Re: 7904 Mainframe damaged

Velik Kazakov
 

This week I play with one "new" 7904. It come with fired tantalum cap in Control Illum power supply. After exchanging the cap and checking of the ps and main frame all looks ok. But when put new ps in my old working 7904 it work, but all two PS installed in the new main frame power after few seconds (sometimes 10+ seconds). All checking in the main frame looks good. Maybe this main unit is not powered for long time and now have a caps inside that need more time/energy to energize. It start only w/o plugins and control illum must be off. After it power one time. I shut it off and install plugins and power on. Now all is ok. Maybe you can try to power main unit for 5-10 seconds waiting in tic mode. Maybe have the same problem. If need can make a video to show the situation with this new 7904. Old one I repair and recap in 08/2017 and it work well (here is teh repair and cleanif of it https://www.eevblog.com/forum/repair/tektronix-7904-repair-and-restoration/).

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