Recently I had occasion to dig out one of my VAXstation 4000 VLC machines. Before using it I decided it was prudent to check the power supply, a H7109-C, to make sure there were no leaking or bulging capacitors.
It was a good job I did, because one of the capacitors had leaked. So I took the opportunity to check all the electrolytic capacitors and found several that had a high ESR. I have now replaced them all and cleaned up the leak. I also noticed that a ceramic disk capacitor was split (see photo). This capacitor did not measure a stable capacitance, so I replaced that too.
In the photos below I have numbered the replaced capacitors and give their values here:
- 39uF 16V
- 330uF 25V
- 330uF 25V
- 470uF 25V, this is the one that leaked
- 330uF 25V
- 330uF 25V
- 3.3nf Ceramic Disk, this is the one that is split.
After replacing the capacitors I powered on the machine and it worked fine. The ripple was about 50mV on both the 5V and 12V outputs.
Here is the machine with the cover off:
Rob's Old Computers 