Search results

Well then nice job on your schematic update! I hope those can get rolled in to the published one. The values I see are on an LC, my HD wasn't always starting up right so those may have been with power to the drive disconnected but I believe it was connected. Those voltages also look in line...

My supply is fully assembled, and the original work is not mine so I can't make any corrections. But I can say R2, R3, and R15 are all connected to the same high side of C5 (the rectified input voltage from CR1). For the output voltages the negative is the result of the positive 5V regulator...

Welp, I guess replacing the C78N05 with an ST L78M05ABV fixed the problem, this is what now see: Here's my minor contribution to this thread which I found really useful! Thanks to @SuperSVGA! Here's two corrections to the schematic. As discussed previously, the pin numbers for IC51 (C78N05)...

Thanks, I had recently picked up some 7805s to compare against what's in the board and the 75C05 does appear to be the standard positive 5V part, so installing found I didn't have an LC board nearby so checked it unloaded and found -5V was still all over, the other voltages did what I'd expect...

Can anyone confirm the transformer outputs are basically just two at 5V each? I've done everything except start feeding the inputs to confirm and all I find appears to be two coils or one coil with wired to 5 pins. I wasn't able to see how the voltage feeding the 5V line is negative since pin3...

One of several nice things about the Astec AA16-251 version of this supply (which also needed a restore after the two 120uF caps C17 and C20 were found to have 0 capactiance) is the wires are soldered directly into the board with silkscreens! Orange: +5, Yellow: +12, and Blue: -5. This is also...

@ben68k since you're actively digging around in the circuit, could you do me a favor and check the voltages on the C78N05 (IC51). I can't figure out the input voltage (pin1), (with pins numbers 1, 2. 3 when looking at the label side). As noted a couple posts early I am unsure questions about the...

Has anyone found a modern equivalent of the C78N05 (IC51)? I've got the unstable -5V output after recapping (and looks like there may be electrolyte or something else on the board, cleaning has been in progress next would be depop and clean or ultrasonic. But before doing that I started looking...

Did anyone with the unstable -5V condition get things resolved? It looks like RetroViator found a unrelated fix. I'm with chuck42 unloaded goes all over while +12 and +5 are rock solid. I've cleaned the board several times, but didn't depopulate the entire board which may be needed. I saw the...