Re: [dead tek 485] Can i fix it ? (newbie here)


Hi *,
it's really a pleasure to receive so many answers on my first uncomplete post !

Ok. Tried again this morning to power the 485 up and it came alive !!
Here is a status of what i can see on the general status of this unit :

=> The scope was supposed to be in working conditions but needed checking and calibration. No tek probes provided.
Following calibration procedure found on the group, what I can see is :
. several light indicators are not working : x1 led on channel 1, 1Mohm/50ohm indicators on both channels,
. intensity control (top most left) does not work properly : at CCW position I already get a brillant trace on the CRT, at CW position the trace is totally blurrish, focus and astygmatism controls seems to be working (but I don't know if the resulting trace has a normal decent thickness...)
. slope level (B triggering) is not working : it does not change the triggered signal.

=> Concerning the cal signal display (BNC cable used here) :
* channel 1 (1Mohm/50ohm selector pushed, no light indication)
I do not get a full 5 div display - 4,8 div instead. I do not get 1 horiz div per half square wave - 1st half wave is 1div, but others are more in 1.4 long (I did not find a proper way to attach a picture ? :( ).
If 1Mohm/50ohm is in released position, i only get a "line" on the CRT.
* channel 2 (1Mohm/50 ohm selector in released position ??)
As mentioned, Slove level switch has no effect on the signal (triger is done on positive no matter the swich position).
I get almost a 5 div vertical display and the same horiz behaviour as channel 1.
If 1Mohm/50ohm push button is "in" (pushed) : the square wave is not correctly displayed (bottom part of the square wave ??)

=> Concerning the power Off/on not working
If I power off the unit, I'm able to power it on after a delay : probably the time capacitors get discharged ?

=> Concerning Instruction/service manual, I got my copy from :

I'm affraid that this unit has multiples issues...

Will probably start by the PSU one.

Thanx again, and look forward reading your comments.


Join to automatically receive all group messages.