Tektronix 2236 , Won't power up , makes sounds .
 

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 .

Tektronix 2236 , Won't power up , makes sounds .
 

" wrote in news:f57df5eb-4033-
:

Hey all ,
Well the power supply schema is similar to 2215, pretty much any
22XX .

except for 2205,2210.


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 .



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

Tektronix 2236 , Won't power up , makes sounds .
 

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 .

Tektronix 2236 , Won't power up , makes sounds .
 

" wrote in news:c0315a44-73c0-
:

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 .


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