New kit in the shop: Tektronix 1240 logic analyser (teardown & repair) - Page 1
Forum section: electronics / repair

author: wkb
author_rank: Super Contributor
timestamp: March 12, 2012, 03:37:32 pm
content: Last Saturday I picked up the Tektronix 1240 logic analyser that had been sitting at a friend of mine for (at least) the last decade or so.It had a small problem, selftest error on the soft keys. That proved to be an easy fix. It uses a CRT (this is 1980s technology after all). In front of that CRT is a mesh of infrared lightbeams that are interrupted by the user pointing his/her finger at the displayed softkey. No fancy capacitive touchscreen or whatnot. The LEDs/phototransistors had been covered with the nasty black grime that CRTs seem to specialise in. After cleaning things everything proved to be A-ok, with the added benefit of a brighter & sharper screen.The plain push buttons were also somewhat sticky, so I decided to clean the keypad PCB while it was disassembled anyway.

author: wkb
author_rank: Super Contributor
timestamp: March 12, 2012, 03:41:41 pm
content: Given all the dust I saw at the cooling fan I decided to clean the various logic boards as well. This is 1980s stuff, so tons of TTL which tends to dissipate the odd Watt or 2.It is driven by a 8088 and a Z80, you will notice them on the attached pictures, along with a ton of UV-EPROMs.It has a nice hinged card cage, very practical for service. Less practical are the 1E6screws that hold things in place. In its lifetime it has apparantly seen quite some service, and quite a few of the Pozidriv screws had worn-out headsI replaced those with fresh ones.The large metal 'hockey puck' is a special battery to power the NVRAM. Apparantly these are somewhat notorious for leaking extremely corrosive chemicals, which destroys the PCBs they sit on. Mine were OK, 2.8Volts roughly.The same batteries are also used in the RAM packs for this analyser model. Both my 2 8Kbyte (wow..) RAM packs proved to be OK. They hold 4x a 6116 2K SRAM chip. The RAM packs can hold analyser settings, acquired analyser data etc.

author: wkb
author_rank: Super Contributor
timestamp: March 12, 2012, 03:50:52 pm
content: The guts of an analyser pod.Looks like some really fancy custom hybrid. Break one and you are fubared..

author: wkb
author_rank: Super Contributor
timestamp: March 12, 2012, 03:51:45 pm
content: And the end result, cleaned, lubed and (apparantly) happy

author: tekfan
author_rank: Frequent Contributor
timestamp: March 12, 2012, 05:32:01 pm
content: The ''don't care'' button on logic analysers cracks me up every time. Looks like a nice retro logic analyser.Be sure to back up (if you have a programmer) the EPROMs if the thing craps out in several years time.That hybrid board in the pods seems very high end even for today

author: wkb
author_rank: Super Contributor
timestamp: March 12, 2012, 06:08:27 pm
content: I found the original sales blurb for it.As for the EPROMs, I do have an EPROM gang programmer. It is probably older than the Tek1240, it has a fancy blue VFD display.If it still works I can at lease clone the EPROMs. I don't think I can connect the programmer to a computer.

author: T4P
author_rank: Super Contributor
timestamp: March 12, 2012, 07:50:24 pm
content: "Don't Care" (HAHAHAHAHAHAHAHAHA)Engineers still had humour back then ! ( Oh , tektronix still has ... )As far as i knew , most brand names DSO's all has their own easter eggsBut anyway ,the TH construction is extremely neat !