comparison: content/hp3456a.rst
content/hp3456a.rst
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| 28 procedure requires a Signature Anayzer (which I obviously don't have). | 28 procedure requires a Signature Anayzer (which I obviously don't have). |
| 29 I briefly tried to dig the signals with my cheap USB logic analyzer, | 29 I briefly tried to dig the signals with my cheap USB logic analyzer, |
| 30 but the readings were quite disappointing. I was considering | 30 but the readings were quite disappointing. I was considering |
| 31 implementing a signature analyzer using a Nucleo STM32 board, since I | 31 implementing a signature analyzer using a Nucleo STM32 board, since I |
| 32 have several of them for my `HP 34970A display replacement project | 32 have several of them for my `HP 34970A display replacement project |
| 33 <{filename}/hp34970a.rst>`_. | 33 <{static}/hp34970a.rst>`_. |
| 34 | 34 |
| 35 Suddenly, I realized I did not even check the power rails! And | 35 Suddenly, I realized I did not even check the power rails! And |
| 36 bingo, the +33V was dead (something like 5V). | 36 bingo, the +33V was dead (something like 5V). |
| 37 | 37 |
| 38 Ok, much better, a power supply failure is a way better | 38 Ok, much better, a power supply failure is a way better |
| 39 news. Especially since this kind of device uses a linear power supply: | 39 news. Especially since this kind of device uses a linear power supply: |
| 40 | 40 |
| 41 .. image:: {filename}/images/hp3456a/psu.jpg | 41 .. image:: {static}/images/hp3456a/psu.jpg |
| 42 :alt: HP 3456A's power supply board | 42 :alt: HP 3456A's power supply board |
| 43 | 43 |
| 44 Yes, it is very dusty. | 44 Yes, it is very dusty. |
| 45 The culprit appeared in plain sight as soon as I removed the power | 45 The culprit appeared in plain sight as soon as I removed the power |
| 46 supply board (A10) from the unit: | 46 supply board (A10) from the unit: |
| 47 | 47 |
| 48 .. image:: {filename}/images/hp3456a/psu_C7.jpg | 48 .. image:: {static}/images/hp3456a/psu_C7.jpg |
| 49 :alt: failing caps on HP 3456A's power supply | 49 :alt: failing caps on HP 3456A's power supply |
| 50 | 50 |
| 51 The schematic is very straighforward; few bridge rectifiers, some | 51 The schematic is very straighforward; few bridge rectifiers, some |
| 52 capatcitors, some regultators, nothing fancy: | 52 capatcitors, some regultators, nothing fancy: |
| 53 | 53 |
| 54 .. image:: {filename}/images/hp3456a/psu_schematic.svg | 54 .. image:: {static}/images/hp3456a/psu_schematic.svg |
| 55 :alt: schematic of the power supply board | 55 :alt: schematic of the power supply board |
| 56 | 56 |
| 57 The dead capacitor is C7 (47µF, 50V, Sprague). I also checked the | 57 The dead capacitor is C7 (47µF, 50V, Sprague). I also checked the |
| 58 other capacitors on the board, and noticed some of them were not very | 58 other capacitors on the board, and noticed some of them were not very |
| 59 tight. A quick inspection of the solder layer showed a few "cold" | 59 tight. A quick inspection of the solder layer showed a few "cold" |
| 67 noname brand... I'll have to order some better replacement caps next | 67 noname brand... I'll have to order some better replacement caps next |
| 68 time I have to purchase on DigiKey or Mouser. | 68 time I have to purchase on DigiKey or Mouser. |
| 69 | 69 |
| 70 Whatever, after this quick recap, the 3456A is back alive: | 70 Whatever, after this quick recap, the 3456A is back alive: |
| 71 | 71 |
| 72 .. image:: {filename}/images/hp3456a/1.0011v.jpg | 72 .. image:: {static}/images/hp3456a/1.0011v.jpg |
| 73 :alt: 1.0011V | 73 :alt: 1.0011V |
| 74 | 74 |
| 75 And even better, it look much more stable than it used to be! | 75 And even better, it look much more stable than it used to be! |
| 76 | 76 |
| 77 For example, here a plot of my Geller Voltage Reference a few month ago: | 77 For example, here a plot of my Geller Voltage Reference a few month ago: |
| 78 | 78 |
| 79 .. image:: {filename}/images/hp3456a/geller_2016_02.svg | 79 .. image:: {static}/images/hp3456a/geller_2016_02.svg |
| 80 :alt: 10V | 80 :alt: 10V |
| 81 | 81 |
| 82 and now: | 82 and now: |
| 83 | 83 |
| 84 .. image:: {filename}/images/hp3456a/geller_2016_11.svg | 84 .. image:: {static}/images/hp3456a/geller_2016_11.svg |
| 85 :alt: 10V | 85 :alt: 10V |
| 86 | 86 |
| 87 | 87 |
| 88 It's time for a nice enclosure for my Geller Labs reference now. I | 88 It's time for a nice enclosure for my Geller Labs reference now. I |
| 89 also still have in my todo list a DC reference built around a AD5791 | 89 also still have in my todo list a DC reference built around a AD5791 |
