[Test-Equipment] Need help repairing IFR1600- from Korea

[Yongsurk Lee, HL1FB]

Hello;
     I am repairing an IFR1600 made in 1995.
I bought used and have been using it for the last 15 years with no problem.
Recently it suddenly stopped functioning with some burning smell.
I guessed it must be power supply problem, probably caused by shorted
tantalium capacitor somewhere in one of the board. I saw similar problems
while repairing ham and test equipments.
I found the IFR1600 power supply's +15VDC line is shorted at the power
supply side(only 6 ohms to chassis). And +15VDC input pin(pin 5A,B) of the
Receiver module showed only 28 ohms.
Is this 28 ohm normal? I have a maintenance manual with block diagram, no
schematics.

Could someone answer?