Combo Mod Hell




Not knowing what the hell I was doing, I decided to start in on one of the eight foot tall monsters. I figured it might be best to just dive in and go for it. So that’s what I did. My list called for three Phase Noise stations and three Combo Mod stations. The Combo Mod plans looked nasty because every inch of available space in the cabinet was used. In the past we had two separate kinds of stations for testing modulation. One was an Analog Modulation set, the other Digital Modulation. Rather than have two stand alone racks engineering redesigned them into a single station and called it Combo Mod. Skimming over the Combo Mod assembly instructions, I took a deep breath and got to work.

At first I was overly cautious. With each instrument I loaded in and secured I went over to double check with Shoelaces to make sure I did shit right. I guess after I had about half of the rack filled up Shoelaces told me he thought something was wrong. He walked over to a complete Combo Mod station over in our test area, looked at it, and came back. Then he checked the assembly instructions I was using and said, “This is ancient. It’s an older version of these stations and the new ones use different instruments.” Fuck! Sure enough I walked over to a couple functional Combo Mod stations in forward flow test and Shoelaces was right. They had different boxes in them compared to what my instructions had in the paperwork. That made me angry.

I called the engineering group to find out what was up with their online documentation. As soon as one of the guys over there picked up the phone I explained that I was working on some Combo Mod stations and that the instructions I was using from their website appeared to not be current. He said, “Yeah, you’re right. We haven’t updated any of those in a long time.” Okay no shit. When I asked why they haven’t kept things updated to the latest version he replied, “We’re too busy.” Nice. I took all of the engineering paperwork I printed out and threw it in the trash. Then I grabbed a Combo Mod station that no one was using, powered it down, and rolled it all the way to the other side of the department where I was working. I would copy everything from that rack visually. Really I couldn’t think of a better way to continue.

I started over again from the beginning.

Installing each piece of equipment was the easy part. The bad shit wasn’t until I got to adding BNC cables inside the cabinet on the back of a switch/control unit. Pure hell. The switch/control unit holds up to 5 circuit boards that can be anything from a multiplexer or general purpose relay to a VHF switch. Regardless of what I installed, each board in the control unit was covered with BNC connectors. Nearly all of them were to be used in the Combo Mod station. The only way to put it together without becoming totally confused as to which cable went where was to add each cable one at a time. I went back and forth dozens of times between the functional Combo Mod rack and the copy I was setting up just to connect those BNCs. Then I must have checked each cable like six damn times because I was paranoid I’d placed them incorrectly.

Shit was running all over the place in there and it started to get cramped fast. I had GPIB cables, power cords, rigid lines, BNCs, and other stuff everywhere. Most frustrating was making cable connections on the inside of a single unit rack cover plate. It was necessary to have some feed-thru connections from inside the rack to the front panel but no matter what order I tried to stage it in, cables didn’t want to reach the threaded connectors. Using longer cables might be okay in some circumstances but it could also cause serious performance issues. I had no way of knowing what was acceptable to alter or not since the engineering assembly instructions were bad. That didn’t leave me much of a choice. The more cramped it got in there the more difficult it was to get a wrench on a connector. I felt like I was working in an engine compartment instead of a test rack.

This shit was going to cause me to become a heavy drinker in no time.


~ by factorypeasant on March 19, 2006.

5 Responses to “Combo Mod Hell”

  1. BNCs are *so* old. I’m amazed they’re still in use. At a print shop I worked in back in 1996, our computers were networked with cables that used BNC connectors. I’m talking about Mac IIci’s and LCIIs and maybe a Quadra. And it was ancient then. We were so happy when we got ethernet.

    British Naval Connector

  2. actually in the test and measurement world they are still widely in use.

  3. Yep, The difference in length of the bnc cables caused a big problem, especially with the external reference. We kept having a problem with the boxes going out of lock. Changed the bnc cable with a new one of the same length. same problem. decided to shorten them up and that fixed it. drug engineering dude over to show him what i found, was told that i couldnt change the configuration of a station without proper authorization. two weeks and 25 meetings later, they agreed that longer cables caused a problem. typical day in the life of an test staion tech, one hour to fix a problem and 100 hours of engineering time to analyze the fix. Oh yeah FP, I want my key back.

  4. Barley- funny you should mention that key. i’m pretty sure i still have it in a dish on my dresser. i’ll bring it with me on the trip up to see you this summer.

  5. If your interested in setting up a limited liability company then please check out my site

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