Hey all , Well the power supply schema is similar to 2215, pretty much any
22XX .when i turn on the scope it makes high pitches noise in a rate of about one sec , tsk.....tsk.....tsk....
the line filter is ok , diode bridge is good .
what could be the problem ? something shorts the PS .
" snipped-for-privacy@gmail.com" wrote in news:f57df5eb-4033- snipped-for-privacy@q33g2000hsh.googlegroups.com:
except for 2205,2210.
The PS is a switcher,and will go into "burst" mode(current limit) if overloaded.
it could be a shorted rectifier diode,or some bad electrolytic caps;their ESR goes too high. Caps and diodes are the most common PS problems.
A bad HV multiplier could also be the problem.
The PS first rectifies mains voltage to DC(127-350VDC),then PWMchops it and charges a cap to ~43v DC,uses that to run an inverter oscillator that generates the secondary supplies. the pre-reg current limits at around 650ma in the 2215,in the 2236 it may be 1A,don't know for certain. the 2230/2232 digital scopes limit at ~1.3A.
-- Jim Yanik jyanik at kua.net
well i fixed it , it was one of the Transistors (Q939) , shorted the PS , also the fan was dead ... i guess the stuck fan overloaded the PS , so i replaced the fan too .
thanks .
" snipped-for-privacy@gmail.com" wrote in news:c0315a44-73c0- snipped-for-privacy@n36g2000hse.googlegroups.com:
a TEK mandatory mod was to cut off the Molex connector to Q9070,and solder the 3-wire ribbon directly to the FET. The Molex would turn brown and burn up.
IIRC,they also changed zener VR935 to a 56V zener to keep it from turning on the crowbar SCR too early. Of course,you could just teepee a diode or 2 in series with the zener to raise the zener point a volt or so.
-- Jim Yanik jyanik at kua.net
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