[TenTec] 9420 P/S Problem....Need Help

[Bob Good]

Greetings “Tentechnical” Friends........  I have a problem with my old “reliable” OmniVI > Hercules II (with 9420) > 238 station.  I have concluded the problem is with the 9420.  Omni straight through is fine.  Disconnect the 9420 and run the Herc off a battery, works fine.  Here is the symptom:  While bringing the power up to about 200 watts output into a dummy load with a 1.2:1 swr,  a relay starts to chatter in the power supply.  The pilot lamp in the Herc (now a led) almost extinguishes with each pulse of the relay.  Monitoring the Voltage, the Herc Meter indicates it just wiggles at about 14 volts indicated.  The RF output appears to drop out with each relay pulse and the current meter wildly fluctuates.  I have all the manuals by Ten Tec and have looked at the diagrams.  I have opened the top of the unit and nothing is burned.  Harness plugs appear to be seated.  I am assuming the problems lies with the circuitry on the P/S controller board involving either K-3 or K-4.  I have not tried to go further by hooking the 9420 back up to the Herc or disassembling the unit.  I have not yet checked voltages inside.  Of course, it is running on “220” vac.  I am hoping some of you perhaps have had the same problem and can help me step through the repair.  If you have free long distance, I am available at 912-863-5767.  All my info on QRZ is current.  Thanks for reading and please spread the word.  Regards,  Bob K4BG