# HG changeset patch
# User David Douard <david.douard@logilab.fr>
# Date 1523494514 -7200
# Node ID fd44150ec807a92e98a89e0c5e1a30e4900e34c6
# Parent  90ee7c1f5d08f778d5884555033f246c4fdf723c
[hp8662a] part 2

diff -r 90ee7c1f5d08 -r fd44150ec807 content/hp8662a_2.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/hp8662a_2.rst	Thu Apr 12 02:55:14 2018 +0200
@@ -0,0 +1,73 @@
+===============================================
+ HP8662A Synthetized Signal Generator - Part 2
+===============================================
+
+:Author: David Douard
+:Category: Electronics
+:Tags: HP8662A, repair, test equipment, HP, Generator, RF
+:series: HP 8662A
+:series_index: 2
+
+This is the part 2 on my series about my HP 8662A Signal Generator.
+After fixing the PSU, several more problems needed to be addressed:
+
+- a few sloppy keys on the keypad,
+- the know did not work at all,
+- and more importantly, some very unpleasant spectrums at some frequencies
+  (covered in part 3).
+
+
+Keypad
+======
+
+The keypad was, as allways with HP devices from this period, very hard and
+"clunky" for most keys but 2.
+
+No surprise: these keys were missing their famous (well, for some at least) spring:
+
+.. image:: {filename}images/hp8662a/key_missing_springs.jpg
+   :class: image-process-large-photo
+
+As you can (not) see, the "Status" key as well as the "Increment Set" key have
+no spring at all.
+
+While I was cleaning the unit, I've been half-lucky and found one of the 2
+missing springs. But I had to figure a solution for the other missing one.
+
+I thought about:
+
+- buying a replacement key: the ones I found are ridiculously expensite,
+- buying a front panel for an HP gear from this era: might be a reasonable approach,
+- looking for ready made springs: could not find,
+- asking some custom made ones from a company making springs: got a few
+  responses, one of them quite reasonable even for small quantities (between 3
+  to 5€ each).
+
+While I was looking for a solution, I also gave a try to a simple solution: cut
+a replacement "spring" from a plastic wrap. I tried several wraps (of several
+widths), and I found one that seems to work just fine, and the feeling is about
+the same as original keys:
+
+.. image:: {filename}images/hp8662a/key_hack.jpeg
+   :class: image-process-large-photo
+
+.. image:: {filename}images/hp8662a/key_hack_anim.gif
+
+I cleaned all keys using some deoxit contact cleaner which also lubricated
+those noisy springs making the keys nice ans smooth again.
+
+
+Rotary encoder
+==============
+
+The rotary encoder was not working at all, and once again, a classical failure
+for those old HP gears: the small bulb used as light source for the optical
+encoder was dead.
+
+I tried to replace it with a 3mm LED I had in my junk box, but it did not work,
+so I bought a few replacement bulbs on ebay, and sure enough, the encoder is
+now working ok (not perfectly, there are some missed steps: there are two small
+screws that look like adjustment screws, but I'm not sure how to tune them).
+
+.. image:: {filename}images/hp8662a/encoder.jpeg
+   :class: image-process-large-photo
diff -r 90ee7c1f5d08 -r fd44150ec807 content/images/hp8662a/encoder.jpeg
Binary file content/images/hp8662a/encoder.jpeg has changed
diff -r 90ee7c1f5d08 -r fd44150ec807 content/images/hp8662a/key_hack.jpeg
Binary file content/images/hp8662a/key_hack.jpeg has changed
diff -r 90ee7c1f5d08 -r fd44150ec807 content/images/hp8662a/key_hack_anim.gif
Binary file content/images/hp8662a/key_hack_anim.gif has changed