[Kenwood] TS-180S Mystery and TS-120S ALC Meter

[Steve]

At 03:18 PM 5/22/2010, w9jdh at netzero.net wrote:
>While I am typing, I may as well ask about another problem. I have a 
>very good TS-120S
>that has a problem with the transmit metering. It will not indicate 
>the Ic, or the ALC. I
>read where there was a problem with the pushbutton switch on the 
>front panel. I have
>cleaned the switch, with no results, and it shows OK when I check it 
>with a VOM. It
>started out as an intermittent problem, but now it doesn't work at all.

Very common on the TS-120S. The problem is, indeed, the switch. To 
verify that, you can remove the front panel then if you're still 
young and dexterious enough to find the appropriate PC board traces 
and pads connected to the switch, solder short wires to the pads. Put 
it back together far enough to be able to turn it back on. Note that 
when you short the wire ends together to simulate the switch being in 
ALC position, that the meter reads properly. It's a very vexing and 
confusing problem.

I theorize that it's because the current through the switch contacts 
is so small that the least little bit of corrosion doesn't allow 
sufficient current through the contacts to activate the meter; but 
most digital VOMs will pass a mil or more current and that usually 
makes it through the contacts.

I once tried installing a tiny relay to take the place of the switch 
contacts, but screwed up somewhere and it didn't work right. I gave 
up after several hours and removed the relay.

I've even removed and disassembled the switch to clean the contacts 
manually, but to no avail.

Steve, K0XP