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HP 400F Power Supply Troubleshooting Help Needed!
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Technical Ted:
If you like YouTube videos you might enjoy watching this one on his HP 400F.



Ted
factory:

--- Quote from: Technical Ted on August 20, 2023, 04:20:25 pm ---In my unit, the transistors in question are actually marked with EBC for the leads. Don't know about the earlier versions of the A2 board...

Ted


--- End quote ---

Here is the 00400-66504 Rev B board in mine (617 prefix), picture was taken a few years ago, I can't tell you what part the small dome style transistors are ATM.
It has a few signs of older repairs, one of the Sprague 150D tubular solid tants is now a crappy bead tant.

David
Technical Ted:
This seems like a good time to share, so here's mine. Sorry, I removed the -26V jumper and soldered in leads for shorting and connecting a 560 ohm resistor to load the supply during troubleshooting so you might have trouble reading the part number. My 400F is a 0950- (no A designation) series serial number. I have a scanned copy of what I believe is the correct version of the manual for this unit which is a huge file but much better quality. The newest manual from Keysight's site does have a little more information than this version though... i.e. using the 560 ohm resister to load the power supply... The nerd that I am I actually read both.  :)

Ted
David D:

--- Quote from: factory on August 20, 2023, 08:47:46 pm ---
--- Quote from: Technical Ted on August 20, 2023, 04:20:25 pm ---In my unit, the transistors in question are actually marked with EBC for the leads. Don't know about the earlier versions of the A2 board...

Ted


--- End quote ---

Here is the 00400-66504 Rev B board in mine (617 prefix), picture was taken a few years ago, I can't tell you what part the small dome style transistors are ATM.
It has a few signs of older repairs, one of the Sprague 150D tubular solid tants is now a crappy bead tant.

David

--- End quote ---

Better a crappy bead tant than a shorted tubular one!  ;D  Luckily, the Sprague tubulars are still available on Mouser and Digikey. I just gotta figure out what else to order since I hate spending that much money on shipping for one capacitor...  :palm:
David D:

--- Quote from: Technical Ted on August 20, 2023, 10:08:42 pm ---This seems like a good time to share, so here's mine. Sorry, I removed the -26V jumper and soldered in leads for shorting and connecting a 560 ohm resistor to load the supply during troubleshooting so you might have trouble reading the part number. My 400F is a 0950- (no A designation) series serial number. I have a scanned copy of what I believe is the correct version of the manual for this unit which is a huge file but much better quality. The newest manual from Keysight's site does have a little more information than this version though... i.e. using the 560 ohm resister to load the power supply... The nerd that I am I actually read both.  :)

Ted

--- End quote ---

I wish I had the patience to read all the manuals cover to cover, but my attention span is only getting worse the older I get  :(  My doctor says that's normal for someone with ADHD. It might be "normal" in my case, but as my grandfather used to say, "Getting old isn't embarassing, it's just damned inconvenient".  :(

I didn't load my power supply output after I removed the jumper since it was evident that loading wasn't the issue with mine.

Here's my board mid-troubleshooting:

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