So my power supply finally came in today so now it’s time to test. All was well for the first three measurements but the blue point is hanging out at a -14.95 and I’ve checked the joints on the trace running all the way back to the power input. What else should I be looking for? I can post pictures when I’m back in the cave. Thanks
What are the voltages on each pin of the 7908?
top pin: 0, Mid pin: -15.28 bottom pin: -14.68
Are you sure you haven’t swapped some of the regulators?
Is the TL072 inserted on the mobo?
I just checked and double checked the regulators and I haven’t put TL072 in yet.
Try putting the TL072 - you won’t damage it, and it might provide a bit of load to stabilize the negative rail.
It’s hanging out at -14.50
I started trying to test my ac adapter and the results seem to be that it’s putting out over 11v and not the supposed 9, could that affect it?
No, it’s not a problem…
For what it’s worth, my adaptor does the same. Unregulated power supplies should drop down to the appropriate level under load when they are actually connected up to a circuit.
here are some photos of my board. If its too dirty, I can apply some flux remover. I do remember one of my JP#'s losing a pad but solder stayed on fine. Think I should remove the solder on any particular ones to find that potential joint?
If you put a 10k resistor between a -8V point and ground to add a bit more load, does it help bringing the -8V rail down?
for testing purposes, do i need to solder that temporarily? i tried just giving two points contact but no cigar. this is the easiest place I’ve found, you may know far simpler ways
You don’t need to solder anything, just stick the resistor in the voicecard connector.
Tried it with no success
So an observation has risen; when I test any of the -8v rails, my multimeter hops to -7.98v for a very very brief moment and proceeds to jump further to the -14.50. I don’t have another multimeter to see if that’s just how it’s reading it. But it is very consistent. Any thoughts?
you’re measuring between -8V and GND?
sure you have it set to VDC and not VAC?
Good news! The culprit was a backwards D4 that I couldn’t easily see because of the heatsink. Voltages are measuring beautifully. Too bad, I foolishly forgot to order the 6n137. I’ve found a vishay one on digikey that seems alright though it has lower forward current. I’m not sure if I should post this in BOM because this could be a good replacement for the dead digikey part number