The HP 8647A is an excellent signal generator with a lousy power supply. Here is how to use an Artesyn LPT-103-M and an XP-Power EML30US36 to replace the dead original. CAREFULLY use a jeweler's screwdriver & magnifying glass to set the XP-Power to 38 volts. Remove the original and put the new ones in its place with standoff insulators. A slice of ballpoint-pen barrel will do.
ALL THE USUAL DISCLAIMERS: I'm not making any money on this. I won't be responsible if you blow up your PSUs nor your signal generator. I'm trusting you to be a skilled Electronics Tech. I won't be responsible if you electrocute yourself. I won't be responsible if you do a swandive into a raincheck.