Another TTX2 Motherboard Repair

[herr-g]

Hi,

I wanted to share an issue with a TTX2 motherboard:

Symptom:
Random system reboots, sometimes not starting at all. After one day with those issues, the TTX2 won't seem to start anymore at all. Powers on, but nothing more.
With a POST diagnostic card, I could see that all Power Supply voltages were present (3,3V, 5V, 12V) but nothing was initializing at all. So typically either an issue with CPU, BIOS or Power Supply.

Further diagnostics:

• CMOS Reset => no change
• CPU swapped => no change
• Checked the voltages on the CPU MOSFETs: Only one of the four power stages delivered a proper output (drain) voltage. => Issue with the CPU power regulation.
  • Checked the MOSFET circuits for shortages => no issue found
  • With a scope I could see some of the MOSFETs pulsing, but not regulating to a proper voltage. => Obviously a PWM issue.
  • Checked all resistors and diodes around the buck converter circuits => no issue found.
  • Replaced the PWM buck converter ISL6312 CRZ => Problem solved

Repair notes:

• This repair requires expert SMD soldering skills and proper equipment. Always apply good flux before soldering and only a little solder tin.
• The motherboard needs a lot of steady heat for the solder to get molten. And the buck converter has a big grounding plate on the bottom, so it needed easily 5 mins at 340°C with the hot air gun before I could carefully remove the part.
• The replacement part has to be aligned with a hot air gun so the grounding plate can be affixed exactly in position. After that apply flux around the contact rows and carefully drag-solder the IC. Double-check for possible shortages with microscope and multimeter.

 

[channelmaniac]

Nice fix!

 

[herr-g]

@mods: Can someone move this thread to the Type X subforum?