TEKTRONIX 2430A shorted the ground lead to hot wire 115VAC - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 15, 2017, 06:49:56 am
content: This thing already has at least 1 bad CCD chip for sure(I've swapped their positions), so 1 channel doesn't really work right wrt to gain and Vpos and other stuff too I think. The scope gets "weird" under 100us somtimes on both channels. I'm going to order a CCD this weekend. Triggering is messy too.But then I forgot what I was doing on a little 12V SMPS and touched just the probes ground lead to hot mains 115V for 1-2 seconds. On the SMPS I fried a BR diode, main tank cap, and melted a choke off its pin (the switch and fuse are on the neutral side, the switch was off and never blew the fuse, I touched the neg of the main electro tank cap after the rectifer)Since then I've had some intermittent problems with the traces getting all fuzzy and just "weird" (bedtime, too late to explain). The menu system/programming stuff all seems fine.Would I have cooked some capacitors as the current went from the SMPS into the probe's ground and out the back plug ?At the time, the scope was just booting up and I think the attenuator relays were in default 100mV mode

author: capt bullshot
author_rank: Super Contributor
timestamp: September 15, 2017, 07:48:28 am
content: With these scopes from the good old days, the input BNC shells usually are mounted to the grounded chassis. So the short circuit current is diverted from the input circuitry and usually no damage happens. But beware, there's no rule without exception.

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 15, 2017, 10:50:54 pm
content: I just got it back together after months of using it a table.......ridiculousIt's definitely different since this happened.When AC or DC coupled to various oscilators I made and a little freq gen PCB, after a while power on and me changing v/div and time, the vertical gain goes wacky, with it jumping up above center line for a while, then jumping below for a whileAnd as I change the vert. posit knob, it does this up and down.And it gets very blurry/fuzzy as it goes near the top/bottom off screen on BOTH channels. And it never did that before. Once I get into us/div its really weird.Ch1 drops more or less altogether under 100us (since I owned it I guess)Also the 1V-2V-5V anttenuator circt or its gain pre-ampIDK , seems way off. The signal get blanked out to zero nearly on CH1.Using Ch2 to probe Ch1 at resistor from the annten. to big pre-amp chip, the signal is there but just barely. ?(or well its getting through to ch2 from somewhere)I zapped something extra for sure.Replacement CH1 CCD is orded in the meanttime, for the orginal problem since I got it on ebay.The time scale and trigger has problms too, how much of that is from the CCD IDK.I have only checked a handful of main board voltages, and no wave forms yet.Where should I see a periodic signal corresponding to the input signal....as I probe through the -attenuators-pre-amp-CCD-DAC ?I swapped the CCD's and am writting down the diag. codes both ways. But the main ORIGINAL ch1 gain prob. moves to ch2, so thats the CCD for sure.I swapped the pre-amps, but never noticed much diff...but I must check again.I want to check swap and check inside the antten. and maybe clean some relay contacts or somethingHow does that even come apart? but they are soldered on with mulitlpe pins too;The things not calibrated either, thats another factor on its internal testshere's 1 of many schematic's, but this one has hyperlinks by page so super easy to navican't find it yet??? google messing with mehere's 1 w/o nice interal linkshttp://w140.com/2430-SM.pdfBefore I zapped it ~115V, I would get a nice clean / crisp/sharp trace when looking at 1.2MHz sine wave for example.Lately, it might start out like that, but after me changing ranges, and it heating up or whatever, that nice clean signal on the working CCD goesThe self cal and ext-diag's that fail are all 7000s for the CCDs, and a few PreAmp 8000s failures, and very few 9000s trigger failure codesAt least the computer side seems to work fine