit light. It has to be a very powerful and expensive LED to be seen in sunlight.
  3. Before you go spending a lot of money, you might want to spend a few days reading posts here: http://www.diyaudio.com/forums/ Check out the Chip Amps forum in particular.
  4. I built my own bench power supply last winter/spring. It is a variable voltage supply using a circuit from one of the National Semiconductor datasheets using an LM350T regulator. It works pretty good, except when first turned on the voltage will not be what it was when it was turned off. This is because the voltage drifts upward for a while after it's first turned on. The drift is not terribly huge (in the 100-200 mV range), but it is annoying. After being on for an hour or so, it no longer changes and is rock steady from then on. I am assuming this is some kind of thermal drift. What could cause this and how could I fix it? I only use this supply for low power work, it's very rare that it must supply over 750 mA, usually less than 500 mA, and its set up to put out 1.2 - 20 volts. The transformer is a toroidal type, 30 VA, 2X18 volt, the rectifiers are 1N5408 discretes in a full wave bridge. There are 2 electrolytic 3300uf 35 volt filter caps. The voltage adjust pot is a 10 turn wire-wound type. It has the usual other capacitors and protection diodes. I think all the other caps except maybe one electolytic on the output are polypropylene types and all the resistors are all 25-turn trimmers. Everything after the transformer is on one pc board (home-made), The LM350T has a heat sink, but it is not huge. If more info would help, let me know.
  5. I'm pretty sure those are the BGA type (Ball Grid Array), I don't see any way you could solder those by hand (at least not realistically). Reflow solder would be my guess as to how those must be soldered (though I am not an expert on that method or BGA chips).
  6. SOP = Squint Only Periodically TSSOP = Terribly Small, Soldering Operations Precarious QFN = Quite Frustrating Now TQFP = Terrible Quandary Finding Pins BGA = Better Get Aspirin SOT –23 = Somewhere On Table, 2 maybe 3 of them :)
  7. http://www.capitaladvanced.com/products.htm
  8. There is a product called "Surfboards" which are very small pc boards with pins along one edge and various multi purpose patterns etched on them. You solder your surface mount component to the Surfboard, then you can plug it into any standard type breadboard. These are not very expensive. Most larger electronic suppliers should have them for sale. Maybe one of these would work for you.
  9. I put a fuse in the transformer's primary, but nowhere else. There is not much room for the manufacturer to have put a fuse in the meter, good idea though. meter When the wire came loose there were sparks and popping and clicking noises. The wire could easily have hit other places on the back of the meter while it was bouncing around as the back of the meter is open and not enclosed. The 7107 chip is in a socket, and I have tried replacing it as I have several of those chips, but it did not help. The good news is that I may have found out why the meter did not work correctly in the first place. The new meter should arrive sometime next week, I will find out for certain then. - Rick
  10. The meter won't blow if you short its supply? But I am pretty sure that is what happened. The negative power wire came loose and touched the positive connection. Meter will now only read -1 on display. Maybe it also touched something else or something else went wrong. Whatever, meter is now not working. I will look again and see if I can find some other problem though. I may have had some other connection wrong also, as I was doing this late at night and was pretty tired. New meter is on the way and will be here next week, will just have to play with something else until then.
  11. Yes, as I said in the original post, it would be two totally separate regulator circuits, by circuit I mean the whole thing, rectifier, filter caps etc., not just the regulator chip. Tonight I breadboarded up a 5 volt regulator circuit and connected to the transformer secondary of the variable power supply and it did work fine. Unfortunately, before I could test whether the meter gave stable readings with this set up, a wire somehow came loose and shorted the 5 volt supply. It didn't hurt the regulator but sending 5 volts to the meters ground connection seems to have broken it. Now I will have to order a new one. Oh well.
  12. The reason I want to try this is because I need to power a digital panel meter (19.99 volts) for my variable supply, it is a "common ground" type. It requires 5 volts, so I can't power it from the variable output of the supply because at times the output voltage could be too low to run the regulator. I tried powering the meter from a 7805 tapped in to the unregulated input to the variable power supply, which worked fine unless the power supply's voltage was adjusted above about 11.5 volts, then the panel meter's reading would begin to start jumping around and became unstable, and even when the variable output was adjusted to maximum (19.9 volts) none of the meter's readings were over 13 volts. It seems maybe common ground mode is not too happy with too much differential voltage between the meter's supply and the voltage being measured ? The meter works perfectly reading the power supply's output voltage if it is powered from a separate 5 volt bench supply, all the way up to 19.9 volts the readings are correct and stable. Because of this I thought to put in a separate supply for the panel meter, but there is no room for another transformer. The meter uses a maximum of 75 ma, so I could build it a tiny regulated supply of its own powered from the same transformer, and maybe get enough isolation to get rid of the unstable voltage readings.
  13. Is it possible to run two regulator circuits off of the same transformer secondary? One would be a LM317 and one would be a 7805 type. Everything about the regulator circuits would be separate, from the rectifier diodes to the output. The only thing in common would be the secondary of the transformer. Thanks.
  14. I was reading another thread where this subject came up. I was wondering what would be a good way to test if an old electrolytic capacitor was dried out or not? Maybe "dried out" is not the correct description, as I have heard of being able to "re-form" electrolytic capacitors I am specifically interested in out-of-circuit testing because I have a number of Panasonic large value electrolytic caps that have never been used but are over 10 years old (TSU series). One of my computers is 8 years old and I still use it with no problem, I even have one that is 12 years old and still runs with no problems, maybe these caps last longer than we think or is it just the quality of the capacitors used?
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