Re: My 2465B has arrived + A5 Board leaky caps cleanup

tekscopegroup@...
 

Gentleman,

Thank very much to all of you for all the information provided. I managed to get the scope screen back to life by replacing the two 10.0K 0.1% resistors (R2012 and R2013) in the DAC resistor reference voltage chain. Also replaced R2016 1.0K as it was pulled out by mistake but tested good. Both 10K resistors where open, and I had to use 5% 1206 parts I had on hand just to test if I was going to be successful to fix the DAC volatges, altough the resistors I used are nowhere near the required specs but close enough for the scope to boot without any errors. Everything done by hand soldering with a T7 fine tip and a Weller 35W pencil iron dialed down to reduce the tip temperature. I do quite a bit of 1206 and SOT-23 parts installations, so the experience gave me the confidence to proceed here as well. In the end those resistors where practically trying to jump off the board with the iron by just reflowing them with fresh solder on both ends. So all in all they where very easy to remove, and zero damage to any pads. I did not attempt to correct the DAC reference voltages yet, no point doing so until the proper parts arrive. They where at +1.3848v and -1.2688v, not even near on-spec.

Posted a couple of updated pictures on the photo album:
https://groups.io/g/TekScopes/album?id=76874

Checked a bit the scope accuracy and it was not too bad at all, given the ref voltage errors, but I am not sure this would also affect the accuracy of the cursors as well? On the new picture you will see a 500nS/Div sweep speed but cursors set at two divisions read 973nS. Of course I now realize that I should have spread the cursors out further, in which case the error seemed to get numerically much smaller. Also ordered a new DS1225AD-150 and a 3M socket, although at some point eventually would very much like to go the FM16W08 way.

My Mouser parts order went out earlier today to get these two resistors and also other parts involved in the general exposed area to the leaking caps, just to have them handy. Of course I also ordered the replacement for the 4 filter caps. I chose to order SMD Aluminum Organic Polymer Electrolytic Capacitors which look very much like the original ones. Also ordered the two power line safety caps, in case mine are of the "fishy smell" type. I have not yet checked the PS board to see what type I got. Recommended subs where to get Kemet Polyester 0.1uF 300V Safety Capacitors. Will also check ripple on all the main DC power rails at J119. Scope will probably need some help with the filter caps, as traces seem a bit fuzzy at times, although they look very much sharper when the 20MHz limit is enabled.

Just in case last night I also copied the EXER 02 values by taking a video while scrolling through all the values 00-FF, and even took them down the old fashion way on paper and pencil. EXER 05 indicates this scope has only seen 360 hours of On time, and 125 power cycles (those last 25 are probably mine). From the writings and labels on the front cover and one side of the scope it looks like this was a designated field instrument that probably did not go out that much. The insides are pristine, and cosmetically the outside and front panel controls are in very good shape. Maybe the A/B timebase Sec/Div concentric knobs feel a bit wiggly, maybe a nut or something will have to be tightened inside? I am also glad the so very important front panel cover was included, and the always good to have pouch. No probes unfortunately.

Once the parts order arrives, and I get a chance to throw them on the board, will update this thread again.
Any comments/suggestions always appreciated.

Alex

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