KR-9600 power regulator mod question

Hello All,

I realize this mod has been covered already in several posts, I just cant seem to find the actual how to and where to solder descriptions. My question is on adding this 25W 75ohm resistor to my 9600. The amp is usually always on and it gets very hot and i've already had to resolder the 2 resistors back in place. I want to add this resistor that I read about in these forums to cool things down..

The first pic is somebody's pic I got off here, but my question is wiring.. i'm assuming that one lead goes to one side where the resistors were in the pic and the other lead (orange wire in pic) goes back to the other side of the resistor. From the pic, it looks like the wire thats on the other side of the pic is black as the picture is cut off?, and it looks like an orange wire goes back to the main board where the other resistors used to be.

My regulator board looks slightly diff from this board in the pic. Is there anything specific I need to do or look out for when doing this mod? I'm kinda just asking for advice on the wiring for this and the original pic, doesnt really show the wire routes..

If its possible can somebody post a clearer pic of this mod for me, it would help me out. Its greatly appreciated. Thanks alot!

That's my photo. It's pretty basic wiring. There's a wire coming to a pin on the Power Supply B board that then has a trace going to the two paralleled 120 Ohm 2 watt resistors (the ones covered in tubing). Then on the other side of those same two resistors there will be another board trace that connects them to the collector or Qr1 (I believe its the right mounted tranny in your photo, but follow the trace to be sure). Just remove the two 120 ohm resistors first and then have the 75ohm 25 watt resistor between the incoming wire and the collector of Qr1 in whatever fashion suits you. Of course you need to mount the resistor to the heatsink panel to keep it cool.

I believe the way I wired mine I used a second wire beneath the board that can't be seen that goes from the pin to the pad where the collector leg is. I'm not sure why I did it that way, but I was attempting keep it stock looking.

Thanks I will try that. So in my pic, I can just solder one lead of the 75ohm to that pin that has the white red stripe wire (incoming)and then solder the other side over to that qr1? I was trying to figure out how on your board you have an extra pin near the lower resistors and some pins look like their missing on the upper side. And was trying to figure out how you had an orange wire coming through your board but there was no orange wire going to that 75ohm resistor. Lol, was confused. Think I see what you did now. Appreciate the reply. You did a great job on your amp. Looks good.

Best advice is to follow the traces, you can't go wrong with that. I wouldn't want to speculate about what pin/wire color anything is what without being able to see the foil side of that board myself.

I got it in, I followed the traces and was fairly easy and it works. I ran it for about 15/20mins or so and noticed the heatsinks and remaining 2 resistors are heating up fairly good still. The aluminum resistor was cool.

I'm confident that it was done right. I followed the traces and inserted this aluminum resistor with one lead soldered directly to the board with the trace going back to the transistor. I removed the red/white wire that was on pin 3 and soldered it to the wire going to the other side of the aluminum resistor and shrink tubed it.

I may just have to replace Rr3 & Rr4 with aluminum's like Tarior did. Does Qr1 and Qr2 normally run hot to where the heat sinks are very hot? Doing this mod didn't require an "automatic" change of Qr1 and Qr2. I read your post on the restoration info but didnt see anything about replacing Qr1 and Qr2 if you did the mod, basically keeping it stock with new thermal compound. But I know this board is a notorious heat concern.

So I just wanted to make sure this was normal behavior and this mod didn't cause anything bad to happen? Lol, i'm a little over paranoid I guess. I prob should have taken notice before I did it to see what is normal.

Thanks again.

If you'll notice the board is discolored worst at the hottest spot and that is where the 120 ohm resistors used to be. Kenwood knew it was going to get toasty there and this is surely the reason for two large resistors in parallel rather than just one 60 ohm. The increased surface area was being used for dissipation. It surely wasn't a cost savings.

I'd say you've gone a long way to improve things. While the heatsinks will put off heat, that is there intended purpose and so long as you didn't apply too much compound to Qr1/2 (just a thin layer is what works best ) that should help shed heat better than the 35 year old, dried out, powder residue you found there. It's not going to run cool on that board, but as I recall, it is "blister your hand" hot before any changes are made. Nice work.

If you haven't already, take Q1 and Q2 loose from the heatsink and apply fresh heatsink grease after cleaning the old stuff off.