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Power Supply PCB Microfuses for H/P 8656A

 

I`ve had a look for these [Littelfuse 027001.H , 027004.H , 027004.H.....1A, 4A, and 5A respectively] on the internet, including the manufacturer, and their local agent, here, and others. I`m looking for perhaps a couple each,? to restore the 8656A to origonal. [A couple of the fuses that plug onto the PSU section had blown at some time , and had been replaced with fine TC wire wrapped arround the pins - a purists nightmare, and an unsafe practice!]
Can anybody in the group please help me with this?

BTW; What goes wrong with an 8656A after 27 years and 5 months use and abuse ? I hear you? ?ask : The usual selection of scratches, and bumps [these were cleaned with gasoline, as this didn`t dissolve anything, and got the deep grime out]. The fan didn`t need replacing, and is dated `81.Some of the plastic locating pegs had broken off the side plastic panels.? The instrument had been operated in a damp environment, so there was white corrosion inside the fan compartment. One display driver chip had failed, and was replaced - it was a common variety, available locally.The only repairs in 27 years appear to be a replacement 5Volt rail smoothing capacitor, and a large Tantalum in the supply to the attenuator, and the attenuator PSU crobar SCR. This only leaves? the PSU fuses to be looked at. Hoping this is of interest....................Don C. ZL4GX?
 

Hi Don -?

I gather from your call sign that you're in New Zealand.? I'm not sure if Digi Key will be much use (seems to me guys on the eevblog from Aus and NZ mention using them, so maybe...), but they carry what I think are the correct fuses, and have stock.

I downloaded the PDF manual from Keysight and they appear to be Littelfuse Micro 273 series fuses - the manual lists them as mfg p/n 273001, 004 and 005 which I believe correspond to Littelfuse part numbers 0273001.H, etc. (I suspect that you already know this, but just in case...); DK part numbers for these are F868-ND, F872-ND and F873-ND respectively for the 1, 4 and 5A devices.? They're $5.85 US each, and they currently show north of 1000 of each in stock.

Take a look and see if these are the correct fuses.

I hope that this helps you.

-Pat


On Tue, Oct 02, 2018 at 03:52 AM, donald collie wrote:

I`ve had a look for these [Littelfuse 027001.H , 027004.H , 027004.H.....1A, 4A, and 5A respectively] on the internet, including the manufacturer, and their local agent, here, and others. I`m looking for perhaps a couple each,? to restore the 8656A to origonal. [A couple of the fuses that plug onto the PSU section had blown at some time , and had been replaced with fine TC wire wrapped arround the pins - a purists nightmare, and an unsafe practice!]
Can anybody in the group please help me with this?

BTW; What goes wrong with an 8656A after 27 years and 5 months use and abuse ? I hear you? ?ask : The usual selection of scratches, and bumps [these were cleaned with gasoline, as this didn`t dissolve anything, and got the deep grime out]. The fan didn`t need replacing, and is dated `81.Some of the plastic locating pegs had broken off the side plastic panels.? The instrument had been operated in a damp environment, so there was white corrosion inside the fan compartment. One display driver chip had failed, and was replaced - it was a common variety, available locally.The only repairs in 27 years appear to be a replacement 5Volt rail smoothing capacitor, and a large Tantalum in the supply to the attenuator, and the attenuator PSU crobar SCR. This only leaves? the PSU fuses to be looked at. Hoping this is of interest....................Don C. ZL4GX?
 

Those plug-in fuses are convenient but expensive. Just replacing missing ones can take a lot of money at over $5 a pop, and if they start blowing and you have to troubleshoot, it can get quite painful. If you are willing to solder in a leaded fuse that looks like a small resistor you can save a lot of money, which is what I did years ago? on an HP 8640B signal generator. You do lose the convenience of a plug-in but it costs a lot less. (I wrote about this in my "Idea Exchange" column in the QRP Quarterly, a small ham radio publication, in 2011.)

I have some things to take care of today but I'll pass along some DigiKey numbers later. (The leaded fuses from Littelfuse cost under a dollar each.)

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