KT-7500 Power switch

vin45

vin45

New Member
I have a KT-7500 and have had it sitting in my study for about 7 years. It was part of a deal to buy a Model 600. Now I've sold my Model 600 (not working) to an AK subscriber who is bringing it back to life. The replacement is a nice KA-7300 that will be delivered on Wednesday. My thought was to sell the KT-7500, since FM reception here in Davis, CA, is bad, but having a new bite by the vintage audio bug, I thought I'd try to fire it up. First step, power it on! But the power switch does not work. It feels stiff. I opened the case, and I don't think it had ever been opened before-a very clean case without a scratch, very clean interior, unscarred phillips heads on the case screws. Does not seem to me it has been damaged, although I suppose the switches can be bumped externally without much evidence....

Can anyone tell me whether it is likely to respond to deoxit or some other cleaner, or if it is likely to need a new switch? Or suggest another next step?

Thanks!



KT-7500.1.JPG KT-7500.2.JPG
 
Register to hide this ad
Generally, it is not advisable to use any cleaners on power switches unless they are disassembled and open for inspection. Cleaner residue and any contaminants moved around by cleaners can contribute to further switch contact arcing and failure.

It may be helpful to measure voltages at the switch just to verify that the switch is a problem, instead of a fuse, connection, cord, or something else.
 
Watthour said:
Generally, it is not advisable to use any cleaners on power switches unless they are disassembled and open for inspection. Cleaner residue and any contaminants moved around by cleaners can contribute to further switch contact arcing and failure.

It may be helpful to measure voltages at the switch just to verify that the switch is a problem, instead of a fuse, connection, cord, or something else.
Click to expand...

Thanks again. Is the switch shown familiar to you? I have never disassembled and opened such a switch for inspection, and maybe there is a source of instruction for this.
P
 
Watthour said:
It appears to be a Noble switch, but I have never serviced that specific type. It also appears that the phenolic switch body is held in place by tabs bent over the shell.

A similar Noble switch design is detailed here:

https://www.audiokarma.org/forums/i...an-rebuild-him-we-have-the-technology.372256/
Click to expand...

Thanks for you advice. The switch came out easily. It looked very clean, but there is a piston in the center that was frozen. I confess I put a very small drop of Deoxit on the piston and it instantly was free. The reassembly was only a bit tricky since the switch mechanism works with two delicate symmetrically opposed springs that capture the internal end of the piston...but it is back together and operating well! It would have been more difficult to disassemble the piston segment of the switch to clean it without Deoxit. Some other lubricant might have worked adequately, but this worked. At first only the pilot power light came on, but then the meter and scale lights came on and are working. I'm posting photos in "Show me your Kenwood."

Thanks again!
 
You must log in or register to reply here.
Back
Top Bottom