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Maxtrac low-band repair

Posted: Sat Mar 22, 2008 3:40 pm
by John
I have a low band Maxtrac with a transmit problem. It will transmit fine in the TX Alignment screen of the RSS but when you operate in normal mode and transmit the power is initially OK but immediately drops to 5 watts. Has anyone seen this problem before? Anyone have any suggestions?

Re: Maxtrac low-band repair

Posted: Sat Mar 22, 2008 7:08 pm
by Max-trac
Double check you are on a frequency that is in the correct bandsplit for the RF and PA board.
Try several different frequencies accross the bandsplit.
Turn the transmitt power down to 50 watts and try again.
Try a full alignment (select replace logic board).
There could be something wrong in the current sensing PA feedback. You could put a manual power control pot in it.

Re: Maxtrac low-band repair

Posted: Sat Mar 22, 2008 10:29 pm
by kc7gr
This is a common symptom with radios that have been reprogrammed (but perhaps not properly modified) to handle the 6m band.

What I usually end up doing is bypassing the power control circuitry, and installing a simple mod (three fixed resistors and a trimpot) that allows setting the power out manually. I've done so to numerous 900MHz radios, as well as a couple I've put on 6, and had no problems at all with it.

The mod for doing so was created by Robert Meister, and may be found at this link.

http://www.repeater-builder.com/maxtrac ... ntrol.html

Happy tweaking.

Re: Maxtrac low-band repair

Posted: Tue Mar 25, 2008 3:27 pm
by Will
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