Did I blow up my scope?? - Page 1
Forum section: electronics / repair

author: tedwebb
author_rank: Newbie
timestamp: February 24, 2022, 01:44:28 am
content: I was tinkering with an RF control circuit and couldn't get it to work. So I dug out my Tek 2465 scope that hasn't been turned on in about ten years to do some signal tracing. I plugged it into the handiest power outlet which happened to be my computer surge suppressor power strip. Then I turned the scope on, all seemed normal, I probed the scope's square wave voltage calibrator, it looked pretty good, I wanted to optimize the square wave with the probe adjustment, but didn't have a tuning tool handy. So I'm thinking to myself, I'll just put the probe ground alligator clip to ground to see if the square wave cleans up a bit. Around the time I placed the ground clip to the outer shell of the channel input BNC, I heard loud pops and saw lots of smoke. I didn't notice any sparking at the ground clip. I immediately unplugged the scope.!!So my first question, did I cause this malfunction by placing the scope probe ground clip to ground or was it just an unfortunate coincidence?My second question, is the following a sensible approach:1. Take the covers off and do a power-off visual inspection2. Replace any visually suspect components3. Then with cover off, power up and check for smoke.4. Replace any suspect components5. Then with power on and isolation transformer connected, do voltage checksI have some electronics background but no experience with troubleshooting switch mode power supplies. Anyone recommend any books, web sites, youtube videos that cover troubleshooting / repair of Tek 2465 SMPS???

author: bdunham7
author_rank: Super Contributor
timestamp: February 24, 2022, 01:52:16 am
content: You were only connecting the probe to the scope itself, right? In that case you didn't do anything wrong and likely the capacitors in the power supply inlet filter just blew up. Open it up, clean up the mess and remove the capacitors (the scope works without them if they are the ones I said) and try it out. Never run the scope without the case on unless you have a strong fan blowing on it underneath. And if you need to remove the fan impeller, research this and be 1000% sure you understand the procedure, otherwise you will break the unobtanium fan collet and you'll be dead in the water.Edit: Post photos!

author: xrunner
author_rank: Super Contributor
timestamp: February 24, 2022, 01:59:14 am
content: Quote from: tedwebb on February 24, 2022, 01:44:28 amAs was said you didn't cause it, it just popped due to a component failure. Do your inspection with it unplugged and let us know what you find inside.

author: tggzzz
author_rank: Super Contributor
timestamp: February 24, 2022, 10:06:34 am
content: This is the classic RIFA capacitor failure. They can leave carbon deposits on the PCB, which ought to be removed.Down load the service manual to see how to remove the PSU board.Beverycareful about how you remove the infamous fan - breaking the collet isveryeasy.For the capacitors, and probably the series resistors, see the CondorAudio document. Ensure you use the correct X/Y grade.While you are in there, consider replacing the electrolytics. Be aware one of them is incorrect in the manual, so replace them one at a time.There are many descriptions of all those points, both here and on TekScopes.

author: grumpydoc
author_rank: Super Contributor
timestamp: February 24, 2022, 01:23:12 pm
content: Quote from: tggzzz on February 24, 2022, 10:06:34 am+1Instructions how to do it.

author: tedwebb
author_rank: Newbie
timestamp: February 25, 2022, 07:36:28 am
content: Thank you gentlemen for all the prompt and helpful replies. Each one is sincerely appreciated and will provide some fantastic guidance on my scope repair journey. I will be posting photos of what I found after I have removed the covers. I'm pretty much a rookie at this component level repair business, but have been around airborne radar system and assembly level troubleshooting for a number of years, first in the USAF, the at Texas Instruments. I'm pretty excited about "getting back on the bench". Again, I thank each and everyone of you for your comments and recommendations. I was so relieved to discover that the popping and smoke was a coincidence and not caused by something stupid I had done!!!Ted