Got some kind of similar case.the audio of my system with 2 node on it was cracking out of no where, the only thing was a visit to the site for manitenance and a good look at the computer.. cleaning the fan, removing dust checking all connector.. the thing was that we left a usb to keypad/mouse ps2 adaptor plugged in. We usely remove it. this was not even connected to a KB or mouse. but it was puting stress on the USB hub inside the computer.. So could it be that something internal of the mother bord is connected inside the computer on that hub? I am thinking of card reader like SD card?? But thanks for the head up. will keep an eye on this ;-)
Date: Sat, 14 Feb 2015 21:15:13 -0600 From: n5zua@earthlink.net To: App_rpt-users@ohnosec.org Subject: [App_rpt-users] Bizarre Issue
Having worked with app_rpt for the past five years, I've run across most of the common issues that everyone else has. But every once in a while, I run across one that is so bizarre, I feel compelled to post it, so others might know about it. Such was the case yesterday.
I have a site with a cabinet with three repeaters in it. The two meter repeater was installed last as an app_rpt repeater from the beginning, and has never had any issues. The other two are 70 centimeter GE EXEC II mobiles, full duplexed, connected to an RLC-4 controller, with the other two ports being wire line interfaces. Since the wire line has been having intermittent issues lately, I wanted to move the two GE radios to URIs. I built two conversion cables, with a female DB-9 on one end (to accept DB-9 male from radio to RLC controller), and a male DB-25 on the other (to connect to the URI). This leaves the flexibility of going back to the RLC-4, without rewiring everything. So, I get to the site and plug everything in and I'm ready to set levels. But wait, whats this gawd awful loud crackling noise on the transmit audio of both GE radios? Is it present on the discriminator line of the receiver? No. Is it there when the DB-9 from the radio is unplugged from the DB-9 coming from the URI? No. Now things are getting narrowed down. How about swapping URIs since there are three in the cabinet? No difference. What about swapping USB cables? No change. But wait, plug the two meter repeater in to one of the two new URIs, and it now has crackle. What!? It turns out the USB hub on the computer motherboard is oscillating! This box had 3 hubs. Moving both of the GE radios to a new hub solved the issue. I have never run across this issue before, on the twenty-something number of boxes that I have either built myself, or helped others build. I may never run across it again either, but if I do, now I'll know where to look. By the way, that noisy hub ... it works fine. I plugged the keyboard in to it and used it without any issue whatsoever.
Many thanks to KE5PTZ for tirelessly tracking this issue down, and putting up with me pulling my hair out for hours on end while doing so!
N5ZUA
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