In 1980s, aluminum electrolytic capacitors with quaternary salt were used. It was said high performance and long life. Many companies made them. But about 5 years goes, they started leaking solutions that was high pH (having strong alkalinity). It was found that quaternary salt became alkaline belong long time use. That problems was not found in condensed test in labs. As a result, almost high performance caps in 1980 leaks in about 10 years. High pH caps not only leaks but makes short circuit. Then one day, PSU fires.

To prevent break down,we must need to renew all caps. But now, it is too late. Almost PSU is broken,isn't it?

We must replace not only caps but zener-diodes, photo couplers, some transistors, resistors, and so on. Ideally, all pars to be replaced but some parts was discontinued.

I researched succeeding parts, but it is imperfect. Any advices is welcome.

p.s. Original X68000 PSU seems not to use quaternary salt. But they are too old, so they should be replaced.

It has the same design as the PSU of Expert but features lower rated capacitors. It is recommended to use use the capacitor ratings which are mentioned in the Expert section.

Almost all info taken from: http://x68k.net/x68dengen/

All X68000 power supplies fail because of the capacitors. Here are a few common symptoms and solutions:

1. Main power is connected, front LED is glowing red but the system does not react to front soft-power switch. Check if ZD31 or anything around it is burnt. Replace ZD31 and all electrolytic capacitors. There are some cases when Q32 also needs to be replaced. In some rare cases PC31, PC51, PC52 also need to be replaced.
2. R35 rupture is caused when C31 capacity has decreased to the point that it is no longer able to supply constant voltage and current. In this case it is advisable to replace Q31, Q32, R35, ZD31.
3. The fuse gets blown if C9 is faulty. Replace all electrolytic capacitors, 4A fuse and check if there are no signs of damage to the ZD31 or near it.
4. Most parts though discontinued have generic replacements available. The only custom-made part is the transformer but it is very reliable and does not break easily.

Schematics

• X68000 Expert PSU Schematics

Schematics

• X68000 Pro PSU Schematics

• X68000 Compact/030 PSU Schematics

These are more tolerant. Their capacitors leak but usually do not kill anything and a simple recap is all that is needed.