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Tek 2235 trace problem

J

James Seamore

Jan 1, 1970
0
After a few months in storage, my beloved Tek 2235 scope now only
shows a quick burst of a trace, or spot of light, on power up and then
the screen goes blank.

Without asking for too much detail, is this something worth having a
look at to fix, and, if so, what is the most likely fault?

Can I assume the tube is still good?

Thank you kindly for any advice.

James S.
 
J

Jim Yanik

Jan 1, 1970
0
After a few months in storage, my beloved Tek 2235 scope now only
shows a quick burst of a trace, or spot of light, on power up and then
the screen goes blank.

Is the power supply making any noises,like a "chirp" or clicking?
Without asking for too much detail, is this something worth having a
look at to fix, and, if so, what is the most likely fault?

Yes,it's worth fixing.

1st;check power supply voltages and ripple.(especially the 2kv cathode V.)
Bad electrolytics are a common problem here,ESR climbs.
Then determine if the trace is off-screen,either vertically or
horizontally;could have a bad metal film resistor in the vertical amp or
horizontal amp(or a lead fell off a pin!).You can short the CRT vertical
pins(blue/brown wires) together to see if the trace reappears,same for the
horizontal pins.(red/green wires)
Can I assume the tube is still good?

It sounds OK.
Thank you kindly for any advice.

James S.


One important thing is to get a service manual for that model,it has
schematics,parts lists,a NICE circuit description to tell you how it works.
You may be able to download a copy from the BAMA website.
 
T

tekamn

Jan 1, 1970
0
Jim said:
Is the power supply making any noises,like a "chirp" or clicking?

Yes,it's worth fixing.

I definetely agree.
1st;check power supply voltages and ripple.(especially the 2kv cathode V.)
Bad electrolytics are a common problem here,ESR climbs.
Then determine if the trace is off-screen,either vertically or
horizontally;could have a bad metal film resistor in the vertical amp or
horizontal amp(or a lead fell off a pin!).You can short the CRT vertical
pins(blue/brown wires) together to see if the trace reappears,same for the
horizontal pins.(red/green wires)


It sounds OK.


One important thing is to get a service manual for that model,it has
schematics,parts lists,a NICE circuit description to tell you how it works.
You may be able to download a copy from the BAMA website.

for the power supply schematic: pwr supplies of Tektronix scopes
2215/2215A and 2235 are very similar, so one of the BAMA docs should be
helpful.

hth,
Andreas
 
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