Power supply problem with Tek 2220
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Hello Tek user,
I am new to this forum. ?However, I have a problem with
my Tek 2220 and Tek 2235 scope at the same time.
Both are facing power supply problems.
?
Let me focus on the tek 2220 and discuss the tek 2235 another
time.
The is the behaviour of the scope.
?
- When power on from cold, the scope
will fire up and a proper trace will appear properly. ?Everything seems
ok.
- However, after a few minutes when
the supply heated up (I am using 230V supply), the power will shut down and
try to fire up and shut down again.
- After I off the set, wait for a
few seconds, and try to on it, the set will not be able turn on but will be
in the on/off mode trying to start and then shut down.
- If I wait longer a minute or
so, it will fire up properly for a longer period (maybe 30 seconds) then
it shuts down into on/off mode.
?
It seems that some overload has happened after firing up that
is related to the temperature.
I have not investigated in detail but these are some test
which shows normal operation
?
Pre-regulator shows 43V stable and correct (between TP940
and TP950)
+5V, -5V, +8.6V, -8.6V, 100V are showing correctly.
?
I do not suspect the EHT because the trace is ok.
The heatsink feels a little hot, but it was that way when it
was working before, so I am not sure.
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Anyone experience the same behaviour and what was the fix?
?
What are possible component failure that could shut down due
to temperature ?
?
What is the expected average current flowing through R907
under normal condition??
I need to check if the load current is ok.?
?
?
Rgds,
Chor Ming
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