PA-100D Fan always on?

[JK1QLQ]

Adrian

Latest update. roWaves contacted me Friday morning with some thoughts.

1. They believe the power button problem may be Q1, Q2 and Q4 MOSFET damaged. Either from current spike or electrostatic.
2. They also think that no amplification and 0C displayed could be related for #1 above, or poor connection on the ribbon cables.
3. They asked me to perform a similar test to your recommendation with the PTT cable T/R short to see if the unit would go into TX mode.

I checked & cleaned all 8 ribbon connectors (all appears in good condition), and repeated the PTT cable test. In both cases there was no change to the units performance.

As I am unable to safely perform SMD component replacement of the MOSFET's they identified, I told them it only makes sense to return the unit for either repair or replacement under warranty.

I'm a little surprised they never asked more about the fan operating in Normal mode at low temperature when I first used the unit and functioning properly.

I did not hear back from them again Friday, so will have to wait until next week for further response (they do not respond on weekends).

73
Scott JK1QLQ

[5B4AIY]

And there I was, hoping that a hard reset would fix things! Apologies for the late reply, I've been rather busy with other things.

If you examine the Control Board schematic, you will see that when you press SW7 you apply a +ve voltage to the gate of Q1 via one of the diodes of D1, which causes it to turn on, and thereby turn on Q2 and Q4. Since the microprocessor powers up, this means that Q1 and Q2 at least turn on, and that the PWR-ON latch signal is present and holding the power circuitry ON. If Q4 has failed, then this would mean that there is no auxiliary +12V, and this bus powers the T/R logic, temperature sense and bias logic, and fans, which would account for the majority of your problems. A quick check with a multimeter on the +V bus at C2 would identify this failure.

If you cannot power up by means of SW7, then can you power OFF by this switch? SW7 is sensed at pin 58 of the microprocessor for other purposes, so if you can power it off, as well as perform the secondary switch functions, then this would suggest that one of the diodes of D1, the BAV70, is not working or has a poor soldered joint.

If Rowaves cannot help, then we might have to do some open-heart surgery. Fortunately replacing components in the area of Q1/Q2/Q4 is not too difficult.

Let me know what happens.

73, Adrian, 5B4AIY

[JK1QLQ]

Adrian

Please do not apologize. Your assistance is very kind and greatly appreciated.

I'm still awaiting a response from roWaves, but will let you know when I find out. [UPDATE: roWaves just contacted me and is preparing return shipment documents for repair/replace]

Thanks & 73
Scott JK1QLQ