Hi Greg, Failure analysis of open traces and wires... This from looking at a couple of large tubes earlier this year...
1) Measure capacitance anode to element and compare with a known good tube. I found significant reduction in capacitance on an element with a break in the lead near the tube base. 2) I've also been able to resolve about 1 mm on a failed trace using a Keysight 53220A counter for crude TDR... Have done the same with a Stanford Research SR-620... many others models will work as well - especially if you don't need such fine resolution. I was looking for length differences in the mm range on the end of a 3' BNC cable. The relatively long cable gave me nice separation between outgoing edge and the reflection. Launch a fast edge into the trace to encourage a pronounced reflection... I used a 2.5 V positive going pulse with about 1 nS rise and fall times fed with a very short connection to a "T" at the counter input. Input to counter DC coupled and 50 Ohm terminated. Fast edge then routed from the BNC "T" at the counter input into the trace being measured. I measured the time difference between the primary falling edge (triggering the interval counter at around 1.5V falling) and the rising edge of the reflected wave (triggering around -250 mV rising). I had the counter average a couple hundred samples allowing me to resolve down to ps differences and about a mm resolution... Compared interval from DUT and traces of known lengths on units with cuts at known points (exacto knife). It helped setup to first put the BNC "T" at a 50 Ohm terminated scope input to see the waveform with reflection and to get a good idea of trigger points... then move the BNC to the counter input. Numbers above are approximate and from memory. Best regards, Bob -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/179c0d3d-6ed5-4d4b-83ba-f2d2011d178a%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
