HP 75000 E1300A cleaning and repair -- feasibilty of fixing Schaffner input?

[jbachmeyer]

Long time off-and-on lurker; first-time poster.

I recently scored an HP 75000 off eBay for ~$50 and it even worked when I plugged it in!  Then I took the cover off and found it full of 20 years worth of dust. 

While pulling it apart for cleaning, I checked the boards and found the internal digital meter has some RIFA capacitors near its input section -- and they are bad, with cases already cracking.  I waffled a bit about actually pulling the system completely apart, then noticed the power inlet module, took it loose, pulled it out a few inches to reveal ... "Schaffner" on the label on the bottom, complete with a little hole in the metal shell just above what looks like a little tarry bead inside the filter.

My questions:

1.  The power wiring inside the unit seems odd to me, with a bunch of wires not connected.  The power supply is marked LR55465 and ETU-4MS23UPZ.  Can anyone here tell me how this is supposed to be wired?

2.  Is it feasible to "defuse" the Schaffner by replacing the exploding capacitors before they go boom?  Otherwise, any suggestions on how to replace it?  The voltage selection switches appear to actually be important, but only the 115V setting appears to be connected, thus my other question.

[Kubota]

The "Schaffner" is both a power line filter and a voltage selection switch.   If it is damaged, then you should be replaced it with a new or similar one.    The power supply has a wire on the side (white) and a terminal for selecting the voltage (120 or 220V AC).   The 75000 B chassis has the white wire running to the "Schaffner switch and returning the (100V-120V terminal on the board) .   If you are in the USA and use 120 volts then you need to ensure that the white wire is shorted to the 120 volt terminal next to the silkscreen 100-120V.    This short is normally done with the selection switch on the Shaffer when selecting 115Volts on the exterior of the chassis at the power entry and fuses.   You can jumper the white wire directly to the terminal labled "110V -120V" and this will work but if someone plugs the unit into 220V the power supply will be damaged.   It is better to use the "Shaftner " exterior switch to make this selection.
   If the power supply is functional then you may be better off using it as is.   However,  If you want to extend the life you can replace the on board electrolytic capacitor.

[Andy Watson]

... "Schaffner" on the label on the bottom, complete with a little hole in the metal shell just above what looks like a little tarry bead inside the filter.

  Does it stink? Does the smell get right to back of your throat and remain there for several days? If so, it may be too late to "defuse" it.

2.  Is it feasible to "defuse" the Schaffner by replacing the exploding capacitors before they go boom?  Otherwise, any suggestions on how to replace it?  The voltage selection switches appear to actually be important, but only the 115V setting appears to be connected, thus my other question.

Yes - it is possible, but probably not practical to replace the capacitors. The Schaffner units are potted in a resin. I have replaced the capacitors in one Schaffner filter - this convinced me that it was worth paying the extra expense to purchase a new filter when a second unit failed. Search your favourite suppliers with the Schaffner part number - many of these parts are still available.
If the tar-y resin has dribbled, it can be removed with isopropal alcohol and patience.