Here is the problem, I got a 1x4 mobile amp that I got from a guy who burnt some resistors and the transistor on the very right of the 4 pill section, he took the amp to a local amp builder who fixed the burnt transistor. Then the original owner then hooked it back up and burnt the same transistor and a few resistors. I the bought the amp for cheap and fixed the resistors and put a new transistor. Then i put the amp on my test bench and its getting full output, but the new transistor gets hot fast?? so I turned it off to not burn up any more parts. Need help as to why this transistor gets hot and how to fix the problem. (SWR) if fine. Thanks.
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1x4
- Thread starter Number15
- Start date
It could be for a number of reasons, the transistors may be mismatched and if this is the case you should notice the balance resistor on the back of the output transformers getting hot or discolored .
But the most likely reason may be either the guy did not use heat sink compound when replacing the transistor or he may of not gotten the new transistor seated properly which would cause it to get hot because it has little or no contact with the heat sink.
Look at the new transistor and see if it's not level to the other transistor next to it.
Got any pictures?
Yes the balance risistor was burnt, and replace with a 100 ohm 5w the old one was 100 ohm 2w and I will check to see if it has heat sink compound and seated properly.
Hard to tell by the pictures but is the pill to the far right down flush to the heat sink like the other three? you might have a look at that or lift the pill to see if it has compound under it.
From what I'm seeing everything else looks ok.
From what I'm seeing everything else looks ok.
Yes I just did that, I added compound and its sitting flat like the other pills. but gets hot in seconds. ?
Not for long, another reason they get hot is if they've been over tightened and do not sit flush to the heat sink, you can remove the pill in question and lay it on a known flat surface (a pane of glass) and you'll see the deformity.
But if the pill is noticeably that hot and has full output you should check that but it won't last forever getting that hot.
If you find it has been over tightened you can lap it back flat by wrapping a small pane of glass with a fine grit sandpaper and sand it back flat.
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