First Generation TIU, Dead Variable 1 Channel, New FET's and Still Dead

Dave ZucalOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

I'm planning on building a new layout, which I want to power passively with an old first generation TIU I bought for a reasonable price, because of two dead channels. First thing I did was upgraded it to 6.1 then tested each channel. Fixed 1 was popping the brick's breaker, caused by an open TVS, which I replaced and is now working fine. Fixed 2 and Variable 2 tested good, but Variable 1 was stone dead in both fixed and variable mode. I tried a factory reset, still dead. I checked the TVS, good, no continuity. So I assumed a bad FET. After removing all four, I diode tested them and to my surprise, they were all good. So I replaced them anyway and still have a dead channel. No other components or traces look to be burnt. Is it possible something happened to that channel during the upgrade? This TIU still had it's original program so when I upgraded it, I did it in two steps, 5.0 then 6.1 and did a factory reset after each. Has anyone ever experienced losing a channel after an upgrade?

2/25/218:19 AM

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Alan MancusOGR Forum Member DIGITAL SUBSCRIBER

you stated tvs diode incorrectly an open diode will NOT TRIP THE BREAKER. did you mean to say a Shorted tvs diode tripped the breaker so you replace it ? the tiu can be repaired and should not be to expensive if you would like i can repair it! what REV is your tiu ?

Alan

2/25/219:46 AM

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Dave ZucalOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Alan, The TVS on Channel Fixed 1 was allowing current to pass through, from one power lead to the other, which I thought to call open. My mistake. The TVS was shorted. Any thoughts on my Variable 1?

2/25/2111:08 AM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Dave, the trace that gets cooked on the Rev. G (original) TIU is on the bottom of the PCB. If you look there and see an embedded trace that's cooked, it's last rites for that board, there is no fix for that. Since the Rev. G had no fuses, and the trace wasn't sufficient to carry the required current, it's not uncommon to see this failure, I have two of them in my closet that have met that fate.

2/25/2112:06 PM

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Dave ZucalOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Thanks John, here's a photo of the board bottom I took just before soldering the new FETs in. Would the trace I'm looking for be on the left half of the board? Variable 1 is to the left.