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content/hp8662a_2.rst
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| 1 =============================================== | |
| 2 HP8662A Synthetized Signal Generator - Part 2 | |
| 3 =============================================== | |
| 4 | |
| 5 :Author: David Douard | |
| 6 :Category: Electronics | |
| 7 :Tags: HP8662A, repair, test equipment, HP, Generator, RF | |
| 8 :series: HP 8662A | |
| 9 :series_index: 2 | |
| 10 | |
| 11 This is the part 2 on my series about my HP 8662A Signal Generator. | |
| 12 After fixing the PSU, several more problems needed to be addressed: | |
| 13 | |
| 14 - a few sloppy keys on the keypad, | |
| 15 - the know did not work at all, | |
| 16 - and more importantly, some very unpleasant spectrums at some frequencies | |
| 17 (covered in part 3). | |
| 18 | |
| 19 | |
| 20 Keypad | |
| 21 ====== | |
| 22 | |
| 23 The keypad was, as allways with HP devices from this period, very hard and | |
| 24 "clunky" for most keys but 2. | |
| 25 | |
| 26 No surprise: these keys were missing their famous (well, for some at least) spring: | |
| 27 | |
| 28 .. image:: {filename}images/hp8662a/key_missing_springs.jpg | |
| 29 :class: image-process-large-photo | |
| 30 | |
| 31 As you can (not) see, the "Status" key as well as the "Increment Set" key have | |
| 32 no spring at all. | |
| 33 | |
| 34 While I was cleaning the unit, I've been half-lucky and found one of the 2 | |
| 35 missing springs. But I had to figure a solution for the other missing one. | |
| 36 | |
| 37 I thought about: | |
| 38 | |
| 39 - buying a replacement key: the ones I found are ridiculously expensite, | |
| 40 - buying a front panel for an HP gear from this era: might be a reasonable approach, | |
| 41 - looking for ready made springs: could not find, | |
| 42 - asking some custom made ones from a company making springs: got a few | |
| 43 responses, one of them quite reasonable even for small quantities (between 3 | |
| 44 to 5€ each). | |
| 45 | |
| 46 While I was looking for a solution, I also gave a try to a simple solution: cut | |
| 47 a replacement "spring" from a plastic wrap. I tried several wraps (of several | |
| 48 widths), and I found one that seems to work just fine, and the feeling is about | |
| 49 the same as original keys: | |
| 50 | |
| 51 .. image:: {filename}images/hp8662a/key_hack.jpeg | |
| 52 :class: image-process-large-photo | |
| 53 | |
| 54 .. image:: {filename}images/hp8662a/key_hack_anim.gif | |
| 55 | |
| 56 I cleaned all keys using some deoxit contact cleaner which also lubricated | |
| 57 those noisy springs making the keys nice ans smooth again. | |
| 58 | |
| 59 | |
| 60 Rotary encoder | |
| 61 ============== | |
| 62 | |
| 63 The rotary encoder was not working at all, and once again, a classical failure | |
| 64 for those old HP gears: the small bulb used as light source for the optical | |
| 65 encoder was dead. | |
| 66 | |
| 67 I tried to replace it with a 3mm LED I had in my junk box, but it did not work, | |
| 68 so I bought a few replacement bulbs on ebay, and sure enough, the encoder is | |
| 69 now working ok (not perfectly, there are some missed steps: there are two small | |
| 70 screws that look like adjustment screws, but I'm not sure how to tune them). | |
| 71 | |
| 72 .. image:: {filename}images/hp8662a/encoder.jpeg | |
| 73 :class: image-process-large-photo |
