{"id":2492,"date":"2009-11-19T08:24:42","date_gmt":"2009-11-19T16:24:42","guid":{"rendered":"http:\/\/www.mightyohm.com\/blog\/?p=2492"},"modified":"2022-12-28T14:18:55","modified_gmt":"2022-12-28T22:18:55","slug":"test-equipment-pr0n-the-hp-3312a","status":"publish","type":"post","link":"https:\/\/mightyohm.com\/blog\/2009\/11\/test-equipment-pr0n-the-hp-3312a\/","title":{"rendered":"Test Equipment Pr0n: The HP 3312A"},"content":{"rendered":"

A few weeks ago, I purchased an HP 3312A 12MHz function generator<\/a> for the lab.\u00a0 After living without a decent signal source for years, I figured that it would bepo handy to have a good general purpose function generator around.\u00a0 A quick visit to eBay and a few clicks later, one was on the way.<\/p>\n

Unfortunately, when I first powered it up, the output was clamped to one supply rail and the sync output was giving me a much-too-large, out of spec voltage swing.\u00a0 D’oh!<\/em><\/p>\n

The generator was sold as-is (like most test equipment on eBay), so I decided to take a crack at fixing it myself.\u00a0 Armed with a barely intelligible, poorly scanned-faxed-photocopied copy of the 3312A service manual<\/a> that I downloaded from Agilent’s website<\/a>, I loosened two captive screws and slid the top and bottom covers off the unit.<\/p>\n

What I found inside really blew me away.\u00a0 What follows are some snapshots of the unit.<\/p>\n

The 3312A is the most elegantly designed and well-preserved piece of electronic test equipment I that have ever owned.\u00a0 The circuit boards, which look brand new, use entirely two-layer\u00a0 through-hole construction and are laid out with generous component spacing and helpful silkscreen labels.\u00a0 There is no inter-board wiring to prevent quick removal of any of the PCBs; all of the wiring harnesses use straightforward connectors.\u00a0 Connections between the top and bottom PCBs are via clever gold plated removable posts that extend through the center panel of the instrument chassis.\u00a0 The chassis itself, which is cast aluminum, is light but sturdy.\u00a0 Every aspect of the instrument design appears to have been carefully thought out and is perfectly executed.<\/p>\n

Here’s the 3312A on the bench, ready for some serious troubleshooting action:<\/p>\n

\"HP<\/p>\n

The aforementioned aluminum chassis.\u00a0 Very nice!<\/p>\n

\"HP<\/p>\n

When I flipped the generator over, I immediately noticed a problem.\u00a0 Here are the remains of four 200 ohm, 1W carbon resistors, burnt to a crisp:<\/p>\n

\"HP<\/p>\n

These resistors provide an internal 50 ohm termination for the sync output, and explain why the sync voltage swing was out of spec.\u00a0 A quick trip to Jameco<\/a> for some new 200 ohm power resistors and the sync problem was fixed.<\/p>\n

The broken main generator output took some more serious troubleshooting.\u00a0 One of the emitter follower transistors that drives the push-pull output driver was burning hot to the touch and a good candidate for replacement.\u00a0 An hour of troubleshooting with the diode test function of my Fluke 87V identified one of the push-pull transistors had failed as well.\u00a0 This is the device that had failed short and was clamping the output voltage to the -15V supply rail.<\/p>\n

The final push-pull drivers are shown here; they are the two devices with the largest heatsinks.\u00a0 The emitter followers are the two metal can transistors just to the left.<\/p>\n

\"HP<\/p>\n

I was able to find suitable replacements for the failed transistors at Jameco<\/a>.\u00a0 Neither of the original devices were still available but I was able to find some devices that were “close enough” by examining a few datasheets and cross reference guides.\u00a0 With the faulty output devices replaced, the generator powered up and was good as new!<\/p>\n

Here’s another couple shots of the main PCB.\u00a0 Gorgeous gold-plated traces and component layout, and some pretty components too:<\/p>\n

\"HP<\/p>\n

\"HP<\/p>\n

Here’s a shot of the inside of the generator with the top (modulator) PCB removed so you can see the header posts that connect the top and bottom PCBs.\u00a0 The center aluminum plate that holds the pins in place is also removable.\u00a0 This allows for rework of components on the bottom (main) PCB without disassembling the entire instrument.\u00a0 Cool!<\/p>\n

\"HP<\/p>\n

Want to see more?\u00a0 Check out the 3312A repairs album<\/a> on flickr!<\/p>\n","protected":false},"excerpt":{"rendered":"

A few weeks ago, I purchased an HP 3312A 12MHz function generator for the lab.\u00a0 After living without a decent signal source for years, I figured that it would bepo handy to have a good general purpose function generator around.\u00a0 A quick visit to eBay and a few clicks later, one was on the way. … Continue reading Test Equipment Pr0n: The HP 3312A<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[5],"tags":[298,34,223],"class_list":["post-2492","post","type-post","status-publish","format-standard","hentry","category-electronics","tag-hp","tag-photos","tag-test-equipment"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pioCd-Ec","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":2476,"url":"https:\/\/mightyohm.com\/blog\/2009\/10\/guess-the-cable-length-to-win-stickers\/","url_meta":{"origin":2492,"position":0},"title":"Guess the cable length to win stickers!","author":"Jeff","date":"October 8, 2009","format":false,"excerpt":"Part 1: An HP 3312A function generator is connected to an Agilent DSO1014A oscilloscope via a length of coaxial cable.\u00a0 The function generator is set to generate a square wave of frequency 1MHz. Based on the screen capture below, what is the length of the coax cable? The first person\u2026","rel":"","context":"In "Electronics"","block_context":{"text":"Electronics","link":"https:\/\/mightyohm.com\/blog\/category\/electronics\/"},"img":{"alt_text":"Unterminated Cable","src":"https:\/\/i0.wp.com\/www.mightyohm.com\/blog\/wp-content\/uploads\/2009\/10\/10v_unterm.png?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":3541,"url":"https:\/\/mightyohm.com\/blog\/2011\/01\/tips-for-finding-test-equipment-service-manuals\/","url_meta":{"origin":2492,"position":1},"title":"Tips for finding test equipment service manuals","author":"Jeff","date":"January 20, 2011","format":false,"excerpt":"When I buy a piece of electronic test equipment, the first thing I do is turn it on and see if it works. \u00a0This is the moment of truth: was that awesome eBay find the killer deal I thought it was? \u00a0(Hint: If it's missing case screws and came with\u2026","rel":"","context":"In "Books and Resources"","block_context":{"text":"Books and Resources","link":"https:\/\/mightyohm.com\/blog\/category\/books-and-resources\/"},"img":{"alt_text":"2009:10:01 02:23:53","src":"https:\/\/i0.wp.com\/mightyohm.com\/files\/flickr\/3972358391_f92e1e1539.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":3522,"url":"https:\/\/mightyohm.com\/blog\/2011\/01\/alis-surplus-stuff\/","url_meta":{"origin":2492,"position":2},"title":"Ali’s Surplus Stuff","author":"Jeff","date":"January 10, 2011","format":false,"excerpt":"Over the holidays I had a chance to visit Ali's Surplus Stuff in Sacramento, CA. This is my kind of place. \u00a0Surplus electronics piled from floor to ceiling. \u00a0Lots of oscilloscopes and useful stuff mixed in with bizarre industrial equipment. Lots of cool rack-mounted equipment here. \u00a0Lots of push-buttons too.\u2026","rel":"","context":"In "Books and Resources"","block_context":{"text":"Books and Resources","link":"https:\/\/mightyohm.com\/blog\/category\/books-and-resources\/"},"img":{"alt_text":"Ali's Surplus Stuff","src":"https:\/\/i0.wp.com\/mightyohm.com\/files\/flickr\/5292042735_4c04635c0e.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":3955,"url":"https:\/\/mightyohm.com\/blog\/2011\/05\/test-jig-for-the-hv-rescue-shield\/","url_meta":{"origin":2492,"position":3},"title":"Test Jig for the HV Rescue Shield","author":"Jeff","date":"May 8, 2011","format":false,"excerpt":"This weekend I threw together a simple test jig for the HV Rescue Shield. The completed jig is shown above. \u00a0There are four header pins, one at each corner, that are used to align the \u00a0BUT, or board under test. \u00a0The Kapton tape insulates the two bottom standoffs from shorting\u2026","rel":"","context":"In "Electronics"","block_context":{"text":"Electronics","link":"https:\/\/mightyohm.com\/blog\/category\/electronics\/"},"img":{"alt_text":"HV Rescue Shield Test Jig","src":"https:\/\/i0.wp.com\/mightyohm.com\/files\/flickr\/5701469806_cc888e3507.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":4772,"url":"https:\/\/mightyohm.com\/blog\/2012\/02\/feed-your-geiger-readily-available-radioactive-test-sources\/","url_meta":{"origin":2492,"position":4},"title":"Feed your Geiger: Cheap and Readily Available Radioactive Test Sources","author":"Jeff","date":"February 14, 2012","format":false,"excerpt":"Want to check if your freshly-assembled MightyOhm Geiger Counter kit is working? You'll need something radioactive! But why pay over $100 for a professional test source when there are plenty of cheap and readily available radioactive items available at your local antique store or online? The disadvantage of using these\u2026","rel":"","context":"In "Kits"","block_context":{"text":"Kits","link":"https:\/\/mightyohm.com\/blog\/category\/kits\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/mightyohm.com\/blog\/wp-content\/uploads\/2012\/02\/6167948098_581ddf3d7d.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":2777,"url":"https:\/\/mightyohm.com\/blog\/2010\/03\/photos-of-the-black-hole\/","url_meta":{"origin":2492,"position":5},"title":"Photos of The Black Hole","author":"Jeff","date":"March 2, 2010","format":false,"excerpt":"Last May, my brother and I went on a week-long roadtrip across the US.\u00a0 Ambling down the highway in a very large moving truck, we travelled from California to Texas by way of\u00a0 Tuscon, Socorro, Albuquerque, Santa Fe, Los Alamos, and quite a few rest stops, gas stations, and fast\u2026","rel":"","context":"In "Electronics"","block_context":{"text":"Electronics","link":"https:\/\/mightyohm.com\/blog\/category\/electronics\/"},"img":{"alt_text":"The Black Hole","src":"https:\/\/i0.wp.com\/mightyohm.com\/files\/flickr\/3516374199_6467b52aba.jpg?resize=350%2C200","width":350,"height":200},"classes":[]}],"_links":{"self":[{"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/posts\/2492","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/comments?post=2492"}],"version-history":[{"count":14,"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/posts\/2492\/revisions"}],"predecessor-version":[{"id":15887,"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/posts\/2492\/revisions\/15887"}],"wp:attachment":[{"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/media?parent=2492"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/categories?post=2492"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mightyohm.com\/blog\/wp-json\/wp\/v2\/tags?post=2492"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}