Re: V6.1 Blown output transistors and pcb trace #v6 #ubitxv6-help


 

Share a pic of the power stage area on the top side.

Raj

At 15/11/2021, you wrote:
Iím having a rough time with my new V6.1 uBitX. After setting up the rig and testing receive, which seemed pretty good, it was time to check power out. I used a standard 13.8v/20a switching power supply to power the rig and a Daiwa swr/power meter and MFJ dummy load on the output. I set the keyer to straight key and used the ptt mic button to key the radio in the CW mode.

I would key the radio just long enough to see the power out on the Daiwa. I got 8 watts out on 20, 6 watts on 30, and then immediately as I pressed the ptt button on 40, I released the magic smoke. A big puff on smoke appeared from under the left edge of the main board. The pcb trace from the voltage in connector to the front panel switch blew literally off of the circuit board. HF Signals tech support said that I should have been using a 12v 3a supply and that certainly is their specifications.

So, Iíve cleaned up the board, soldered a jumper wire over the broken trace, and using a 12v, current-limited bench supply, found that the output transistors were blown. With the blown transistors removed, the radio powered up, received on air signals fine, and the raduino seems to be working ok.

Hereís my current situation, Iíve soldered in a new set of IRF510s but have not tried transmitting yet. The radio powers up fine with a little over 300ma current draw on receive. Now for my questions -

1. Iíve seen the uBitX Tuneup page on HF Signals website with the instructions for setting the PA Bias. Is there anything I should do before attempting that? Are there any other more detailed instructions?
2. I would like to check out the entire transmit chain and I see on the schematic, and the pcb, there are a number of test points available. Are there any online resources that give the expected voltages and/or waveforms at those points?

I appreciate any suggestions and comments.

73
Stan K3PW

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