Best transparent glue for illuminated piano key

[high_vacuum_house]

Good evening,
I am restoring a Saba Frieburg automatic 8 which has LES bulbs under the piano keys which illuminate the waveband key when pressed. It is quite impressive. One of the keys has broken off its actuator mounting lugs inside the key. It must have been pressed very hard. As the key is hollow and the broken bits are lone gone, I was thinking the only option is to fill the key up with a transparent araldite and push the key back onto its actuator and let it set. It would need to be fairly transparent when set to allow the light from the bulb underneath to illuminate it when pressed.

Does anyone know of a suitable transparent araldite type glue that would work here.

Many thanks,
Christopher Capener

[Silicon]

I have never used Araldite Crystal but they claim it sets clear.

[high_vacuum_house]

Yes, that looks like it should work looking at the specifications and applications. There is some at our local Toolstation as well. I will get one tomorrow and see how it turns out.

Many thanks,
Christopher Capener

[Radio Wrangler]

Mix up a bit and try it on something non critical. let it cure and evaluate before committing anything irreplaceable.

David

[cmjones01]

Another adhesive I've been recommended for optical applications is Loctite 3430. It's a reasonably quick-setting two-part epoxy. I used to use it for assembling lens and holder assemblies for high-powered LEDs and it's stood the test of time: I've got lights assembled more than 20 years ago with it which are still fine, and I still keep it in the workshop as a general-purpose epoxy.

It also complies with my belief that an adhesive will only work properly if it's got a number

Chris

[Uncle Bulgaria]

I can't visualise the design, but if the actuating parts are important perhaps it's possible to cast a new key from one of the others? I've been using GlassCast which is optically clear and UV resistant. The Radiomuseum pictures make the keys look slightly creamy in colour, which could be applied as a tint to the mix. If it's just a clean break then one of these clear epoxies sounds a fine plan.

[high_vacuum_house]

Good evening,
I bought the Araldite crystal and tested it out on an old plastic part and it adhered well and remained completely transparent.

I gave the key a good clean inside and out. There is a brown stain on the front where someone has repaired it with something else in the past and has stained the plastic permanently. Luckily the lower half cannot be seen as it is below a metallic moulding trim which fits around the front of the keys.

A plastic component bag was taped up behind the key and some tape was used to ensure the knob stayed in the correct alignment during curing.

The knob was half filled with the Araldite and carefully fitted. The chassis was tipped up vertically, so the Araldite couldn't run out and was left for several hours to cure.

With the tape and bag removed, This looks like a completely successful repair as the repair cannot be seen and the key works as it should.

Just to note, the key which was broken was the one which selects VHF FM needs slightly more effort to press than the AM keys as it has to push across a mechanical clutch which selects the rotation from the tuning knob to either the AM variable capacitor, or the variable inductor of the VHF front end.

You can see the small LES lamps behind the knobs in the last picture. Pressing one of the keys down causes a contact to the right hand side of the bulb to connect to chassis causing it to light up the selected waveband key. The repaired key is the one with the brown patch on, next to 31-35 on the dial glass.

Christopher Capener

[vinrads]

Well done Christopher it's nice when a plan comes together, it should now stand up to the extra pressure needed as described.
p.s It was nice to see you again yesterday .Mick.

[high_vacuum_house]

A couple of pictures to show the key lights in operation (whilst listening to radio 3!)

The inverted T control below the band selector keys is a tuning control slider. push it to the right lightly and the tuning knob rotates slowly clockwise (via the auto tuning seeking motor) Push it further right and the action is faster clockwise. The opposite effect takes place when pushed to the left.

The EM34 is completely flat and a new one is needed. Looks a right nightmare to replace even with the chassis on the table! There is a pulley with indicator around its front edge, this shows the position of rotation of the ferrite rod antenna (adjustable with the rear left hand knob) A microswitch turns off the ferrite rod antenna and the green SABA logo at each end and brings in the external aerial sockets. Pretty complicated!

Musik and Sprache windows on the dial below the knobs. You can select either music or speech from the end keys, which a relay then changes the tone control circuit and lights the appropriate lamp.

Christopher Capener

[RadioRich]

Hello Christopher,
That repair was impressive it looks great !

I never used that product but I have use Alumilite brand to cast parts thou.

Sincerely Richard