Furman PS-8 Schematic needed (or capacitor part identified)

[rocknroller]

Made a mistake working on a amp and blew the power strip fuse (10 amp) it was connected to. Turns out it also blew the 20 amp house fuse for that circuit as well which had me scratching my head. Kept trying to reset the house fuse and kept popping. After searching the rooms, found on that same circuit (different room), I had a Furman PS-8 Power sequencer and it was blowing the house fuse.

Opened up and found a blown disc capacitor? Not sure it's really a capacitor, but looks like a huge disc and is connected to the incoming power. See pic. Not sure how it got blown but it and I can't identify what it is/was and can't find a schematic anywhere either. I did a quick check on the diodes and other components nearby and everything seems ok and it's just this part that blew up. If it is the same as the other two beside it, I may want to replace those as well I suppose.

[rocknroller]

The two that are on each side of the blown one read
S20K
130
914

I find a S20K130 varistor when I search and looks to the be same thing, though no way for me to know 100% the blow one is the same thing with a schematic confirmation. I don't know what the "914" stand for, perhaps just a manufacturer location code? not relevant?

[Enzo]

914 is a date code.

yes, those are varistors. What you looked up is likely just what you need.

[Steve L]

S is a model designation used by Epcos or Siemens, the manufacturer of the MOV. (Metal-Oxide Varistor)
20 is the MOV disc size. (20mm)
130 is the AC voltage at which the MOV will start conducting when exposed to an over-voltage.

A 130VAC MOV is not often used these days. What may have happened is that the devices actually did their job and protected the connected circuitry.
Or, what could have happened is that the line voltage was higher then normal for an extended period of time. A 130V MOV can withstand 130V and even more for short periods of time, but it will start to degrade.
The eventual failure mode is that the MOV will eventually short and then get blown open by the current that will follow through it.

Furman should have placed a properly rated thermal fuse next to the MOVs to prevent the damage you see, and in many cases, far worse damage.
Nominal AC line voltage for electrical design purposes in the US is 120VAC, +10%, -15%. (102 to 132VAC)

Clean up the board, getting rid of as much as the MOV residue as possible and replace the MOVs with devices rated for 140 or 150VAC instead of 130VAC.
The higher voltage MOVs will limit voltage at a higher level, however they still give good surge protection and will not likely cause what you see again.
You can find 20mm or larger MOVs at the usual sources such as Digi-Key, Mouser, etc. Be sure you select the voltage rating for AC, they are also rated for DC as well.

Steve

[Jazz P Bass]

It appears that the MOV failed short, across the lines.

[g1]

Furman should have placed a properly rated thermal fuse next to the MOVs to prevent the damage you see, and in many cases, far worse damage.
Nominal AC line voltage for electrical design purposes in the US is 120VAC, +10%, -15%. (102 to 132VAC)

Clean up the board, getting rid of as much as the MOV residue as possible and replace the MOVs with devices rated for 140 or 150VAC instead of 130VAC.

It looks to me like there may have been another component above the diodes there where there is an oval shaped outline in the char.
(edit: I guess if this were some type of fusible part it should not be blowing the house breaker)
It should be more visible if he cleans up the area (isopropanol and swap should do) and posts another picture.

[Enzo]

You could be right, but I don't see a vestige of silk screen or a hole or tracery. I look there and see where the flame from the failing center MOV played right on the board. That oval is a crater. Just a thought.

[g1]

Looking at it from that perspective makes sense (flame out emanating from the MOV).
I just saw the little circle where I've marked with the arrow and thought it may be where a lead once was.
Cleaning should clarify.