Re: Fender Blues Junior IV guitar amp not working

A very very hot EL84 suggests the negative bias (pin2) is intermittent or not present. One of the two power tubes out of bias would cause tremendous hum sound. Either the ribbon cable supplying the negative bias voltage has a bad solder connection to either the main board or to the poweramp board, or the tube socket on pin 2 of the hot EL84 has a sloppy connection to the tube. First try re-tensioning pin 2 on the hot EL84 socket. Of course be sure all power is disconnected. You can do this with a jewelers screwdriver or similar tool....

Re: 2019 macbook a2141 backlight troubleshooting

Tried the onboard pwr button (actually these was no switch, just two pads) to no avail. I cannot seem to get the logic board to boot on the bench. If anyone has successfully booted an a2141 logic board out of the case please let me know the setup. Maybe I should have done an NVRAM reset and/or SMC reset before disconnecting the board (?). Although without a battery connection it seems the NVRAM would reset on pwr up.

Re: 2019 macbook a2141 backlight troubleshooting

Thank you! I had not seen these!

Re: 2019 macbook a2141 backlight troubleshooting

Further information - I do not have PPVOUT_S0_LCDBKLT voltage - should read 59V, I read 0V. Also do not have EDP_BKLT_EN. And furthermore, BKLT_SD reads 12.5V (should read 0V to turn on Q8400 to pass 12.6V to backlight boost).

Re: 2019 macbook a2141 backlight troubleshooting

Hi mon2, I didn't see an attachment. I did not realize there were surface-mounted pushbuttons on the logic board. I will look for them. This could help me greatly. I don't know if the keyboard backlight is working because it may have been disabled. I received this macbook not working. Thank you!

Hello, I have a 2019 macbook a2141 with no backlight. video image is visible with flashlight but no backlight. All the associated circuitry is located on the back side of the logic board. I've removed the logic board and display and have them connected together on the bench so I can probe the back side of the board. I'm applying power through a usb-c port attached to the logic board but I'm not sure how to actually boot the logic board. I tried attaching the power button and that didn't work. I also have the fans attached and they are not spinning. If anyone can help me with this setup I would...

Re: New Members - please post your introductions here

Decided to join this excellent forum while trying to revive a 2019 Macbook Pro and looking for info on openboardview and associated files. I am a retired EE. Last job was as a test and verification engineer for Xilinx. Since then I've been self-employed repairing guitars and guitar amps. I also started collecting and repairing Tektronix scopes and calibration gear as a side interest.

I look forward to having access to all the knowledge available here and hope that I can contribute to the community as well. I'm...