My 2465B has arrived + A5 Board leaky caps cleanup

tekscopegroup@...
 

This is a 2465B Sn 55K purchased off ebay, very good external cosmetics, almost pristine interior with only very few traces of dust and so far have not seen any signs of having been disturbed or repaired in the past. Seller was stating that a Test 05 Fail 40 error was coming up upon power up, and that the traces where showing a lot of vertical jitter and eventually would move off screen towards the bottom. I figured that price and shipping cost numbers where decent for a B version, with the front cover and storage pouch (<$250), given the description, which I figured could be related to the well known leaky caps problem, so went for it and won. Oh and somehow the blue filter was loose and almost fell out when I took off the front cover. Have to check the manual, but I figure the filter just needs to snapped back into the groves that seem to hold it in place? If it is so easy to fall off, no wonder so many scopes are being offered without the blue filter, gone missing.

But today upon arrival when I powered up the scope it does not show a trace at all, or even a readout, nothing at all on screen, so not sure how long ago it still had a live screen. The power up self test does stop at the "ADD" label, so as I understand this seems to match the reported Test 05 scenario error. In any case pulled out the A5 board and got started on the leaky cap mess cleanup following some very good suggestions from Chuck not to try to desolder the caps in one piece, but rather carefully chop them up to get to the pads. Well, I kind of cheated and very carefully lifted the single cap in the corner by desoldering it bit by bit by extremely gently rocking it side by side very little at a time while heating the (cleaned up) pads, as it looked easy to do it on that location. It came out fine. But then decided to heed the recommendations as the other remaining 3 caps looked more difficult to get at due to less space around them. I think in the end all went quite well, there was not too much corrosion damage on the pads, and I could not see any traces that where eaten away.

Off course still quite a few other affected parts with dull/greenish pads that will need to be cleaned or replaced (see pictures liked bellow), and I am guessing that in the case of the IC legs that show corrosion they will have to be cleaned thoroughly. Also once I am done removing the rest of the affected SMD resistors and caps, will wash both the affected areas of the board with dish soap and water with a soft toothbrush. Then its into the oven at 375 deg for 45 minutes. Just kidding... its really only 40 minutes that are needed.

Some A5 pictures here:
https://groups.io/g/TekScopes/album?id=76874

BTW the scope has a TEK U800 (not the less desirable Maxim part), and most ICs show a 1990 date code. The NVRam has a 9020 date code. Once I can sort out the most pressing issues with the inoperative display I'm thinking of going the FM16W08 route, to do away with the need of a backup battery for good. I only hope getting the A5 board back in shape will bring back the screen to life. If not once I'm done with it will start checking voltage rails at J119 as well.

Comments and suggestions very welcomed about any follow up tests to make sure I have possibly not missed anything on the A5 cleanup, any know suspect VIAs to check, or hidden traces to verify they have continuity to another part, etc. Any other obvious possibilities besides the A5 mess on why the screen is non-op?

BTW, noticed that one of the 3 caps had two very fine traces between the pads to which the cap is mounted. I see these traces on one side go to what looks like two test points, but on the other side they seem to end nowhere, and don't seem to be connected to the capacitor pads either. Out of curiosity, anyone know what they are meant for? Thanks for any input.

Alex

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