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Hi,

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I believe I’ve blown one or more of my BS170’s on my low band QMX. After running FT8 into a matched antenna, the power suddenly dropped from 5W to 2W on all bands, and the current draw on receive went from about 90mA to 230mA. Double checked this on a dummy load.?

How should I test each BS170 before replacing? Since power did not go to close to 0 Watts, I wonder if not all are blown.

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73

Mike N9OHW?

I use one of the commonly available transistor testers, TC1 or similar. They are pretty cheap and will tell you if a transistor is still a transistor.

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BS170s are so cheap though that I'd probably just replace all 4 if you've blown one... it's like $0.50 worth of silicon.

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73
Andrew KI7FXL

If there’s been a problem I’d remove all the BS170s and test the gate drive signals in TX before replacing the driver IC if the signals looked wrong

Re test and then all BS170s

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otherwise you go round in circles blowing new components one by one?

Hi Mike,

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I once used ice spray on the QDX.

It clearly shows, which transistor is drawing more power than the others during receive.

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vy 73 Peter, DL4PJ?

Has anyone tried replacing the 3 BS170s with a single IR510? I have a uSDX using one that has been absolutely bulletproof. Maybe it is a unicorn, but it also gives 5 watts on 1Om. JS6TMW

Thanks all for the feedback.? I ordered 10 BS170's on Amazon and the came the next day.? I replaced all four BS170's and the rig puts out the same power as before the finals were blown, and the current consumption in RX went down to what it was before.? I was a little surprised how similar the RMS voltage readings were after the transistors were swapped.? The same down to 0.1V.? I had expected some part to part variation.??

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I tried one of the tips someone on here mentioned, to snip off the leads and seat them in a blob of solder, so as to make the next replacement job easier.? That worked to some extent, but on some of the transistors, I just removed all of the solder and remants of the old leads and did it the standard way.? If I have to go back in and replace them, I'll have two the quick way and two the standard way, and I'll assess whether the quick way helped.??

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73

Mike N9OHW

Re: How to check IC503/BS170 with DMM?

/g/QRPLabs/message/127369

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