Beomaster 4400 Type 2419: Power On/Off Switch Woes

This Beomaster 4400 would be ready to resume testing again if only its power on/off switch would work properly.

If you remember the original power on/off switch caught fire and had badly burned contacts.

For the replacement power on/off switch I pulled a switch out of a spare parts, donor Beomaster 4400 unit. I had no idea of the condition of that unit and when I opened up the power switch it had some pitting but overall wasn't too bad. A little cleaning and it was ready to install and that should have been the end of it.  It wasn't of course :-).

While the replacement switch initially measure a nice 0.1 ohm to 0.2 ohm "On" resistance when it was installed and in use the switch became unreliable and needed some fiddling with the buttons to get the Beomaster to turn on. Something mechanical was not right.

My next plan was to grab a second replacement, donor power on/off switch from another parts unit. The switch didn't look too bad until I checked it out with an ohmmeter. Off measured fine but the "On" resistance jumped around in the 100 to 300 ohm range. Not a good reading.

So I opened up this third Beomaster 4400 power on/off switch and it was about as badly burned as the first one.

Here is the third switch (second replacement candidate).

Very ugly and very disappointing to say the least.

I don't even want to try to clean that up.

When I reopened my first replacement candidate switch its contacts still looked pretty good but the switch contacts had shifted position so good contact was not being made. That explained the mechanical inconsistency.

I had to stop and think about my options.  I could really go for a nice 3D printed replacement switch about now.  Unfortunately that doesn't exist (yet).

My best chance here is to select my best contacts and my best plastic housing components to put together a solid working power on/off switch.

I think my first replacement switch attempt failed because I soldered too many connections to the outer terminals.  They heated up and then shifted internally which caused the poor switching performance.

This time I will make sure to make the other connections away from the switch and just attach two wires to the switch contacts. In addition I will use some heat protection while the contacts are soldered.

Here are my collection of Beomaster 4400 power on/off switch contacts.

If I turn the best set of contacts around I will have fresh new surfaces to mate for the power on switching. I will clean up the switch housing on the lower right to use in the new switch assembly attempt as it is the most structurally sound.

Another problem involving the power on/off switch that I will have to solve is remounting the switch on the switching assembly.  There are damaged mounting tabs so I will have to construct something to secure the switch when I mount it.