diff --git a/content/electronics/repair-hp-34401A-bench-multimeter.md b/content/electronics/repair-hp-34401A-bench-multimeter.md new file mode 100644 index 0000000..cd91bda --- /dev/null +++ b/content/electronics/repair-hp-34401A-bench-multimeter.md @@ -0,0 +1,59 @@ ++++ +date = "2017-12-01" +title = "Repair: Hewlet Packard 34401A Bench Multimeter" +tags = ["repair", "electronics", "equipment"] +categories = [ "Electronics Repair" ] +description = "After watching The Signal Path for some I decided to treat myself to a classic 34401A 6½ digit multimeter." ++++ + +![The HP 34401A Bench multimeter](/img/hp-34401A-front.jpg) + +I've been watching [The Signal Path](http://thesignalpath.com/blogs/) for quite a while now and +I _really_ like the repair videos. After doing a lot of audio repairs I wanted to give electronics +test equipment a try. + +The Agilent/HP/Keysight 34401A is a very popular bench multimeter with decent specs: + + * 6½ digit resolution + * 10 measurement functions: DC/AC voltage, DC/AC current, 2- and 4-wire resistance, diode, continuity, frequency, period + * Basic accuracy: 0.0035% DC, 0.06% AC + * 1000 V max voltage input, 3 A max current input + +After scouring the internets for a few weeks I finally found an auction for a defective unit _and won_. +The description simply stated DC current measurement did not work. No word on the other fuctions +whatsoever. + +When I got the unit in the mail I prepared to make a Youtube video of this repair. Well, +the repair turned out to be _so_ easy it's barely worth this blogpost, let alone a whole Youtube +video. + +First things first, I took the cover off and took a peek inside. Very clean and nothing out of the +ordinary there. + +![The insides of the HP 34401A Bench Multimeter](/img/hp-34401A-insides.jpg) + +Next I powered the unit on and ran a self test (hold the `shift` button when powering the unit on). It +passed. + +Next I started with some measurements: DC voltage, resistance, frequency, continuity. All good. Then I +was time to check DC current. Nothing. Open circuit. Well, guess what's the first thing to check when +a fused circuit is open? + +![The bad fuse. 250V 3.0A](/img/hp-34401A-bad-fuse.jpg) + +Yeah. The fuse. It's a 250V 3.0A fuse in a holder located on the back of the unit. It was blown. There's +also a 7.5A fuse inside of the unit for extra protection, but this fuse turned out to be fine. + +![The fuse is located on the back](/img/hp-34401A-fuse.jpg) + +Well, I put in a new fuse and voila, DC current measurement is working again. Here's a picture of the +unit testing a 5.0V reference IC. + +![Testing my 5.0V Voltage Reference](/img/hp-34401A-test-5V.jpg) + +For those interested, it's an Intersil [ISL21090BFB850Z](https://www.intersil.com/content/dam/Intersil/documents/isl2/isl21090.pdf) +which I plan to put in a box. The IC generates 5.0V ±0.025% whereas the HP 34401 is specified with a basic 0.0035% accuracy. + +So the 5.0016V reading is well within spec. Nice! + +Next question: keep it or sell it? I haven't decided yet. diff --git a/static/img/hp-34401A-bad-fuse.jpg b/static/img/hp-34401A-bad-fuse.jpg new file mode 100644 index 0000000..898165e Binary files /dev/null and b/static/img/hp-34401A-bad-fuse.jpg differ diff --git a/static/img/hp-34401A-front.jpg b/static/img/hp-34401A-front.jpg new file mode 100644 index 0000000..93dee39 Binary files /dev/null and b/static/img/hp-34401A-front.jpg differ diff --git a/static/img/hp-34401A-fuse.jpg b/static/img/hp-34401A-fuse.jpg new file mode 100644 index 0000000..29237ef Binary files /dev/null and b/static/img/hp-34401A-fuse.jpg differ diff --git a/static/img/hp-34401A-insides.jpg b/static/img/hp-34401A-insides.jpg new file mode 100644 index 0000000..b0cb8d0 Binary files /dev/null and b/static/img/hp-34401A-insides.jpg differ diff --git a/static/img/hp-34401A-test-5V.jpg b/static/img/hp-34401A-test-5V.jpg new file mode 100644 index 0000000..c9a9085 Binary files /dev/null and b/static/img/hp-34401A-test-5V.jpg differ