content/hp8904a_2.rst

Sun, 27 Mar 2016 23:36:30 +0200

author
David Douard <david.douard@logilab.fr>
date
Sun, 27 Mar 2016 23:36:30 +0200
changeset 45
3eed12f6592b
parent 44
96b26fb52f0b
child 115
6b6e13653348
permissions
-rw-r--r--

[tek] part 2 of the PSU repair

24
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
1 ========================================================
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
2 HP8904A Multifunction Synthetizer Repair: 10MHz output
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
3 ========================================================
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
4
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
5 :Author: David Douard
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
6 :Category: Electronics
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
7 :Tags: HP8904A, repair, test equipment, signal generator
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
8
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
9 After having `fixed the PSU of one of my HP8904A`_ signal generator, I
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
10 discovered that the other unit had its 10MHz reference output
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
11 dead flat.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
12
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
13 I've disassembled the main logic board, but unfortunately, the
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
14 schematic of this later A2 board (as it is referenced in the servce
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
15 manual) is notavailable in any available HP's manual...
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
16
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
17 The board I have is the second revision:
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
18
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
19 .. image:: {filename}images/hp8904a/A2_top.jpg
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
20 :alt: The logic board (A2) of the HP8904A signal generator.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
21
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
22 And the bottom side of the PCB:
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
23
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
24 .. image:: {filename}images/hp8904a/A2_bottom.jpg
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
25 :alt: Bottom side of the A2 board.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
26
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
27 According to the presence of soldering flux, it looks like the U46
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
28 chip (a 74ALS73CN) on this board has been replaced:
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
29
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
30 .. image:: {filename}images/hp8904a/A2_U46.jpg
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
31 :alt: The U46 chip seems to have been replaced.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
32
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
33 After having moved my scope probe around the 10MHz output (J102), I've
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
34 found that the most probable culprit is the Q106 transistor (which
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
35 seems to be a bipolar one). The 10MHz arrives to the base signal, the
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
36 emitter is grounded, but nothing on the collector...
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
37
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
38 Unfortunately, HP had the awful habit of taging most of the parts in
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
39 their test equipments with custom references, even if most of them are
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
40 in fact regular parts.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
41
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
42 The problem was then to identify a reasonable replacement part for
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
43 this puppy. It presents itself as a Motorola with weird reference
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
44 ``3 0659``:
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
45
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
46 .. image:: {filename}images/hp8904a/HP8904A_Q106.jpg
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
47 :alt: The failing transistor.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
48
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
49 Having no luck searching the net, I've asked the `wonderful EEVBlog
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
50 community`_ for some help identifying this transistor. My question
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
51 obviously was answered very quickly by several fellows. First I've had
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
52 the correct reference for the transistor. Its HP part number is in
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
53 fact 1853-0659 (notice the 3-0659 as stamped on the transistor case),
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
54 and it is i fact a simple 2N3906.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
55
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
56 But another forum member also noted that a wire was broken, as it is
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
57 clearly visible on the picture above.
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
58
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
59 So I did a very quit fix for this problem by simply resoldering the
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
60 broken leg of the transistor, and bingo, the 10MHz output is working
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
61 again!
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
62
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
63 This EEVBlog community really is awesome!
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
64
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
65 .. _`fixed the PSU of one of my HP8904A`: {filename}/hp8904a.rst
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
66 .. _`wonderful EEVBlog community`: http://www.eevblog.com/forum/repair/repair-of-an-hp8904a-signal-generator
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
67
89689c6e9cf4 [hp8904a] add two blogs about the HP8904A and a small update of the about page
David Douard <david.douard@logilab.fr>
parents:
diff changeset
68

mercurial