Lasonic Function Switch Gear problem SOLVED by Trommelmops

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Lasonic TRC-920

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A solution to the infamous function switch broken gear that plagues the Lasonic TRC 920 and 931's Tape/Radio/Line In as well as the AM/FM selector switch has been found.

Over the last month I have been working with Trommelmops to solve this problem and with the help of DOCS it has been solved.

As you will see below, Trommelmops has managed to meticulously recreate the gear out of brass as a direct replacement.

SPECIAL THANKS TO DOCS for the assist! He mailed Trommelmops a spare switch for him to make the final measurements which helped him complete this job.

So, to start with. I mailed T.M. a broken gear that I had used in the past as a template to make gears by hand out of plastic. You can see two video's HERE and HERE which will help you replace the gear in the switch.

As you can see, the gear is not just a simple wheel with teeth. It's a complex design with bump stops and limiters. You can also see where the gear broke. It snaps in a weak spot between the teeth. There is such little material there, that it makes gluing it or repairing it virtually impossible.

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Here you can see T.M. has taken bar stock and sliced long groves in it to make the teeth.

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Next, you can see where T.M. made the holder, where the gearwheel and the cam are put on together in the right position.

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He simply sliced the bar stock like a loaf of bread and he had gears!

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Now, brazing on the tab

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Next came fitting to the switch...

The gear is placed back on the knob shaft

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And the knob shaft placed back into the switch case

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The original gear was held in place by flattening the end of the shaft onto the gear. But there is a better way of doing this. So T.M. drilled and threaded a tiny hole in the side of the gear and used a M2x4mm screw to lock it in place. This does require a hex key size 0.9mm to tighten it. If you don't have one, T.M. can make you one for a small additional cost, just ask him when you order.

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The last thing your going to want to do is put some sort of grease on the gear and track to keep it lubed.

And there you have it...

If your interested in a replacement gear for your function switch contact Trommelmops via direct PM.

The reality of the situation is this...

I have lost count on how many of these I have personally rebuilt. It's a job that you only want to have to do once, because it's a PITA to do. I have tried gluing the gears with super glue, epoxy, JB weld, hot glue guns and plastic weld. Nothing works. There just isn't enough materiel between the gear teeth to hold it together. So your left with only a few options. Replace the whole switch with a working switch from another Lasonic with another 35 year old plastic gear, make your own plastic gears as I show in the video's listed above or for a very reasonable price (ask Trommelmops for a quote) you can quite literally double the value of your 920 or 931 by fixing it's Achilles heel once and for all!

A HUGE thank you to Trommelmops for taking the time to engineer this gear, as you can see in the pictures, this is a massive undertaking.

Thank you again to DOCS for shipping Trommelmops a spare switch for him to use for measurements.

It's these group efforts that make it possible to keep these old radio's going.
 

T-STER

Member (SA)
Very cool, going to order one now for my 931 :D

Trommelmops is helping breath new life into our boxes :thumbsup:
 

floyd

Boomus Fidelis
Epic!.
It's like having the impossible happen.
We know how tiny these gears are so its all the more impressive.
A master craftsman in every way.
Awesome and thank you for doing this badly needed work.
 

Trommelmops

Member (SA)
Oh my......

It was not easy to make it happend....and the module was milled with a M0.7 module gear cutter....cause you need the involunt tooth....

And the gearwheels are blasted to clean up and make the surface smooth.

I have also made some little hex key driver with 0.9mm for this purpose. I have took a 1,5mm hex driver and then i have grind them all in my mill.....

was tricky, but the result is that the hex driver fits perfect :-)

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Notice for all: Dont torque with to much force! :nonono: The screw is tiny and the hex key driver will broke then!!!! :yes:

Not the gearwheel! :no: This is strong enough :yes: .....

And this is also very important: Dont grind or file on the gearwheel!!! This is forbidden. The shaft is Alu and its the only one what you have to file!

To feel if its ok you see, when the shaft is easy slide through the shell! Then and first then you have to assemble the gearwheel.

At the moment i have to make some more.....So let me a little time...everybody gets the gearwheels....I have made only 9 for the first series.....

To see how it works and how it goes.....But now i can make some more.....

I have also dissasembled the switch, cause he hooks a little. I have clean the contacts and it have renew the contact spray. Not an ordinary spray.

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Today i bought in my electronic store in berlin some stuff i need.....I took the best they had there :yes:

And i saw that the little copperbrackets are a minimum bend. So i have give them with a microtang the right shape back and i have clean them too.....

Now the feeling is much better......

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Ghettoboom767

Member (SA)
Wow just wow!! I see a lot of happier Lasonic 931 owners out there!! Amazing!😎🎶🎼📻📻
 

Lasonic TRC-920

Moderator
baddboybill said:
Wow that is totally fantastic!! Where has this member been all these years.
When you were at your Lasonic ZENITH we talked so many times about trying to find a solution. And here it is!
 

Trommelmops

Member (SA)
Dear members and followers.....

Trommelmops has began to measure the whole switch.....Today i have made the plate with the shaft.....a special thread too.....M7x0.75 like on all of the switches.
Is a standard size thread.......but only for switches and potis.....

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caution

Member (SA)
Yeah Chris you can't glue or weld nylon, although JB Weld's plastic epoxy does okay with it. The stress this gear takes though, I doubt even that would work.
 
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