I have an Amiga 500 PSU which is a bit unstable. Sometimes my Amiga 500's don't start when using this PSU.
I measured the voltages of the PSU (when connected to the Amiga) and the 5V rail was a bit low, and slowly rising. When the voltage was under 4.8, the Amiga wouldn't start. So in order to troubleshoot, I started with drawing a schematic of the PSU. The schematic is a work in progress, I change it as I find errors, so the best version is at GitHub:
https://github.com/archstanton1862/A500-PSU .
So, in accordance to the schematic references, I measured the parts that are involved in the 5V regulators feedback: 5V reference was 5.008V, excellent in other words.
5V R2 = 1.500k
R4 = 4.702k
Internal reference R1 = 1.498k
R5 = 4.700k
These resistors show signs of getting hot, so I measured them swell.
R6 = 179.8
R8 = 179.9
The first idea I had was to replace the output transistor. It was difficult to find the exact replacement , so I ordered a D45H11G (instead of the original D45H2). This did not change the faulty behaviour.
Finally I tried swapping the regulator IC, SG3524, to a new one. I didn't think this would work, but actually it did. Voltage in a running Amiga 500 was measured to 4.93V and this was enough for stable activity.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg5vEa2hqzeVzoINjx_9-05rL909nDsLWHKe9v6oXwsvmP6yBV9v-dIT1yPEz9_VQNeCB65qqVdt0L3d7zfHkLdFsnACKX9P99z7eVNOHiAC4g4QCCja_JEvbXkclNddl0HZ2QfcScP04Jn/s320/IMG_1085.JPG) |
PSU with replaced regulator IC (SG3524) |
Grazie per la pubblicazione , potrĂ servire ad altri appassionati!
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