BS170's get very hot in receive mode

[AntonR]

Hi,

I finished my (tr)uSDX and installed the firmware. Selecting bands is working. But after powering with USB I notice that the BS170 are getting hot already in receive mode.

What can be the problem?

Thanks for your help!

Regards,
Anton

[DL2MAN]

BS170´s dead or soldered in reversed.
There are BS170s with wrong pin outs. Even the datasheets contradict each other.
Exchange BS170s and watch for right pin order.

73 Manuel; DL2MAN

[AntonR]

Thanks Manuel,

I ordered a batch of BS170's, will swap them this weekend.

73,
Anton

[AntonR]

Dumb question; I removed the BS170’s, before replacing them one check; can I receive without those FET’s?

73,
Anton

[DL2MAN]

Yes

[AntonR]

Thanks! Replaced the FET’s, not hot this time. But still no reception, same noise with or without RF board. Sending on USB power states power 0.24W and a SWR of 9.99. The first is to be expected, the last is the next thing to fix. I will use a signal generator and follow the signal from the antenna port with my oscilloscope further along the board.

73,Anton

[AntonR]

Reception is OK now, replaced the T1/T2, (2/14). Still low power TX. Replaced the 3 BS170 again,
no results. Removed them, I measure ~2.45V DC on Gate, 12.6V Drain. Is this oké?

Placed another first BS170, power on; "Fireworks".

Up to the next batch of FET's..

[AntonR]

After buying a component tester I found 1 explanation of the problem; my complete stock of BS170’s are fakes. (Not those 3 from the kit, I broke them due to a short)

https://twitter.com/antonrietveld/statu ... 8TSUC4iHww

I have to order somewhere the real thing

73,Anton

[AntonR]

Yes! Finally got it working, FET’s from QRP Labs; first QSO yesterday with End-Fed ~1000KM to Slovenia on 20 mtr. Today efficiency check: 4,76W 88,46% eff. on 40 mtr. on End-Fed

Manuel Thanks!

Anton - PD5ANT, 73