I'm helping a friend who acquired a DIY F6. The unit was damaged in shipping. The PCP's were held in place by the FET's and no standoffs. If you never ever ship something like this, OK, but really no standoffs? Anyway, the jarring during shipping broke the pins off on three of the FET's and one board was hanging by one pin of one FET.
My friend received replacement FET's, which I installed. OK, here is the dummy move. I falsely assumed that the replacements, all marked the same as the originals, could be installed and the unit fired up. I did NOT have anything hooked up, thankfully. After a few seconds I thought I heard a faint click. I don't see or recognize any "protect circuit" so can't say why this sound. Moments later smoke. Yes I shut down immediately. I believe it was C2 on board B (rev2). That cap appears to be burnt, or the cover slightly melted. I checked the resistor (?) next to it and didn't see any damage.
I noticed that the LED on B lit up, but looking at the guide here http://www.diyaudio.com/forums/pass-labs/277850-f6-illustrated-build-guide.html I couldn't determine if the LED is supposed to light up at power up, or not. I got the impression that a lit LED is an indication of a short. But visually I could find no short or stray wire crossing anywhere.
I've since been told the Bias must be set even when like parts are replaced. The bias, P2, is easy to get to, but what direction do I turn the screw (clockwise, counter clockwise) to dial BACK the bias?
Go easy guys, I'm trying to help a friend and don't want to cause any further damage. We're in an area where there are no techs left. Nearest tech (qualified is another matter) would be a couple hundred miles away.
Thank you
My friend received replacement FET's, which I installed. OK, here is the dummy move. I falsely assumed that the replacements, all marked the same as the originals, could be installed and the unit fired up. I did NOT have anything hooked up, thankfully. After a few seconds I thought I heard a faint click. I don't see or recognize any "protect circuit" so can't say why this sound. Moments later smoke. Yes I shut down immediately. I believe it was C2 on board B (rev2). That cap appears to be burnt, or the cover slightly melted. I checked the resistor (?) next to it and didn't see any damage.
I noticed that the LED on B lit up, but looking at the guide here http://www.diyaudio.com/forums/pass-labs/277850-f6-illustrated-build-guide.html I couldn't determine if the LED is supposed to light up at power up, or not. I got the impression that a lit LED is an indication of a short. But visually I could find no short or stray wire crossing anywhere.
I've since been told the Bias must be set even when like parts are replaced. The bias, P2, is easy to get to, but what direction do I turn the screw (clockwise, counter clockwise) to dial BACK the bias?
Go easy guys, I'm trying to help a friend and don't want to cause any further damage. We're in an area where there are no techs left. Nearest tech (qualified is another matter) would be a couple hundred miles away.
Thank you
If no protection or slow start circuit are in the case, then the LEDs are on the F6 boards. The LEDs on the F6 boards do light up.
Check the solder joints at the F6 board's +/- power input did not come loose in transport as well.
Check cap polarity.
Look for burned or scorched power resistors. If they were damaged and possible changed value, maybe you are seeing a surge.
Should test the power supply for proper voltage without the F6 boards attached. Should be 23-24v.
The F6 boards are simple. Might be best to remove all components and check them off the board(s). Most of the time a DMM is enough.
Set variable resistors to minimal setting. Check F6 build guide for that info.
http://www.diyaudio.com/forums/pass-labs/277850-f6-illustrated-build-guide.html
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