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Originally Posted by factory
Bit puzzled why you had trouble finding the LM317T, they are a very common adjustable regulator IC along with the the LM337T and aren't hard to obtain from reputable component suppliers eg Mouser or Digikey. It's possible you have a short circuit on the output of these regulated supplies and fitting a new one won't necessarily cure the problem.
Also not sure why R29-R30 would have burnt out, wouldn't the resistors around the main output attenuator be more likely to burn out if back fed from the MOSFET circuit you were testing, or were you using one the other outputs?
David
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I think Mouser had it, I did look but apparently I didn't see it or I would have ordered it. I'm not that familiar with either of those sites since I've always used eBay and I think I googled the part number when I looked on the mouser website and I think it was something to do with the way I searched for it. But for the other regulator, not sure which it was I had to order 400 pcs to get it. Because of your post and a second look, I'm more familiar with the site, But still don't fully understand it. I'm not sure why R29-29 roasted black, I thought the same and was puzzled when they was not burnt around the attenuator. I was indeed using the 50 ohm output.
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It shouldn't be possible for an LM317 etc, to get hot if just that faulty, as the only high-current path is from input to output - As it's an adjustable regulator, there isn't a ground pin, but an adjust pin connected via a resistor potential-divider to it's output.
So for it to get hot, there must be a fault elsewhere, like a short on its output.
Note: The metal tab on the TO-220 LM317T is the Output connection, so must be electrically insulated from any heatsink that is grounded.
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I did find a dead short where I replaced a diode, but I've repaired that, and I still see lots of heat. I Built the dual regulator circuit on a PCB and tested several of those regulators and then re-installed them back into the gen so I could better understand what was going on. It was a pain insulating the tab an the re-installation!
I have several problems going on, For example, I replaced Q8, This transistor still overheats, I removed 85% or the TTL/IC'S and I'm still having problems. I'm getting heat from a few different transistors. I did not think just by removing the IC's It would cause the Transistors to overheat, any thought on that?
I think because of my lack of perfections when soldering in the faulty rectifier diode it caused Q40 to get smoking hot so I removed it until I narrowed more of these problems down. Also, IC7 it's getting pretty hot so I replaced it, and it's still getting hot.. sigh.... I think the power supply circuit is good, I seem to be getting all the voltages, however without the heat sinks a few of the regulators will burn you. I'm trying the best I can to narrow this down, it's taking allot of time! I'm open for any suggestions, and will run any test recommended and report back. I plan on fixing this even if I'm 80 years old. I'm excited I have these units, but I'm also a bit worried because I haven't fixed it yet.