I got an Apple II Plus which didn't power up.
I started with the power supply. Visual inspection of the Astec AA11040 shows that it's in pretty good condition.
However when I turn it on there was nothing on the output. First issue I found was that the fuse was blown. This would indicate that there's likely something else wrong with the power supply.
I did a quick check across most of the components for shorts, but nothing turned up. I figured I would give it a go to see if the fuse blows again. The power supply did turn on fine, and I was getting correct voltage across all output rails, however I also noticed that some components were getting hot which should not be.
Specifically, C4 was getting really hot (>70°C). C5 was also getting moderately hot. This was really out of place, as electrolytic capacitor should not get hot during normal use.
![160545[F].jpg](https://tinkerdifferent.com/attachments/160545-f-jpg.5522/ "160545[F].jpg")
C4 and C2 run in parallel, and act as smoothing capacitors after the rectifier. Since only one of them is overheating, I'm pretty confident that the capacitor is the culprit here.
My initial plan here is to do a full re-cap on this board. I didn't have the board ON for more than 30 seconds. I'm sure if I leave it ON for a couple minutes something will pop.
I've also noticed the load resistors on the output have started burning the board itself. Not sure why this is occurring or if it's expected. I'm planning on replacing these three as well.
Lastly, I've also noticed that 2 of the polyester capacitors are cracked.
C1 says "0.1 630", which I guess is 0.1uF 630v, data sheet shows "POLYESTER CAPACITOR 0.1 UF 400V" so that's straight forward. Will use ECQ-E6104JF as replacement.
But C20 is not on the schematic part list. I think it says "0.1 160" which I assume is 0.1uF 160v. Image below, I plan on using ECQ-E2104JFB, I hope it's the right replacement.
I started with the power supply. Visual inspection of the Astec AA11040 shows that it's in pretty good condition.
However when I turn it on there was nothing on the output. First issue I found was that the fuse was blown. This would indicate that there's likely something else wrong with the power supply.
I did a quick check across most of the components for shorts, but nothing turned up. I figured I would give it a go to see if the fuse blows again. The power supply did turn on fine, and I was getting correct voltage across all output rails, however I also noticed that some components were getting hot which should not be.
Specifically, C4 was getting really hot (>70°C). C5 was also getting moderately hot. This was really out of place, as electrolytic capacitor should not get hot during normal use.
C4 and C2 run in parallel, and act as smoothing capacitors after the rectifier. Since only one of them is overheating, I'm pretty confident that the capacitor is the culprit here.
My initial plan here is to do a full re-cap on this board. I didn't have the board ON for more than 30 seconds. I'm sure if I leave it ON for a couple minutes something will pop.
I've also noticed the load resistors on the output have started burning the board itself. Not sure why this is occurring or if it's expected. I'm planning on replacing these three as well.
Lastly, I've also noticed that 2 of the polyester capacitors are cracked.
C1 says "0.1 630", which I guess is 0.1uF 630v, data sheet shows "POLYESTER CAPACITOR 0.1 UF 400V" so that's straight forward. Will use ECQ-E6104JF as replacement.
But C20 is not on the schematic part list. I think it says "0.1 160" which I assume is 0.1uF 160v. Image below, I plan on using ECQ-E2104JFB, I hope it's the right replacement.
