Electronics > Repair
HP54600B with spike problem with and without signal
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sacha:
Thanks Tim, you're giving me a lot of advice to think about, in any case I think the best way is to try to understand the cause before intervening with the removal of the components. At the moment I only have the new Ram available. As soon as I can I will take measurements using OE/WR as trigger. I wonder what changes in the reading when using pin 20 (S) as the trigger of this memory?

these are the links to the videos on youtube
I don't know if they can be useful because I didn't use the trigger on the pins recommended by Tim

https://youtube.com/shorts/J2vYJLIUjlc?feature=share
https://youtube.com/shorts/Ifw9fT1vDFY?feature=share


below you can see my latest little one who arrived today :-)
T3sl4co1l:
Looks nice and periodic, but who knows what the edges are doing.

To clarify: you need a range under 100ns/div at least, to even begin to resolve the edges.  A 100MHz scope may not be sufficient to resolve it, either.

Tim
sacha:
Hi, I made the measurements with the trigger on pin 22 and I see clean signals on the rising and falling edges. But on pin 20 I see this signal.

https://www.youtube.com/shorts/3bgqQN2jaMc
T3sl4co1l:
The other pins look fine, sharp rise, no wobblies?

Whatever's driving (or not) might be open-collector/drain style, and the waveform is normal; it only matters how long, and when, /S is below threshold, and the rise might not matter.  You'll have to trace back the source and see what type of driving pin it is.  It is definitely not a normal waveform for a CMOS driving pin.

Tim
sacha:
I don't see those noises on the address pins or even on the in/out pins. I'll try to understand where that signal is coming from

the photos you see were taken on pins 9 and 11 of the memory
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