MacGyver, eat your heart out :) - Page 1
Forum section: electronics / general

author: AlfBaz
author_rank: Super Contributor
timestamp: September 06, 2013, 04:05:56 am
content: You do what you can...

author: marshallh
author_rank: Unknown
timestamp: September 06, 2013, 04:59:12 am
content: I spy a 93XXWHat's wrong with it

author: AlfBaz
author_rank: Super Contributor
timestamp: September 06, 2013, 05:33:01 am
content: That hybrid chip may be busted. It takes a signal in, normalises it for the adc and produces 3 differential signals. one to the trigger cct the other 2 to separate adc's (interleaved sampling?).Aside from the signal it has digital control lines from the mpu as well as some analogue control voltages for gain and offset from a scanning dac.Unlike the other channels this didn't have any output but I just found that the calibration voltage is appearing on the output so there may be hope for it yet. There also seems to be an intermittent problem with the adc/data gathering mcu for that channel which leads me to believe that the main cpu is not getting any calibration information for that channel so ots not setting the gain and offset voltages correctly, and that's possibly why I'm not getting a signal outIf any of that crap made sense to you then... How are you Marshall buddy, pal

author: AlfBaz
author_rank: Super Contributor
timestamp: September 06, 2013, 11:41:42 am
content: Yay Its fixed!!Turns out my assumptions were correctThe ADC hybrid fed the channels converted signal data to a demultiplexer which stuffed the data into the ram boards. The scope complained of ADC failure but its data just wasn't making it to the memory because of bad pin connections to the pads. Seems like lecroy decided to skimp on solder paste. On super close inspection it almost looked like the IC pins were sitting on the pads without any solder.At any rate it appears that the main controller did not see any data coming back from the calibration routine so it turned the gain right down to prevent overly large signals making it to the sample and hold cct's

author: digsys
author_rank: Unknown
timestamp: September 06, 2013, 12:10:04 pm
content: Great job. Maybe I should pay you to fix mine, and I have the service manual :-) I'm waay too lazy.It just recently developed a heat fault. You anywhere near Melbourne? :-)

author: AlfBaz
author_rank: Super Contributor
timestamp: September 06, 2013, 12:29:33 pm
content: Quote from: digsys on September 06, 2013, 12:10:04 pmNo, if I was I would of applied for that job you were advertising(it was you wasn't it?) I'm up in NSW near Wollongong

author: free_electron
author_rank: Super Contributor
timestamp: September 06, 2013, 12:33:12 pm
content: Problem is these things run so hot they tend to desolder themselves over time.... The solder becomes brittle and cracks.Flux-it and resolder it.

author: digsys
author_rank: Unknown
timestamp: September 06, 2013, 12:47:30 pm
content: Quote from: AlfBazOh yeah .. bummer :-)

author: AlfBaz
author_rank: Super Contributor
timestamp: September 06, 2013, 01:01:16 pm
content: Quote from: free_electron on September 06, 2013, 12:33:12 pmYeah that's what I was contemplating as my next step before I completely re-assemble it but it's working right now so I just want to bask in its functioning glory for a moment before I potentially f*ck it completely