Troubleshooting a headend system

[Matt Stealey]

Over the last week or so I have been troubleshooting a 50 channel Directv hotel analog headend system that is using Cabletronix mini mods. Model CT-FMM. when initialy arriving on site an entire Chassis for channels 36-49 were no longer displaying a picture. only displaying a black screen. The power supply and all mods were receiving power as indicated by the led on the front panel.

When replacing the power supply half of them came back up. So then I replaced those mods with some blonder tongues I had laying around thinking the mods were out. The new mods restored those channels but knocked out 5 others. That has happened multiple times and it is happening on both the cabletronix mods and the blonder tongue mods. Not always the same mods but within same issue, replace a few mods, they come on and others go out. I also have an issue with the power supply shutting down everytime I begin connecting the wiring harness to the mods or if mods rub touch the power goes out. As of now I have replaced nearly everything except the amp and receivers.

I am new to headends and have only done 3 hotels. All within the last 6 months. Any help would be appreciative.

 

[bweiteka]

Wow! Sounds like a mess. The power issue is strange...does it only happen on the bank of mods for channels 36-49? Or does the power go out in the whole room? Are you using a meter to balance the system or just going off of picture quality? Given the power and channel issue, make sure the system is disconnected from the launch amp, and thereby electrically isolated from the rest of the tv's in the building, to test. Is the rack grounded? Is the troublesome row of mods on its own power strip, like each row of mods has its own power strip? It almost sounds like stray voltage wreaking havoc somehow...have you checked for voltage with a multimeter between the mods and ground or between the building side launch cable and ground? Lots of rambling questions, wish I was there lol. Does the mod send picture when connected directly to a tv rather than the combiner?

 

[Claude Greiner]

Sounds like a possible grounding issue.

I try to stay away from analog systems these days