Today was a day of the unanticipated !
When the morning broadcasts ended, we decided to remove the capacitor that we put in TX3 on Saturday to analyze what had failed and to be able to explain the reason for the symptoms that we had seen. Lo and behold, everything was working properly with none of the symptom we had observed for several previous days! We looked all over for possible bad connections, but found none. This left us uneasy about the possibility of the return of the problem. Since the operator on duty is not allowed to open any doors or panels without another person on site, we left a capacitor inside the cabinet with two clip leads at ground potential extending outside. If the problem reoccurs, the operator has been instructed to connect the two leads together, thus connecting the spare capacitor into the circuit.
Next, we had noticed that one of the door interlock lights on TX1 was on dim. When the problem door was checked, it was discovered that the interlock switch was not working. Opening the interlock switch enclosure, it was noticed that one of the connections was corroded as if it had been wet. The switch and some of the corroded wiring was replaced. Everything tested OK.
Just as the repair was being completed, Graham felt a drop of water hit his head. Our next detective work was to find out where the drop was coming from. Looking from the top provided no clue. Next, several air filters were removed to allow gain access from the side. A puddle of water was seen on the top plate of the transmitter and Graham was able, with the light from a ‘torch’ [flashlight], to see that the threaded pipe into the bottom of the heat exchanger [large radiator] was leaking. Because of air ducting that has been installed on site for cooling, it was necessary to remove all the back doors of the transmitter and the top trim to gain access to that area for repair. The threaded pipe was not very tight, so we removed it, renewed the Teflon tape on the treads and retightened the pipe, then put everything back together.
In the process of checking out the door interlock light problem, it was noticed that the ‘ground switch down’ light was not working on TX2. The grounding disc was contacting the bleed resistor but not dropping far enough to contact the ground contact. The spring on the grounding disc was too hefty, so we located a replacement, but this required some modification. With a little work, using the lathe and modifying a washer, it was possible to make it work correctly.
While this was being done, I noticed that the optical arc detector light was not on. Since it is sensitive to light, it should come on when the door is open. After using several drawings to assist in tracing the wiring , it was found that this detector should have been connected in parallel with a second detector (from the same area) on a terminal block behind the control panel. When the connection was made, everything worked as it should.
After this discovery, the other two transmitters were checked out. TX1 was OK, but TX3 had the same problem. This was also corrected. I could not determine whether this was left out when the transmitter was assembled in Elkhart, or was removed after it was installed here.
It was also discovered that the ‘ground switch down’ indicator light was not functioning on TX3, while the switch was actually down. It looks like the limit switch needs to be adjusted — a job that will have to wait until tomorrow.
TX2 came up for the evening broadcast with no problem, but I did notice that the calibration of the RF drive controller needs to be checked. This will, also, have to wait as multiple bands will have to be part of that calibration. TX1 should also be checked out. TX3 has already been done.
Just before leaving the site, TX2 was manually switched on about 10 minutes early for its second transmission, just to make sure the problem from Saturday had not reappeared. All was OK.
After I left for work this morning, Virginia learned that we would be having a family over for dinner this evening. Greg and Ingrid, and their two young children are here for a week. Greg had been in Bratislava and in Swaziland at the same time Allan and Joyce were in these places, but Greg was single then. He is here from TWR’s Africa Regional Office in South Africa to work on the security system in the Manzini office. Ingrid and children came along, since they are on vacation from school.