I added a relay to both my KR-6600 and KR-7600 to prolong the lives of the power switches. The idea for this comes from member EchoWars, who posted the workaround for the KR-9600 power switch and credit goes to him. I just adapted the concept and the parts list to these two smaller receivers. EchoWars' writeup and the parts list can be found here: http://www.audiokarma.org/forums/showthread.php?t=464045&highlight=workaround
These photos are from the KR-7600. The KR-6600 is virtually identical as far as this modification goes.
In order to do it this way, you need to remove the top , bottom and left side covers and the faceplate, and it will look like this:
The first thing I did was install the fuse holder. This is where there is a slight difference between the 6600 and the 7600. The 7600 seems to have a taller heat sink, and when I tried to mount it like I did on the 6600 it was too tall and hit the top cover. So I went to Radio Shack and bought their fuse holder p/n 270-739 and used it http://www.radioshack.com/product/index.jsp?productId=2062257 -see picture below. I just removed one of the screws holding the station pointer base onto the heatsink and installed the fuse holder using the same screw. For the power to the new fuse, I used the post just to the right of the main fuse which comes directly from one AC leg of the power cord.. (yellow wire) If the main fuse blows it makes this relay circuit dead also.
Here is the fuse holder I installed on the KR-6600. Same one EchoWars listed. I used the same screw to locate it, but used a 3/4" x 1/2" angle bracket. (hardware store item, Stanley)
I soldered another wire to the other side of the fuse holder - this wire will go to one terminal on the power switch.
There aren't a lot of options for mounting the relay on these. I considered mounting it on the side rail (see photo) but would have had to move a bunch of stuff out of the way in order to drill holes...
...so I opted to mount it to the rear plastic panel. This required drilling two 1/8" holes and using 6-32 machine screws and nuts. The only thing that shows from the rear are two phillips screw heads - I forgot to take a photo.
Here is the relay mounted. Also installed is a (yellow) wire to one side of the relay coil coming from the other AC leg (soldered to post)
A wire runs from the remaining relay coil terminal to the remaining power switch terminal.
So to recap (haha) I did the wiring for the relay coil as follows: Fused AC power cord lead > new fuse > power switch > one relay coil terminal and from the other relay coil terminal straight to the unfused AC leg. I hemmed and hawed as to where to put the fuse in the circuit and kind of decided on my own that it really doesn't matter since these old things didn't use a polarized plug.
Next I cut the original wires to the power switch (gray and white) and moved them over toward the new relay to be dealt with later
I then removed the power switch from the chassis
I removed the original safety capacitor and desoldered it, then soldered on the two new power switch wires along with the new safety capacitor that EchoWars prescribed then reinstalled it in the chassis.
Next I went back to the original gray & white power switch wires. I crimped and soldered them to spade terminals along with the arc snubber EW specified, heat shrinked them (heatshrank?) and installed them in the new relay.
Then tidied things up a bit with some zipties, tested it and reinstalled the covers.
These photos are from the KR-7600. The KR-6600 is virtually identical as far as this modification goes.
In order to do it this way, you need to remove the top , bottom and left side covers and the faceplate, and it will look like this:
The first thing I did was install the fuse holder. This is where there is a slight difference between the 6600 and the 7600. The 7600 seems to have a taller heat sink, and when I tried to mount it like I did on the 6600 it was too tall and hit the top cover. So I went to Radio Shack and bought their fuse holder p/n 270-739 and used it http://www.radioshack.com/product/index.jsp?productId=2062257 -see picture below. I just removed one of the screws holding the station pointer base onto the heatsink and installed the fuse holder using the same screw. For the power to the new fuse, I used the post just to the right of the main fuse which comes directly from one AC leg of the power cord.. (yellow wire) If the main fuse blows it makes this relay circuit dead also.
Here is the fuse holder I installed on the KR-6600. Same one EchoWars listed. I used the same screw to locate it, but used a 3/4" x 1/2" angle bracket. (hardware store item, Stanley)
I soldered another wire to the other side of the fuse holder - this wire will go to one terminal on the power switch.
There aren't a lot of options for mounting the relay on these. I considered mounting it on the side rail (see photo) but would have had to move a bunch of stuff out of the way in order to drill holes...
...so I opted to mount it to the rear plastic panel. This required drilling two 1/8" holes and using 6-32 machine screws and nuts. The only thing that shows from the rear are two phillips screw heads - I forgot to take a photo.
Here is the relay mounted. Also installed is a (yellow) wire to one side of the relay coil coming from the other AC leg (soldered to post)
A wire runs from the remaining relay coil terminal to the remaining power switch terminal.
So to recap (haha) I did the wiring for the relay coil as follows: Fused AC power cord lead > new fuse > power switch > one relay coil terminal and from the other relay coil terminal straight to the unfused AC leg. I hemmed and hawed as to where to put the fuse in the circuit and kind of decided on my own that it really doesn't matter since these old things didn't use a polarized plug.
Next I cut the original wires to the power switch (gray and white) and moved them over toward the new relay to be dealt with later
I then removed the power switch from the chassis
I removed the original safety capacitor and desoldered it, then soldered on the two new power switch wires along with the new safety capacitor that EchoWars prescribed then reinstalled it in the chassis.
Next I went back to the original gray & white power switch wires. I crimped and soldered them to spade terminals along with the arc snubber EW specified, heat shrinked them (heatshrank?) and installed them in the new relay.
Then tidied things up a bit with some zipties, tested it and reinstalled the covers.
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