Has anyone been able to repair a KA power switch?

[sinnerboy]

My KA-701 Integrated Amp has the infamous broken blade on the power switch. The replacement switch seems unobtainable (I tried the APS TV5 switch, no go). Almost every example I see of this line (801, 701, 601) has the power switch broken off. It doesn't impact performance, it's just too noticeable. Has anyone found a way to repair the broken blade? JB Weld? I'm not terribly optimistic because it has such a small surface area and has stress on it when toggling on and off. I've thought about trying to fashion a sleeve for the blade to fit over the post to increase the surface area, just not sure how I would do that. And I would need to be able to remove the knob in order to remove the faceplate for maintenance / repairs. Anyway, wanted to see if anyone had tackled this problem.

 

[dlucy]

Is it a plastic part that could be 3D printed by a company like Shapeways.com?

 

[tarior]

No, it's steel.

OP, what does the rest of the switch look like?

 

[sinnerboy]

here is a side pic of the switch. You can see the blade typically breaks off at a second step-down. The blade that the knob presses onto is actually quite thin (hence the tendency to break). I've searched for the part number (TV-5 SDA3L) to no avail. If I were to take the switch apart, I suspect I would find the blade mounted on a rocker, held in by a small rivet. If that is the case, I could maybe remove the rivet and insert a new blade that has been filed down to the specs of the original. But without taking the switch apart, that is just speculation. My latest idea to think about is to mount the knob permanently onto a shaft that would slide over the broken base, like a sleeve. I bought a knob of eBay as a replacement, but it came without the plastic insert that holds it to the blade. It could be that having a knob like that will make this idea work (more flexibility into what I mount it to). The sleeve would have to be fairly tight tolerance in order for the toggle not to have slop in it, while being able to remove the knob / sleeve part in order to remove the faceplate. Still thinking about how I would fabricate that sleeve, finding a metal that is thin enough to shape yet strong enough to hold the base of the switch tight. I did read that someone butt welded a new tip onto the blade, but that is beyond my capabilities and equipment! Hmm, just thinking as I write, I may try to use a wire connector (spade type) as the sleeve (massaged a bit). If I can get the size right, that may work.

 

[tarior]

The typical repair is to steal the blade out of a function switch of some sort, one that matches, and graft it in. AFAIK, no one is making those thin bladed toggle switches any more.

 

[sinnerboy]

Yeah, I saw that write up, hence why I'm looking for an easier solution....

 

[tarior]

Unless you can find another switch with an identical bat, you may not have much choice.

 

[gort69]

How crucial are the wings on the toggle? If you could make it work w/o them, seems that an alps switch with a longer toggle with the same screw spacing could work.

 

[sinnerboy]

I read that the Ka 9100 toggle could be made to fit, i cant find one of those either.

 

[gort69]

They show up from time to time. KA-6100,7100, 8100 & 9100 power switches are all interchangeable.

 

[fernarias]

Yep, the 1980 separates had this fault. I have several 701s, cassette player and tuner with the same issue (I have one 701 that's perfect). These switches were made to break instead of bend (less calls to Kenwood customer service, probably, since you clearly broke a piece of steal). If I get a garage again, I will try to weld the end. So I think welding would be the best solution.

 

[tarior]

I once saw a Marantz slider balance that had a very interesting repair. The stub of the original and the bat of the replacement were ground on a taper like the two ends of a bandsaw blade, and then had two pins put through them, and then soldered. It was a pretty solid repair and who ever did it had some skills.

 

[gort69]

If I get a garage again, I will try to weld the end.

I tried it twice with a MIG welder - I was one for two. The first was successful, the second resulted in a melted blob

 

[fernarias]

I tried it twice with a MIG welder - I was one for two. The first was successful, the second resulted in a melted blob

This gives me hope.

 

[Starquest]

JB Weld the thing back together and use a power strip to turn it on and off.

 

[sinnerboy]

Thanks for all the replies. I'm going to try this. I'm going to square off the stub. I fabricated a new bat from some split copper tubing. I'm going to epoxy (or JB Weld) the bat to the switch arm, wrap it in some thin copper sheeting i use to line guitar cavities, and see if that holds. The sheets are thin enough to pass thru the plastic collar if i wrap it tight enough. Obviously I'll be generous with the epoxy. If it still feels weak, I'll follow Starquest's suggestion!