Tuesday, 21 June 2016

Six meters - repairs to my TE Systems 0552G linear.

My old Bremi valve linear - the one we converted, blew up, and re-converted - has been retired again. It was too much of a beast, too flaky. It needed even more work done on it and I have had to admit that I have run out of patience with it.

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
So my jinx with 6 metre linears goes on. At least this one has been restored to health for now.

73
Jim
GM4FVM

3 comments:

  1. I OWNED ONE FROM 1998 IN kl7 TOOK IT TO DXPEDTIION vk9 IN 2003 NEVER HAD AN ISSUE WORKED 47 COUNTRIES AND 2000 QSOS, YOU ARE STIFF OR YOU OVER DROVE IT.

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  2. Thanks for your contribution.

    Well as you can see the fault is in the PTT circuit, so I do not think I overdrove that. When I buy second hand (used) items I do not expect everything to work perfectly. A broken track or a bad joint after years of use is not really the fault of anyone.

    So if I did not overdrive it, I must be stiff then? I see.

    It is a very good linear which I am still using. I would recommend it to anyone.

    73
    Jim
    GM4FVM

    ReplyDelete
  3. Hi Jim, Well done I'm the stiffed one I got one in from USA based on my previous experience and it is a dudd. SO excuse my petulant prose. I am trying to get assistance and find it lacking.

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