New member with a currently-dead 2465


Vincent Mallet
 

Hi group,

I just joined TekScopes after hunting for info on how to go about
resurrecting a dead 2465 I acquired recently. I picked up electronics as a
hobby a little over a year ago and it has been a learning experience for
sure, and my new challenge is to see if I can do something about this
'scope :)

The 2465 powers on and a lot of lights light up and stay lit on the front
panel; the display stays absolutely blank (no hint of a beam anywhere no
matter the position of the intensity settings). No blinking TRIG'D light,
pressing A/B does nothing (actually, pressing any button doesn't change
anything).

I started getting familiar with the service manual and going through the
basic troubleshooting steps. The power supply measurements appear to be
within specs as per table 5-1; ripples _seem_ to be within spec but I'm not
sure I'm measuring them right with my DSO.

I moved on the troubleshooting steps until I reached the clock signal
coming to U2092-37 (TP505) where I get a flatline rather than a 5MHz
signal. I looked at the oscillator circuit on A5 and the test points at the
output of U2556B and U2468A are both flat lines too (instead of a 10MHz
square and 5MHz square). I do get a -5V on one side of R2553 and +5V on
R2549.

Question: how likely is it that the oscillator circuit has failed? Or could
there be an external factor preventing it from oscillating that I don't see?

My next step would be to pull the few components from the oscillating
circuit out so I can test them but I figured maybe I'd ask around if this
rang a bell first.

Thanks!

Vince.

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