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HT-5 IPA bypass

F

fm-engineer

I have a customer that purchased a 300 watt digital exciter to replace a problematic THE-1 exciter and 200W IPA in a Harris HT-5. He wants me to make this change tomorrow. I should be able to drive the PA directly from the new exciter by removing the IPA, and I think there may be a directional coupler after the IPA that can be removed as well. Sorry, in a hotel, no manual until I get to the site tomorrow, and it has been a while since I bypassed an IPA in a HT rig. I can't recall if there are any drive interlocks, etc with removing directional coupler after the IPA. Am I on the right track here......? Thanks,

FM
 
Schematics are on the Harris website. Got a login?
http://ecustomer.broadcast.harris.com/

Only metering for IPA overloads are IPA current and IPA VSWR.
-0.3 V "Value typical for 500 watts IPA output"
Don't see any value for the IPA I overload.

From the book:
3.5.3 IPA BYPASS PROCEDURE
WARNING
ENSURE THAT ALL POWER IS REMOVED
FROM THE TRANSMITTER BEFORE PERFORMING
THE FOLLOWING STEPS. ALWAYS
USE A GROUNDING STICK TO ENSURE
THAT THERE ARE NO RESIDUAL
VOLTAGES PRESENT.
Bypass the IPA by completing the following steps:
a. Disconnect primary power.
b. Re-route the exciter RF Output cable from the
IPA RF Input, to the type N feedthru jack J1 on
the bottom of the PA cavity. A type N to BNC
adapter is provided.
c. Restore primary power and depress Plate ON
pushbutton.
d. Adjust the DIGIT™ Exciter output to 55 watts.
e. Retune the PA for maximum power output.
f. Adjust the PA screen voltage for maximum power
output.
 
Irronically the only failure I've had with our HT5 is the IPA power supply. A new pass transistor fixed that problem after I was able to get the part. Until then, I just took my personally-owned Nicom 300 watt amp and exciter and hooked it right in at the right power level. It worked perfectly... easy.
 
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