Re: Tek 2430 Works Fine for 15mins Then Freezes


Steven Bender
 

Hi John,

I have a 7603 that is a mainframe scope which did something similar, 15 to 30 minutes then frozen. I also have some 2445’s that do need caps and/or possibly diodes.

The 7603 had 2N3055 or similar TO-3 pass transistors, due to decades of heat, solder on their B and E pins became faulty, needed solder removal and resoldering.

On a 24xx first look for silver cased 100 uF. / 25 vdc low volt caps, they are a known problem in the 2445, check the associated 3A shottkey diodes on "diode test". Look for any darkened “Burn Marks” on PS circuit board.

I have some non-tek units from the 1980’s which gave lots of yellow/orange drop tantalum bypass caps, across Op Amp voltage lines that are usually +/-15 volt or +/-18 volt lines and elsewhere - tantalums, that had impurities in their manufacture, which 2, 3, or 4 decades later will either glow, burn black, or smoke, damaging nearby trimmers, or other parts, typical and definite signs of a failure, partial short, or dead short. As such, for 16 volt, 20 volt, or 25 volt tantalum parts, replace with similar value 35 volt parts, usually cures it. While electrolytic have also improved over the decades, to change to an electrolytic, in general triple the value, and expect to replace again in twenty years :-).

Steven

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