# What Fuse Is The Correct Replacement?

I got a HP Universal Counter on my desk, but it did not turn on, so I checked the fuse. The original fuse reads

SOCSD4 D250V150mA


What kind of fuse could I use to replace it?

It's 32mm long, 5mm in diameter. Two metal caps on both ends, inside there's a white nylon or ceramic string with I ~.1mm copper string helixed around it.

• Not even a picture, drawing, or any kind of measurement!? – Olin Lathrop Feb 23 '12 at 17:08
• Seems like 150 mA and 250 V. A better answer will require more information. – Olin Lathrop Feb 23 '12 at 17:29
• Some additional basic information we need: Length, diameter, a picture. Googling, it seems like SOCSD4 is a common type/marking. google.com/… – Chris Laplante Feb 23 '12 at 17:58
• What model is the counter. HP test equipment division spun off to Agilent long ago but they may still have relevant documentation on their website, for example home.agilent.com/agilent/… – Matt B. Feb 23 '12 at 20:49

Actually, I think I found it. SOC appears to be the company, leaving SD4 as the product name. Take a look: http://www.socfuse.com/products/pdf/P59_E.pdf

It's a time delay fuse - the wire on the inside will be a little twisty coil as opposed to a straight piece of wire. The voltage and amperage rating fall within the range on the data sheet, so I'm 99% certain that I've found the right fuse.

I'm no expert, but I've done a search on Mouser and here are possible replacements. Before purchasing, please let someone who knows what they are doing, like Olin or Russell, confirm or deny that the fuses I've found will work.

The parameters I set were 250 volts, 150 mA, Time delay, "Cartridge" style, and the dimensions.

Note: The actual dimensions of the fuse are 31.8 mm Length and 6.35 mm Diameter, which is the same as 1.252 inches L and 0.25 inches D. The search I performed on Mouser allowed fuses that were 1.25 inches L and 0.25 inches D as well, since it gave me more results. I'm not sure what kind of fuse clips you are using, so be aware that they might not fit perfectly, or at all.

Also, there were three "Midget" fuses from LittleFuse in the results that only specified the length as 38.1 mm. I don't know what the width is, so I'd advise against them, especially with a non-stocked lead time of 17 weeks.

Be sure to conduct a similar search on Digi-Key as well. I just tend to gravitate towards Mouser for some reason. But be sure to select time-delay fuse!