comparison: content/hp8904a_2.rst
content/hp8904a_2.rst
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| 14 schematic of this later A2 board (as it is referenced in the servce | 14 schematic of this later A2 board (as it is referenced in the servce |
| 15 manual) is notavailable in any available HP's manual... | 15 manual) is notavailable in any available HP's manual... |
| 16 | 16 |
| 17 The board I have is the second revision: | 17 The board I have is the second revision: |
| 18 | 18 |
| 19 .. image:: {static}images/hp8904a/A2_top.jpg | 19 .. image:: {static}/images/hp8904a/A2_top.jpg |
| 20 :alt: The logic board (A2) of the HP8904A signal generator. | 20 :alt: The logic board (A2) of the HP8904A signal generator. |
| 21 | 21 |
| 22 And the bottom side of the PCB: | 22 And the bottom side of the PCB: |
| 23 | 23 |
| 24 .. image:: {static}images/hp8904a/A2_bottom.jpg | 24 .. image:: {static}/images/hp8904a/A2_bottom.jpg |
| 25 :alt: Bottom side of the A2 board. | 25 :alt: Bottom side of the A2 board. |
| 26 | 26 |
| 27 According to the presence of soldering flux, it looks like the U46 | 27 According to the presence of soldering flux, it looks like the U46 |
| 28 chip (a 74ALS73CN) on this board has been replaced: | 28 chip (a 74ALS73CN) on this board has been replaced: |
| 29 | 29 |
| 30 .. image:: {static}images/hp8904a/A2_U46.jpg | 30 .. image:: {static}/images/hp8904a/A2_U46.jpg |
| 31 :alt: The U46 chip seems to have been replaced. | 31 :alt: The U46 chip seems to have been replaced. |
| 32 | 32 |
| 33 After having moved my scope probe around the 10MHz output (J102), I've | 33 After having moved my scope probe around the 10MHz output (J102), I've |
| 34 found that the most probable culprit is the Q106 transistor (which | 34 found that the most probable culprit is the Q106 transistor (which |
| 35 seems to be a bipolar one). The 10MHz arrives to the base signal, the | 35 seems to be a bipolar one). The 10MHz arrives to the base signal, the |
| 41 | 41 |
| 42 The problem was then to identify a reasonable replacement part for | 42 The problem was then to identify a reasonable replacement part for |
| 43 this puppy. It presents itself as a Motorola with weird reference | 43 this puppy. It presents itself as a Motorola with weird reference |
| 44 ``3 0659``: | 44 ``3 0659``: |
| 45 | 45 |
| 46 .. image:: {static}images/hp8904a/HP8904A_Q106.jpg | 46 .. image:: {static}/images/hp8904a/HP8904A_Q106.jpg |
| 47 :alt: The failing transistor. | 47 :alt: The failing transistor. |
| 48 | 48 |
| 49 Having no luck searching the net, I've asked the `wonderful EEVBlog | 49 Having no luck searching the net, I've asked the `wonderful EEVBlog |
| 50 community`_ for some help identifying this transistor. My question | 50 community`_ for some help identifying this transistor. My question |
| 51 obviously was answered very quickly by several fellows. First I've had | 51 obviously was answered very quickly by several fellows. First I've had |
| 52 the correct reference for the transistor. Its HP part number is in | 52 the correct reference for the transistor. Its HP part number is in |
| 53 fact 1853-0659 (notice the 3-0659 as stamped on the transistor case), | 53 fact 1853-0659 (notice the 3-0659 as stamped on the transistor case), |
| 60 broken leg of the transistor, and bingo, the 10MHz output is working | 60 broken leg of the transistor, and bingo, the 10MHz output is working |
| 61 again! | 61 again! |
| 62 | 62 |
| 63 This EEVBlog community really is awesome! | 63 This EEVBlog community really is awesome! |
| 64 | 64 |
| 65 .. _`fixed the PSU of one of my HP8904A`: {static}/hp8904a.rst | 65 .. _`fixed the PSU of one of my HP8904A`: {filename}/hp8904a.rst |
| 66 .. _`wonderful EEVBlog community`: http://www.eevblog.com/forum/repair/repair-of-an-hp8904a-signal-generator | 66 .. _`wonderful EEVBlog community`: http://www.eevblog.com/forum/repair/repair-of-an-hp8904a-signal-generator |
| 67 | |
| 68 |
