C107 Modification
Basic Information
C107 is a factory approved mod that is already installed in most Jupiter and Pegasus units. You should carefully check your rig before proceeding with this mod.
Information courtesy of Mark N8ME
This mod involves changing the [XMIT] ALC delay time so that the radio gets a chance to develop a slightly higher peak envelope power on voice peaks. The [XMIT] ALC is a little too aggressive and the earlier radios only would get to about 80 watts before it would kick in. This mod gets it to 100 watts. As described by Garry Green TT Factory Service, you replace 4.7 mf electrolytic capacitor C107 with a 2.2 mf electrolytic.
For C107, the first step would be to verify that there is actually a 4.7mF capacitor installed. TenTec has been updating Jupiters sent back for repair, so your Pegasus (Jupiter) may have already been modified.
To locate C107, remove the cover and place the Pegasus in front of you on its side with the power switch below the headphone jack. If you are looking at the front of the radio, the speaker will be to your left. On the PC board on the top side, locate the trim pot on the left side labelled "SWR". C107 is about an inch closer to the front of the radio. It's the only capacitor on the left side of the PC board. It's adjacent to a crystal.
Garry mentioned that the PC board is plated through, so the easiest way to replace the capacitor is to work the original one back and forth until the leads break and to solder the replacement on the top side of the PC board. This way, you don't have to remove the board from the Pegasus.
Photos courtesy of Mark N8ME
 click for full size |
BEFORE modification |
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AFTER modification |
Assistance
Don't hesitate to contact Ten-Tec Service (865-453-7172) or e-mail them at service@tentec.com if you are the least bit unsure about making this modification.