content/hp34970a.rst

Thu, 05 Nov 2020 22:15:16 +0100

author
David Douard <david.douard@sdf3.org>
date
Thu, 05 Nov 2020 22:15:16 +0100
changeset 128
aba381b2bac9
parent 115
6b6e13653348
child 130
56ffb9577050
permissions
-rw-r--r--

Fix several inter-document links

and normalize use of absolute path for {static} and {filename} links.

58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
1 =================================
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
2 HP 34970A Data Acquisition Unit
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
3 =================================
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
4
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
5 :Author: David Douard
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
6 :Category: Electronics
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
7 :Tags: HP, 34970A, DMM, repair, test equipment
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
8 :series: HP 34970A repair
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
9 :series_index: 1
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
10
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
11
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
12 I recently "scored" a HP 34970A with the DMM included and 2 plugin
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
13 cards (HP 34901A and HP 34907A) for less than 200€. The plugins should
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
14 be in working condition, but the main switch unit was almost "given"
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
15 with the plugin modules since it is non functional.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
16
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
17 .. image:: {static}/images/hp34970a/front-view.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
18 :alt: front view of the HP 34970A data acquisition unit
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
19
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
20 It's in very good shape, the front panel and the push buttons are
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
21 clean. The knob is nice but it has a rough step when turning it for a
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
22 complete revolution.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
23
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
24 When powered up, however, things are a bit nastier... The VFD is, as
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
25 often with these equipment, very dim and the digits tend to puke on
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
26 the others. In fact, it's mostly unreadable, and the unit beeps
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
27 several times, signs of errors (which I cannot really read them see on
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
28 the display).
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
29
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
30 Internals
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
31 =========
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
32
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
33 The unit consists in 4 parts:
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
34
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
35 - the main logic/cpu board on the bottom left side,
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
36 - the DMM module, juste above the main board,
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
37 - the frontpanel and
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
38 - the back plane where plugin modules are connected.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
39
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
40 .. image:: {static}/images/hp34970a/bottom-view.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
41 :alt: bottom view of the HP 34970A
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
42
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
43 .. image:: {static}/images/hp34970a/top-view.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
44 :alt: top view of the HP 34970A with DMM removed
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
45
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
46 .. image:: {static}/images/hp34970a/dmm.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
47 :alt: DMM module of the HP 34970A
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
48
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
49 The front panel hold the keyboard, the rotary encoder and the diplay system.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
50
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
51 .. image:: {static}/images/hp34970a/front-panel.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
52 :alt: front panel of the HP 34970A
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
53
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
54 The front panel is managed by a 80C51 (a 87C51 actually)
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
55 microcontroller. It's responsible for handling the keyboard and
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
56 feeding the shift registers of the VFD drivers (a pair of
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
57 HV518PJ). The communication with the main CPU is a serial line with
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
58 opamps to adjust the signal levels.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
59
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
60 The chips are PLCC44 located under the VFD are the drivers:
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
61
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
62 .. image:: {static}/images/hp34970a/front-panel-pcb.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
63 :alt: front panel PCB of the HP 34970A
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
64
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
65 On my unit, the voltage levels for the VFD are fine. I suspected that
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
66 one of the 2 VFD drivers (the one responsible for driving the grids)
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
67 were partially failing, so I ordered a pair of new drivers, as well as
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
68 some PLCC sockets. It was my first real smd revork. I though that it
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
69 might be easier to cut the pins of the soldered chip, but it was not a
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
70 good idea, I peeled 2 pads on the PCB. Thanksfully, they were not
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
71 broken. So I've undoldered the other VFD with my new cheap hot air
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
72 soldering station, and it's been way easier and did not damage the PCB
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
73 at all... Lesson learned.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
74
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
75 After that first real SMD unsoldering experiment came the first SMD
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
76 soldering: install the plastic made PLCC sockets... I was not sure
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
77 wether to use the hot air gun or my Weller soldering iron, nor what a
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
78 correct temperature for the hot air station whould be adequate. The
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
79 informations on the socket datasheet were not very clear to me.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
80
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
81 So I gave a try (I think at around 280°C). The sockets seemed properly
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
82 soldered, but in fact, a few pins were not making contact. So I
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
83 decided to cut the bottom of the socket (which is essentially useless)
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
84 so I can more easily rework these "cold" pins with my soldering iron.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
85
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
86 The tricky part of installing these PLCC sockets is that decoupling
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
87 capacitors (C6, C7, C9 and C10) are a bit too close, so I had to move
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
88 them.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
89
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
90 .. image:: {static}/images/hp34970a/front-panel-sockets.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
91 :alt: PLCC sockets for the VFD drivers of the HP 34970A
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
92
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
93
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
94 Now I had to try to rejuvenate the tungsten filaments. Like for old
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
95 CRT (and even for triodes), the filament, which is responsible for
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
96 emiting electrons toward the anode (coated with phosphor) tend to be
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
97 polluted and loose their emissive power. A common trick to "clean"
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
98 them is to apply a much higher voltage than rated so they shine for a
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
99 few seconds. One mst be careful not to burn them, otherwise the VFD is
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
100 definitively lost.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
101
115
6b6e13653348 content: use {static} instead of {filename} in image paths
David Douard <david.douard@sdfa3.org>
parents: 58
diff changeset
102 .. image:: {static}/images/hp34970a/vfd-back.jpg
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
103 :alt: back side of the VFD (probably dead) module
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
104
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
105 So I tried such a rejuvenation on my VFD module. I wasn't sure what
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
106 color the filaments must be heated to (between a light orange to an
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
107 almost white yellow). I was doing this using my `Lambda PSU
128
aba381b2bac9 Fix several inter-document links
David Douard <david.douard@sdf3.org>
parents: 115
diff changeset
108 <{filename}/LPD422FM.rst>`_ raising the voltage while looking at the
58
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
109 filaments.
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
110
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
111 The results are very disappointing. The VFD is a little bit brighter,
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
112 but the spilling over between digits is now much worse...
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
113
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
114 I guess this VFD module cannot be saved, after all...
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
115
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
116 So I've been thinking of a plan B, and I think I'll try to replace the
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
117 VFD display with a blue 256x32 OLED module. It's smaller (I cannot
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
118 find a module near the size of the VFD display), but it should still
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
119 be quite readable. Indeed, that requires a bit of work: I plan to
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
120 build an arduino-based adapter (using an arduino micor) that will take
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
121 place of the VFD drivers (then be fed by the serial-to-shift registers
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
122 outputs of the 80C51). One other solution is to replace the 80C51 with
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
123 a newly programmed one, but I think reverse ingineering the serial
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
124 communication between the front-panel microcontroller and the main CPU
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
125 would require much more work. Since it's a 87C51, I doubt I can easily
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
126 dump it's ROM...
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
127
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
128
58e79464cd09 [hp34970a] new blog post about the HP 34970A
David Douard <david.douard@logilab.fr>
parents:
diff changeset
129 Meanwhile, next step is to take care of all these errors.

mercurial