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complaint of PCB

Johnson All Messages By This Member #25998 I cannot use my bitx for transmission. while pressing PTT the connection wire to IRF 510 burns. I think a short connection somewhere, but we couldn't identify it. Reception is OK. we have changed the Mosfet. IRF 510 is not available so we used IRF530. we tried for months on it. But cannot locate the short connection. I think it may be a problem of PCB. Think somebody would help me With regards VU3LWT
Steve Greer All Messages By This Member #26003 What version of the bitx are you using and NO the IRF530 is not a good match from what I have read there is an inbalance in capacitance.? The heat sink is not to be at ground potential it is at Positive Voltage and will short out. toggle quoted message Show quoted text On Tue, May 2, 2017 at 11:17 AM, Johnson <jv4007@...> wrote: I cannot use my bitx for transmission. while pressing PTT the connection wire to IRF 510 burns. I think a short connection somewhere, but we couldn't identify it. Reception is OK. we have changed the Mosfet. IRF 510 is not available so we used IRF530. we tried for months on it. But cannot locate the short connection. I think it may be a problem of PCB. Think somebody would help me With regards VU3LWT
Ryan Flowers All Messages By This Member #26051 One person reported that the heat sink was grounded out on the PCB and they had to fix that before the problem was solved. I suggest you check that. The schematic is available on hfsigs.com, so check the connections and start tracing the circuit between r136 and the IFR510. Best of luck to you! -- Ryan Flowers W7RLF
Johnson All Messages By This Member #26052 I first grounded the heatsink. Then i could understand my problem. Now it is not grounded. But IRF 510 is not available here. I can use only 530. what should i do? It stil burns toggle quoted message Show quoted text On Wed, May 3, 2017 at 1:02 PM, Ryan Flowers <geocrasher@...> wrote: One person reported that the heat sink was grounded out on the PCB and they had to fix that before the problem was solved. I suggest you check that. The schematic is available on , so check the connections and start tracing the circuit between r136 and the IFR510. Best of luck to you! -- Ryan Flowers W7RLF

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