Re: New member with a currently-dead 2465


Siggi
 

On Fri, Jul 10, 2020 at 12:31 PM Vincent Mallet <vmallet@...> wrote:

Thanks Siggi. The scope is a 2465 300Mhz, S/N B027189. I don't see any smd
components on the A5 board.

Yeah, only (some of) the -B version has SMD on the A5 board, as I
understand.


I don't think the scope has any options but I'm
not too sure how to tell yet.

I looked at the joints of the oscillating circuit components under a
microscope and they looked fine (to my untrained eyes); I tested
conductivity between leads around this area and it matched expectations. I
wiggled things a bit and flexed the board very gently and powered things
back on, still a flat line there.
Well then, I guess you need to dig in, see what's up. In your shoes I'd
start by verifying that U2556 is getting 5V and ground.
You should then be able to check whether the U2556A inverter is driving
its output by measuring the voltages on pin 1 & 2. It should be safe to
test the inverter by shunting its input to +5V and GND through - say - a
100Ohm resistor to see whether it can drive both up and down.
Maybe you want to test R2571 & R2573 as well as C2572. There have been
cases where these 0.1uF capacitors have gone leaky, and that might be
enough to bring down this oscillator.

Good luck,
Siggi

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