240C Power Resistor Decade Box

[Hoopty]

FYI

FAMs,

Please pass on to all your PMELs.

It has recently come to our attention that there may be a possible safety issue/concern regarding the 240C Power Resistor Decade Box commonly found in many of your PMELs.

During two assessments that are currently in progress, three (3) of these items were tested IAW TO 33K2-4-26-1, step 3.3 Withstand Voltage Test and all three failed.  Further investigation today revealed that a 240C owned by the AFPSL also failed in February 2005 for the same test. 

The test requirement in step 3.3.6 of the calibration procedure is for less than/equal to one (1) milliamp; readings between 60 to 100 milliamps have been encountered thus far. 

Chief Truax has directed that MLC evaluation teams make this unit a special interest item during their current MCA assessments to collect more data.

Recommend you consider directing your PMELs to remove their 240Cs from service until the units have been tested and found to meet preliminary requirements in the calibration procedure-this check takes less than 5 minutes to perform.

AFMETCAL is currently investigating further to determine the extent of the problem and who we will need to coordinate with regarding assets not owned by the PMELs (Item Manager, Equipment Specialist, technical order OPR, etc.).

If the FAMs would like to consolidate the results from their respective PMELs, you can forward the results to me for consolidation until we have determined the extent of the problem and the OPR for the effort.

[flamy78]

I've never cal'd these but how can this be a sudden discovery? What's the interval? These are what 40 years old?

Or is it something they've been limiting and shouldn't have been? Guess I'll find out more. Wonder if us contractors will get this e-mail.

[Thraxas]

I've never cal'd these but how can this be a sudden discovery? What's the interval? These are what 40 years old?

Or is it something they've been limiting and shouldn't have been? Guess I'll find out more. Wonder if us contractors will get this e-mail.

Maybe step 3.3 is a recent change. Maybe somebody smoked one. Maybe AFMETCAL is just looking for more work to give us. People find problems with equipment all the time, and this one apparently took longer to find. If they're really 40 years old, maybe they're at or past the end of their lifecycle.

Why didn't you search AFCAV for the interval? Weren't you at work when you posted?

[fdas]

I think most bases have them as npc and monitor all outputs. I know here in Korea we have one cald and one npc. So if nobody is calibrating them then there is a good chance nobody is checking them.

[Hoopty]

Can someone look this up?  (I don't have access to any K-pros here at the schoolhouse) 

Off the top of my head, I think that the check in question is a safety check.  Looking for current flow to the case?  Cranking high voltage through the resistor maybe?  I can't really remember.  I may be thinking of the wrong item, but 3.3 is definitely a prelim and has to be a safety issue.

So... if this is the case, NPC or not, that's why they want these items checked out.

[Sparky1]

This is a safety check. A note in the prelims states that there has been problems with insulation breakdown of the internal wiring in these units. Basically your applying 660v @ 60hz between the input terminals and the chassis ground and monitoring the current using a DMM.  Of the 2 units I checked 1 was good to go, the other had a direct short between the input terminals and the front panel. 

[Hoopty]

Thanks Sparky1.

So it would indeed seem that whether your 240C's are cal'd or not, you will want to perform this check.  Unless, of course, you like the added excitment that voltage on the case brings to your daily routine

[flamy78]

I've never cal'd these but how can this be a sudden discovery? What's the interval? These are what 40 years old?

Or is it something they've been limiting and shouldn't have been? Guess I'll find out more. Wonder if us contractors will get this e-mail.

Maybe step 3.3 is a recent change. Maybe somebody smoked one. Maybe AFMETCAL is just looking for more work to give us. People find problems with equipment all the time, and this one apparently took longer to find. If they're really 40 years old, maybe they're at or past the end of their lifecycle.

Why didn't you search AFCAV for the interval? Weren't you at work when you posted?

Nope I never post at work. I've deleted a post and browsed 1 or 2 posts by hoopty that were valuable info we weren't given at work.

What's this AFCAV you speak of?

Any shock that isn't static is better than all the static I generate. Though I understand 400Hz is not fun. I think we need new chairs that don't produce static.

For an extra point What color are they? Flynn cannot answer.

[Thraxas]

Are your chairs covered with shag carpeting or something?

Let me guess...they're those ugly gray or black colored chairs that seem to be so popular in the military.