Maxtrac Question

sparky2842 · Post by **sparky2842** » Wed Nov 22, 2006 3:57 pm

I was wondering what the pot on the back of the radio on the heat sink does? Curiosity killed the cat, so before I touch it and regret it, Let me know... Also is there a way to modify for variable power for low and high? The sink gets pretty hot while talking on the ham bands...

bellersley · Post by **bellersley** » Wed Nov 22, 2006 4:09 pm

That's not a pot, it's part of the power amplifier transistor.

At least, that's what the service manual leads one to believe. You adjust output power through the tuning/service menu.

sparky2842 · Post by **sparky2842** » Wed Nov 22, 2006 4:16 pm

Thank you... Ok i wont mess with the screw on the back. I was wondering if I could modify the radio with a switch with resistors on the tx board so I could change the tx power in the field without a computer..

PETNRDX · Post by **PETNRDX** » Wed Nov 22, 2006 11:43 pm

I suppose its possible to "modify the modification"...
There is a modificaton listed on the Repeater-Builder webpage to make power output control by a trim pot inside the radio.
The intent is to use this mod when using the radio outside of its design band where the radios tend to run "wide open" trying to put out something like 60 watts.
But, I must mention that if you try to run the Maxtracs much below appx half rated power, they get just as hot, but might put out spurs.
So, since the circuits in the radio were not designed for a low power setting, you might not have much luck.
I have had best experience with just setting the power out for about 2/3s or 3/4 rated power, and leave it at that.
That is one drawback to Maxtracs/Radius/GM300's they get HOT!.

sparky2842 · Post by **sparky2842** » Thu Nov 23, 2006 1:31 am

I'm not worried about the high power just the heat. I got 2 fans for the back today. I just gotta figure out how to mount them on the fins..

Doug · Post by **Doug** » Thu Nov 23, 2006 5:51 am

As strange as this may sound I've used aluminum anchors for hanging pictures on drywall. They expand just enough between the heat sinks to keep it snug.
Doug

kb0nly · Post by **kb0nly** » Thu Nov 23, 2006 7:33 am

Or make a plate to put two small fans on and use the mounting hole in the center of the heatsink. That hole is there for the extended mounting brackets that use a self tapping bolt to secure the back end to the bracket.

phrawg · Post by **phrawg** » Thu Nov 23, 2006 7:58 am

and remember to place the fan so the airflow draws ait through
the fins, not tries to push it through. Cooling is MUCH more
efficient that way. Phrawg