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  1. Tha fios agaibh

    Lm339 output

    I repaired a board yesterday where I had a bad optocoupler driven by a LM339N. I was expecting the output to be 0V (ground) when triggered. (When Neg > Vth) Instead it was about 0.5v. From pin 3 Vcc with respect to pin 12 gnd I got 15v. From pin 3 Vcc with respect to output pin 2 I only got...
  2. Tha fios agaibh

    Meter screw up a fluke?

    I always trusted my fluke meters but i noticed my 87iii screwing up reading lower resistances. I comparitively checked a resistance of 467Ω and got 467Ω on my fluke 115 and fluke 87v but my fluke 87iii said O.L. I checked it again and it was right but read .467k Suspecting the autoranging...
  3. Tha fios agaibh

    Chip ID on Hunter water controller

    Trying to repair my Hunter output module and suspect the IC on bottom right is bad. Searching 9943HAB yielded no results. The logo looks like Microchip. Is there any chance of finding a replacement, ... or must I pony up $150 for a new board?
  4. Tha fios agaibh

    Monitoring Rs232 data

    I'm trying to diagnose a serial communication problem between a host computer and client printer. It's a RS232 full duplex connection from a DB9 com port on the PC through a crossover cable to the DTE printer. All connections and com settings look normal. I thought I'd try reading the data...
  5. Tha fios agaibh

    Chip ID...Who am I?

    I came upon this tiny 24 pin smd chip trying to repair an android tablet and can't find anything on the web. Is it a TQFP package? Any idea? Markings are: MP65 TO69C1 L1314D
  6. Tha fios agaibh

    Led color control

    My Daughter bought some led strip lights for her room. Problem is, they came with a controller that has two plugs designed to independently feed each of the 2 spools of strip lights. She wasn't happy she couldn't have a long continuous strip of lights so I spliced the 2nd spool into the first...
  7. Tha fios agaibh

    Use for old scanner?

    I've got an old police scanner that's been kicking around for years. It's not of much use now a days with trunked and encrypted communication becoming the norm. Any ideas of how I can use or repurpose this radio, or should I just scrap it? I was hoping there might be some sort of hack to turn...
  8. Tha fios agaibh

    Spare time for tinkering

    I imagine I'm not the only one that feels this way, but there doesn't seem to be much time left for electronic projects after work, family time and keeping up the maintenance on our house and property. I have projects that have literally sat on the shelf for years that I'll probably never get...
  9. Tha fios agaibh

    Reflow Bga chip.

    I picked up a nearby scrap plasma TV for a few bucks with a pink and green pixelated screen. I found the graphics processor, added a little flux around its edges and heated it up in a circular motion with my hot air gun......and voila' , it fixed the problem, but I realize this is likely just a...
  10. Tha fios agaibh

    Windows 10 website blocking

    I sometimes edit the Windows "host" file to block the youtube website for the kids. Then I have to put it back. What would be even better, would be if I could have the website time-out after say 30 min or so. Can anyone computer savvy help me write a script or batch file that would do this...
  11. Tha fios agaibh

    Unknown capacitor.

    Fixing a 120v electric paper punch for a friend. I believe the problem is that square blue capacitor C2. Its the first component after the line fuse, and is parallel with a 1meg resistor. It only reads 678nf (out of ckt) and is only passing about 3v on to what I believe is a smt bridge...
  12. Tha fios agaibh

    RC receiver failure

    My boys RC boat quit working earlier this summer. I found and replaced a bad/unresponsive receiver board and it worked fine for a while, until the exact same thing happened again. I then noticed a few open spots on the pcb and am thinking they omitted (to save 1c per board?) the flyback diodes...
  13. Tha fios agaibh

    Light show and Phone power questions

    Last weekend an ice storm caused a tree to fall directly across a 15kv utility line in our yard. After an impressive light show, about 700 of my neighbors and I were left without utility power for a day. My backup generator kicked in a minute afterwards to give us household power, but there...
  14. Tha fios agaibh

    Battery charger questions

    Scenario 1: Someone asked me to repair a golf cart style battery charger. I found there was nothing wrong with the charger itself. The charger was not turning on because it didn't see its minimum cut-on voltage because the batteries were too dead. Q1:Why do they design a charger with a cut-on...
  15. Tha fios agaibh

    Keyboard no sound

    My daughter is bummed out that her Huntington KB54 keyboard died. Powers up, display responds to functions but has no sound at all. I found power 12vdc power supply failed and was outputting 24v (unloaded) I replaced with new ps and opened it up and and verified 12vdc at amp board and 5vdc rail...
  16. Tha fios agaibh

    What's wrong with circuit?

    I got this video link from bluejet for a remote control power circuit, but I wasn't able to get it working. It was originally posted under projects, but I'm reposting here because I could really use some circuit help here. Here's a sketch of receiving circuit using values given in video...
  17. Tha fios agaibh

    Remote sensor on powerline

    I'd like to hook up a remote sensor at end of my driveway to alert when someone arrives. It's very far away from the house; about 500ft or 150m, so naturally I don't want to run a cable out there. Second option would be to use a RF transmitter but they can be prone to interference and it'd have...
  18. Tha fios agaibh

    Please explain circuit

    I saw this video on YouTube about a password switch. I thought it clever, but I assume easily hackable by simply pushing any button s1 thru s4, 4 times without hitting a reset button (pin 15). How does pin 14 (clock) see Vcc by being fed from the outputs that are presumably low?
  19. Tha fios agaibh

    Power rail names

    It seems odd to me some of the identifying terms used for power rails; like Vcc or Vdd. Yes, It makes sense when more than one collector or drain are similarly connected to the positive rail, but what about when you have a circuit with both mixed bjt and fets, or mixed N type and P type...
  20. Tha fios agaibh

    Most common failure survey.

    I know its impossible to say specifically because circuitry and components vary widely, along with the conditions and applications. But, generally speaking; Is their one type of component or failure that you see most often in electronic repairs? Example, leaky electrolytic capacitors...
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