Electronics > Repair
Tektronix TDS754D - acquisition board test fail
<< < (8/8)
Rax:
It worked flawlessly for part of the afternoon, on and off. Then tonight I fired it up again, and it gives me the artifacts on screen (see below) and essentially the same error regarding U208 as before (see below), just with a slightly different address.

Back to the drawing board. I feel I need to check U208 thoroughly for input/address and the rest of the pins. Maybe replace it with another one I have here, just in case this one's taken a dive.
Rax:
Some progress last night.

I'm now not sure how I fixed the short or what exactly is going on, I've found a "short" between what I think are another two pins of U208 (but always on the address pins). I think last time it was 3 and 4 or maybe 4 and 5. It's possible that was indeed a solder bridge.

But this time around my meter beeped a short between 2 and 3 (A14 and A16). Per 520B component level SM, the address buses are shared between U201 through U208, and then separately U209 through U216. So my "pin 2 and 3" short could be with my recently replaced U208 (where the utility flags it), but could also be originating at U207.

I removed U208, and I have the same "short." I call it "short" because in closer examination resistance there is almost 10 ohms, which I can't imagine is caused by a solid short, even at a relatively remote point from where I measure it (so through traces). Besides, it's 10 ohms at the U207 pins as well as on the currently free pads of U208 (it being lifted).

Any ideas welcome.
Navigation
Message Index
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod