The Sansui Corrosive Glue Problem

While I am restoring this lovely AU-717 amplifier, I felt it was worth discussing the infamous Sansui corrosive glue problem.

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

The amplifier I am currently working on is no exception and several parts are so badly damaged that they almost fell off the board. The brown glue was used to hold larger parts firmly to circuit boards and does a good job of that.

This board is badly affected by the corrosive glue

However, it seems long-term testing to see what would happen to the parts held down by the brown glue over many years wasn’t done. The result is a large number of problems caused by the glue eating through components.

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, you need to remove it carefully from boards and parts. Leave as little remaining as possible remaining. You should also carefully examine the leads of any parts that have been exposed to this compound and look for signs of corrosion. Replace affected parts where necessary.

The amp I am restoring for my customer needs many new parts, some due to damage caused by this corrosive glue. I will also replace other parts that have degraded over time, like some heat-damaged caps on several boards. The following photos depict the nature of the problem in this otherwise pristine Sansui AU-717.

This is what I’m talking about. You can see the green oxidised copper on the remains of the resistor, between the two capacitors. Both capacitors also need replacing!
Yet more polychloroprene glue, and another damaged diode next to the capacitor that was glued down.

5 thoughts on “The Sansui Corrosive Glue Problem”

  1. Nice work there Mike. I have never had that in my Technics amplfiers but a NEC CD player from the 80s had that glue, caps damaged, transistor, ate legs from a regulator. I have fully resorted it now and works a charm. That is some nasty glue. Looks a lovely amp the Sansui, never had one but I like the layout of it

    1. Hi Sam, good work fixing your CD player. Yes these Sansui amplifiers are extremely well designed and engineered, apart from some production engineering decisions like using that glue!

    1. Hi Jack, I’ve emailed you about this so hopefully you received that message. Prices vary somewhat according to the condition of each individual piece, whether new main filter capacitors (expensive items) are required, level of corrosion of boards etc. It is best if I inspect the equipment and then give you an estimate. Be aware that there are really only one or two people in Western Australia who work on gear like this to the standards you see here on these pages. There are some very poor operators out there and you absolutely don’t want someone like that working on gear like this! Regards, Mike.

Thanks for reading, leave a comment and let me know what you think!