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465M won't trigger

Larry Tusoni W6YH #16389 My 465M would not trigger a few months ago so I found a used trigger board and installed it and it worked fine. I haven't used it since then, and today, it won't trigger again just like before. It has been stored in my humidity/temperature controlled shop so I am not sure how this can happen so any ideas would be appreciated. Thanks, Larry
Craig Cramb All Messages By This Member #16391 开云体育 it won't trigger again just like before Larry,? My thought is there probably is something up with the power supply. ?Ive worked on a bunch of these and the can caps seem to fail or get marginal on the power supply rails. Its pretty easy to check power supply voltages. Remove top cover and there is three DC power supply posts along with the ground post just behind the 115 vac power switch. ?you can also check the 95v opposite side just in front of the aluminum barrier. ?Connect DVM to common and each tap measure DC, then switch meter to AC and check again for voltage. ?This should help you get an understanding if power supply is problem. Craig toggle quoted message Show quoted text On Jul 14, 2023, at 12:26 PM, Larry Tusoni W6YH <larry@...> wrote: ?My 465M would not trigger a few months ago so I found a used trigger board and installed it and it worked fine. I haven't used it since then, and today, it won't trigger again just like before. It has been stored in my humidity/temperature controlled shop so I am not sure how this can happen so any ideas would be appreciated. Thanks, Larry
Larry Tusoni W6YH #16392 开云体育 On Jul 14, 2023, at 2:08 PM, Craig Cramb <electronixtoolbox@...> wrote: it won't trigger again just like before Larry,? Hi Craig My thought is there probably is something up with the power supply. ?Ive worked on a bunch of these and the can caps seem to fail or get marginal on the power supply rails. Its pretty easy to check power supply voltages. Remove top cover and there is three DC power supply posts along with the ground post just behind the 115 vac power switch. ?you can also check the 95v opposite side just in front of the aluminum barrier. ?Connect DVM to common and each tap measure DC, then switch meter to AC and check again for voltage. ?This should help you get an understanding if power supply is problem. Great thanks. You know I did check at least some of the voltages according to the manual before I installed the replacement trigger board so It is probably a good idea to do it again before I use it for target practice! ;-) I loved the scope and it has worked for me for 20+ years so hate to be without it but it is so frustrating to have the same problem again with it just sitting in my shop. Regards, Larry Craig On Jul 14, 2023, at 12:26 PM, Larry Tusoni W6YH <larry@...> wrote: ?My 465M would not trigger a few months ago so I found a used trigger board and installed it and it worked fine. I haven't used it since then, and today, it won't trigger again just like before. It has been stored in my humidity/temperature controlled shop so I am not sure how this can happen so any ideas would be appreciated. Thanks, Larry -------------------- Among God's creatures two, the?dog and the guitar,? have taken all the sizes and all the?shapes, in order? not to be separated from the man. -- Andres Segovia ? Larry's Personal Email Amateur Radio: W6YH larry@...? 209.736.9197 Angels Camp, California Earth-Planet, Universe
Craig Cramb All Messages By This Member #16393 so frustrating to have the same problem again with it just sitting in my shop. I have a shop full of test equipment that sometimes I just cannot get to the bottom of the problem so it gets moved to the side for an easier repair on another unit. But then get back to it later when you have more mental space to look deeper into an issue. I like the 465M as there isn't to much of an issue of a transistor coming loose in a socket since all parts are soldered into the board. ?I have spent days trying to pin down issues on vintage equipment like many members of this group but here is where you hopefully get some help. ?Do some PS checks and advise your findings along with cycling all push buttons to help clear any oxidation. Craig
Dave_G0WBX All Messages By This Member #16394 Hi. It could be a simple bad interconnect between boards/cables etc.? I recall from my time at Tek, that some of those semi-gold plated "Harmonica" connectors would become intermittent over time. You moved it about when fitting the substitute board, and it all worked.? Now, things have "relaxed" a bit over time, and gone faulty again. Try a gentle poke (with an insulated stick) at the boards and interconnects and see if anything shows itself as a culprit. 73. Dave G8KBV. -- Created on and sent from a Unix like PC running and using free and open source software:
paul larner All Messages By This Member #16407 if i was you i would check all power rails using a digital multi meter set to ac volts,that will show the ripple voltage indicating a bad cap.
Dave_G0WBX All Messages By This Member #16408 OK. Ripple on the power rails is unlikely to prevent a scope from triggering, but it could make things a little weird. Plus, would show up as other troublesome symptoms. Yes, PSU (and other) caps can/do fail from time to time, but often in ways that causes minor issues before total failure. Much more common, are bead Tantalum caps on power rails failing short cut. Regards. Dave G8KBV (Ex TEK UK, during the era of the 465 etc.)

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