Troubleshooting Jobs

[LarryFine]

What did I do? All necessary info has been provided here.

Checked the oil reservoir?

 

[kwired]

Checked the oil reservoir?

Or reconnected a "quick connect" coupling in the hydraulic line, turned a valve on, etc.

 

[K8MHZ]

Creative enough that no one else thought of it.... Sorry to disappoint you....LOL

Actually, that is the first thing I thought of.

 

[ptonsparky]

Actually, that is the first thing I thought of.

Count me in there too, but I second guessed myself. I have no qualms about using those devices.

 

[junkhound]

Here is one for yourr light reading - names are A and B to protect the incompetent. Kinda like an internal VFD problem.

3 phase high speed motor drives for a space launch vehicle, drives powered the re-entry control surfaces. Kinda narrows down the companies, eh?
Made and designed by company A , 3 delivered and functioned fine, 2 space flight completed successfully.
4th and 5th units burned up on extensive thermal/vacuum/operational tests.

After 3rd unit, Company A bought by company B on east coast. Hot shot QC guys from B visit A and proclaim some wires are routed incorrectly, insist on changes for units 4 and on.
Units 4 and 5 fail.

Unit 4 wired up to 15 each Tek windows based 4 channel scopes, 2 weeks of looking at waveforms, at least 12 engineers involved. .

Hotshot reroute of wires added 5 nH to inductance (yes, nano, E-9) which resulted when PWM signals turned off motor drive FET the L*di/dt caused an internal current in IR2113 full bridge drivers to burn open an internal trace.

Fix was to change timing to avoid the di/dt. Note not nmentioned befroe was that company A had psent alot of time for the originalwire routing to avoid that scenario, but the company B 'hotshots' insisted and had authority to insist on change. Cost company B a few hundred K to find the problem and implement solution. NASA, company C vehicle contractor, and others involved.

Never have heard if the 'hotshots' got their next pay raise, hah.

 

[junkhound]

Worst are failures that occur only on orbit, and can never be duplicated in a gravity well. All the best stories however are considered proprietary.

 

[hbiss]

Nevermind

-Hal

 

[synchro]

One such story was on some overhead bridge cranes where two 200ft. bridges could be locked together to become like one 400ft. bridge. The mechanism for doing that was a hydraulically driven set of large tapered steel pins that extended from the end of one bridge into sockets on the other. I was there to troubleshoot the PLCs and VFDs, but was pulled into a situation wherein the pin extension was not working. It had a small drive motor for the hydraulics that reversed to extend or retract the pins, no springs or valves. I forced the I/O on the PLC to make the motor turn on in both Fwd and Rev, which it did fine, but no action on the pins. Everyone was blaming the PLC even though I proved that it was working correctly. I then solved the problem in two minutes.

What did I do? All necessary info has been provided here.

Jogged one crane into better alignment with the other to allow pins to move?

 

[Dennis Alwon]

Let's try and put different troubleshooting posers in different threads. It makes it easier