Audio Output Modification
As heard on Ten-Tec 7.251 net, May 18th, 2003The modification consists of the removal of surface-mount resistor R37 on the logic board. This circuitry is on page 4-17 of the Jupiter manual, schematic 4-21.
NOTE: This modification is not required on newer Jupiter/Pegasus radios, as the resistor has been omitted from new production rigs. (Anyone know the date or serial number range at which they began omitting the resistor? Help me out.)
From Jerry KO4CH:
The resistor we were discussing is resistor R37 on the logic board located on the bottom right front side of radio as you have the radio turned upside down facing you. It comes off the U-12 audio IC that is located on the extreme right side mounted vertically on the board. It is a surface mount resistor and very small of course.
I found the easiest way to remove it was to take a small pair of cutters and clip it in the middle (see pictures below).
It improved the audio response and was able to copy an S-2 signal on 10 mtrs with the audio set at 35% It also improved audio on weak signals on the other bands. It appears to be a bleeder resistor going to ground. It does work and not hard to do.
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A view of the schematic, reproduced from the Ten-Tec Jupiter manual, showing the location of R37. |
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A view of the board layout, reproduced from the Ten-Tec Jupiter manual, showing the location of R37. |
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The Jupiter case, open to show the relative locations of the board and R37. Photo courtesy Jerry KO4CH. |
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R37 before the modification. Photo courtesy Jerry KO4CH. |
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R37 after the modification. Photo courtesy Jerry KO4CH. |