The best way to fine tune the GI's MDR pots I FIND is to first
1. assuming using sweep equip, have your reference file from other amp and then ,,
As you normally would balance the amp (in manual) pad and eq your input side to your design spec and then , stick your probe in the output, crank your amp all the way up to make sure you are getting the proper gain, (which should be I beleive 32 Db on GI).. you want to make sure your hybrids are giving you proper gain.
Then back off however many db you are supposed to by the ambient temperature chart. . Re-EQ if necessary for your designed Tilt, and re-pad outputs or interstage if necessary also.
Then go over to sweep and put the meter in 1 - 2 db per division and sweep against the reference., . HOPE that the people that have worked on this amp prior to you have had experience with the board, and haven't randomly tweaked dials. The worst ones to mess with if you have no experience are the ones that have a little epoxy in them, and look like small phillips screws..
I believe the difference in the pots is some are pots and others are varistors,..one adjusting level the other adjusting freq range.
Just pay attention closeely to what you are affecting as you tweak the dials.. some of the pots are sensitive and you will want to tweak and remove the tweaker off the pot and let your sweep trace "settle".. Esp bad with metal "diddle sticks". Use ceramic if possible.
Sometimes you will find that the board being offset by other technician will have caused him to use the wrong input eq .. For example, one pot you will see affects from about 55-65 MHZ in a real sharp hump or valley in the low end. you almost have to move your marker away from the low end to make sure its not there sometimes, REAL SHARP.. If this is set wrong, get it to where it needs to be to make the trace flatter.., and after adjusting a few other pots, will find that you must now RE=EQ the amp... After doing so, amd more SWEEP MDR tweaking.. you'll start seing awesome Peak to Valleys deep into your cascade.
Everything there is to the best of my knowledge, and from info picked up from the Motorola guy that came show us things, as well as own experience.. If anything is incorrect or anyone have better ideas please lemme know.
By the way don't forget to put the amp in Drive Unit mode if applicable and fine tune ADU or TDU.
Re: Pots on GI gear
Member #: 15503
Registered: 1996-2001
Posted:
26
Name:
Kevin
Occupation:
Equipment refurbishing
Location:
Louisiana
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