I've recently restored a Pioneer SA 710 (~1980 blue line integrated amp). After replacing the main capacitors (originals were down by 30% in terms of capacitance), replacing electrolytics in the power supply and in the pre- and main amp section, I was quite impressed by the sound that came out of my Special 40s. The switches seemed noise free, apart from the input selector which was cutting in and out, especially on the Aux position. With no significant improvement after several attempts of flushing the switch from the outside with electronics cleaner and Deoxit red, I decided to disassemble the switch.
Overall, it is a relatively straightforward job. The specific switch (Alps ASX 114) is used on many other amps of that time so if you want to attempt this, here are a few learnings:
Overall, it is a relatively straightforward job. The specific switch (Alps ASX 114) is used on many other amps of that time so if you want to attempt this, here are a few learnings:
- be careful when removing the blue plastic push pull connector that runs between the selector knob on the front panel and the actual switch in the rear of the amp. It is connected to the switch by 4 plastic snap-on clips (one on each corner). I managed to safely remove the plastic connector by rocking it to one side. Once one or two of the clips come undone it is easy to remove the plastic cable from the metal switch housing
- fully desolder the pins. the fit on the Pioneer PCB is ultra-tight (even without solder) and any tiny amount of leftover solder will make the removal difficult and/or lead to damage on the pins. I managed to break off a tiny bit from one of the pins but it was still long enough to make proper contact when I soldered the switch back in
- The switch is held together by 6 metal tabs which are quite close to the pins. I used a cheap China electronics cutter to lever them open. The cutting edge easily slides under the tab and the cutter can then be used to gently pry the tabs up without damaging the contact pins (not great for the cutter so don't attempt this with your Knipex)
- Once the switch is open, remove the plastic cap which transfers the motion of the blue plastic cable to the moving parts of the switch
- Take photos! Note the orientation of the 4 small gold/copper tabs in relation to the front of the switch
- The switch contacts are silver plated and the silver will get a patina over time, especially on the outside positions of the switch (where Aux sits on the SA 710). Despite trying for 10 minutes, no amount of deoxit red fully removed the silver oxidation. I used a non-abrasive silver cleaning cloth and got very good results. Don't forget the inside areas of the switch (in total 4 surfaces to clean)
- the four little contact tabs that ride on the sliver-plated switch body seem to be gold plated and had very limited oxidation. I used a pipe cleaner with Deoxit red to clean them on the inside, the little wire of the pipe cleaner will help spread the tabs for cleaning but is thin enough to not permanently bend the contacts open
- Re-assemble the switch (with a little deoxit applied) and carefully close the tabs after making sure the internals move freely. I used a flat head screwdriver with anti slip grooves on the tip (see photo) to ensure I don't slip and massacre the pins when bending the tabs
Attachments
tbh I bought the first silver cleaning cloth I could find on Amazon (in the UK): Goddards long term polish cloth. I don't think it is the best out there (it took me about 15 min to clean the switch) but it did the job and it wasn't very expensive. I'd reckon any silver cleaning cloth will do s long as it is not abrasive
