![]() There were two electrolytic capacitors on the board which I pulled, measured and replaced. Hopefully not making a rookie mistake there.ģ. I'm checking the voltage by connecting the DMM to the incoming black transformer lead, and then probing the VSS and VDD pins with the red lead. Both pins also seem to have about 4 VAC on them. If the TMS1952NL is in fact pin-compatible with the MM5316 clock chip, then the VSS pin is seeing just short of 9V DC, and VDD is -16V DC. I confirmed no shorting between secondary and primary.Ģ. ![]() When checking voltage between the red wires and black, both red wires are putting out 10.5V. ![]() The clock board is powered by a transformer which has two red wires and one black coming out. Below are some of the things I've done so far:ġ. This provides a decent brightness but using some power calculators to see dissipation requirements for resistances that seem to be in line with the old resistors, and it looks like they would have been required to dissipate anywhere from 2-4W, well over the 1/4W rating of the original resistors.Īny guidance on what I should check next would be appreciated. I've since temporarily connected two, 100 ohm 1W resistors in parallel to give me a resistance roughly in the middle of the expected range, and with a bit more ability to dissipate power. The burnt resistors were in series, and I believe they were in the range of 10 ohms to 100 ohms. I measured the voltage between the points just before and after where the resistors were, and I am seeing 12V DC. Problem is I'm too new to know which the answer might be so I'm hoping for some guidance here. To me this suggests either something else isn't working right in the circuit, or it was a bad design from the get-go. The main question is, it seems to me like the resistors that burnt are being made to dissipate quite a bit of power, and yet the originals where only 1/4W each. The main clock chip is a TI TMS1952NL, a 40-pin DIP, and I cannot find a datasheet for it, but after probing around it seems like it might be pin-compatible with the MM5316 which I could find a datasheet for.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |