The Sansui corrosive glue problem affects many vintage amplifiers and other equipment. Resolving the issues caused by this glue can be time-consuming.

You may be familiar with the scenario: over time, your favourite Sansui (or other) amplifier starts to develop faults. Maybe it won’t come out of protection, or maybe a channel becomes intermittent. These sorts of problems have many causes, but one common one is the infamous Sansui corrosive glue.

The Glue

Most equipment manufactured by Sansui, and others, during a certain period in the ’70s and ’80s, will be affected by a nasty, corrosive glue compound. It’s called polychloroprene and, in certain situations, it eats through components like an acid. It literally becomes corrosive glue.

Polychloroprene has been around for a long time – since 1931. It’s a powerful and long-lasting contact adhesive used in many industries. You can read more about polychloroprene and its properties in this fascinating article.

Many electronics manufacturers use polychloroprene glue to secure capacitors to circuit boards. It effectively reduces vibration and therefore improves sonic performance and reduces the risk of vibration damage.

However, it seems long-term testing to see what would happen to the parts held down by the brown glue wasn’t done. The result is a huge number of problems caused by the glue eating through components in gear from this period.

The Problem

That’s right, the glue these manufacturers used is corrosive or becomes so over time. I’m sure this was not well understood at the time, but it can create big problems. What happens is that the glue, whenever it touches tin-plated copper legs of components, literally eats through them given enough time and possibly some environmental conditions conducive to this process.

The damage can be so severe that I’ve worked on equipment where components have fallen off the board when I’ve touched them. The amplifier I was working on when I originally wrote this article was no exception, several parts were so badly damaged they were just hanging off the board.

Affected Equipment

I wish I could say this is just a Sansui corrosive glue problem, but it’s not. Various manufacturers, notably Sansui, Luxman, Marantz and others used it extensively. There’s no doubt that Sansui loved this glue, it causes havoc in virtually all of the AU series of amplifiers, plus a whole bunch of other stuff they made. But it’s also found in a whole bunch of other gear, especially from Japan.

The Solution

This corrosive polychloroprene glue will destroy circuit board traces, eat through component legs and even dissolve the parts themselves. Anywhere you find this dark brown glue impinging on component leads, it must be carefully removed from boards and parts.

If the glue is hard and crumbly, I find it easiest to scrape it off with a hard tool, like a flat-blade screwdriver for example. If the glue is still pliable, it can be much more difficult to remove. Often a combination of acetone and a scraping tool will work best in these situations. The idea here is to soften and loosen the polychloroprene before scraping it off.

One must also carefully examine the leads of any parts that have been exposed to this compound for signs of corrosion. Replace affected parts where necessary and if in doubt, err on the side of caution and replace the part. The Sansui AU-717 amplifier I restored for my customer which prompted me to originally write this article needed many new parts.