In its place I now have a TE Systems 0552G. It is theoretically capable of about 350 Watts or so. I propose to use it for about 100W of data for meteor scatter, which should be an easy task. I have added two fans on transmit. It also shares two fans running continuously with my 2m linear.
I bought it second hand from a good home but it only lasted a week before failing. Not the usual bang and bad smell as with my RM VLA-150, or the broken valves and melted chokes as with the Bremi, but it just went off.
The fault turned out to be hard to find. Actually I still have not found it. It must be on the underside of the circuit board. After much deliberation I decided that the circuit board would have to stay in place. The fault is probably a dry joint or a cracked track.
So I devised a plan to bridge the fault with appropriately thin wire. This particular linear claims not to need a fuse (or so the handbook says) so I have resisted putting one in. However, as the power supply is rated at 60 Amps I do not want to find that the underlying fault is a burned out track. So the bridge is lightly made to fail if that does happen to be the problem.
I still had doubts about this plan and so I consulted my friend and mentor, Bob, G3KML. Bob came round to see the problem. First we spent half an hour while I explained that the circuit diagram in the 0552G manual (and on the internet) is wrong. If I believed the circuit diagram then this fault is impossible, as no voltage was reaching the switch board, but the PAs were live. According to the diagram such a situation cannot happen.
Bob also thought that taking out the board would be a mistake. He thought that my plan should work. We did a few tests to prove it. I took a few days to think about it and decided to bridge the hidden fault (wherever it is on the circuit board) with a simple wire.
The wire is routed round the outside of the board. I made a mistake with the point chosen to solder in the bridge and that has resulted in the switches on the linear not quite working in the right manner. I will fix this some other time, the point is that the machine is restored to operation.
|The TE Systems 0552G with my bridge in place|