UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
romPost: MPC106 Walking-one passed.
romPost: MPC106 configuration passed.
romPost: First PCI access passed.
romPost: PC87560 Walking-one passed.
romPost: PC87560 configuration passed.
romPost: DEC21554 configuration passed.
romPost: PERFORMING ROM CHECKSUM TEST...
romPost: ROM checksum passed.
romPost: PERFORMING DRAM CELL TEST...
romPost: Enabling data cache...
romPost: Data cache enabled.
romPost: Enabling instruction cache...
romPost: Instruction cache enabled.
romPost: DRAM Cell test passed.
romPost: Disabling data Cache...
romPost: Data cache disabled.
romPost: Disabling instruction cache...
romPost: Instruction cache disabled.
romPost: PERFORMING DRAM MARCH TEST WITH CACHE OFF...
romPost: Writing address to each *address...
romPost: Reading address from each *address...
romPost: DRAM march test passed...
romPost: PERFORMING DRAM MARCH TEST WITH CACHE ON...
romPost: Enabling data cache...
romPost: Data cache enabled.
romPost: Enabling instruction cache...
romPost: Instruction cache enabled.
romPost: Writing address to each *address...
romPost: Reading address from each *address...
romPost: DRAM march test passed...
romPost: PERFORMING DRAM WALKING-ONE TEST...
romPost: DRAM Walking-one test passed.
romPost: PERFORMING NV-MEMORY WALKING-ONE TEST...
romPost: NV-MEMORY Walking-one test passed.
romPost: Disabling data Cache...
romPost: Data cache disabled.
romPost: Disabling instruction cache...
romPost: Instruction cache disabled.
romPost: Enabling instruction cache...
romPost: Instruction cache enabled.
romPost: POWER-UP DIAGNOSTIC COMPLETE.
Hel
VxWorks System Boot
Copyright 1984-1996 Wind River Systems, Inc.
CPU: Tektronix HPP - PowerPC 740
Version: 5.3.1
BSP version: 1.0.8.0
Creation date: Jun 27 2003, 09:52:32
Press any key to stop auto-boot...
1
0
auto-booting...
boot device : sm
processor number : 0
file name : c:/vxboot/vxWorks.st
inet on backplane (b): 192.168.0.1:ffffff00
host inet (h) : 192.168.0.2
gateway inet (g) : 192.168.0.1
flags (f) : 0x1008
target name (tn) : tds7000
startup script (s) : c:/vxboot/topscript.hw
Initializing backplane net with anchor at 0x1e80000... done.
Backplane anchor at 0x1e80000... Attaching network interface sm0... done
Thank you for the photo. Unfortunately, tds7104 can only be changed to TDS7404 by radical replacement of the acquisition board and casing. You can specify the values of the following resistors from the photo:
R781, R791, R782, R792, R783, R793, R784, R794.
Conceptual question: Why is there a high and a low side switch (driven with solated gate drive), while only a low side switch would be good enough and do exactly the same?
Hi again,
I tested now:
Body diodes of the IRFP460 (not IRFP640 as I wrote in the PDF)
- present as expected :-)
- RDS(ON) of Q10 is 0.23Ohm and it turns off as expected
- RDS(ON) of Q9 is 0.235Ohm and also that one turns off as expected
Furthermore, I tested the voltage limiting circuit with the 2 18V zener diodes. Also here I see, that it limits correctly to roughly 18.8V. I tested this in both directions to ensure, that both the zener diodes work as expected.
I measured (CR80/81) and also they properly conduct only in one direction and show very low Vf as expected.
I right now now injected 30V into the Fuse (Fuse removed) and also injected the 18V externally.
The UC3844 oscillator still oscillates and the ISense pin still shows the same huge voltage transient. So far so good.
Unfortunately I have killed the NPN transistor FMMT720 of the isolated gate drive transformer driving circuit due to a measurement mistake.
Reichelt order is out, too tired now to replace it with another transistor from a different section of the power supply.
What I think I had seen is, that the amplitude of the transformer (T52), that drives the gates was for one of the final stage FETs about only half as high as for the other ones. Unfortunately seconds after this, I killed the above mentioned transistor.
I will check further tomorrow. Learned a lot today in terms of SMPS testing metothology today, thanks for your hints.
Getting a bit afraid, that the actual transformer T7 is killed. This would likely be the killer criteria and the way forward for me to replace the full power supply. I expect this is a custom made transformer, that is not available off the shelf.
Next steps for me:
- Replace the Gate drive FMMT720 transistor.
- Check, if my observations with the different voltage amplitudes for the 2 final stage FETS is correct.
- Maybe replace the primary side coil from the transformer with a resistor and measure ISense again?
- Continue investigations on the secondary side (but could that kill components on the primary side? Based on the schematic I can first decouple the 15V path, to check, if there is a short present
Best regards,
Kai
PS: Attached how it looks like now. Need to remove a lot of flux at the end, but well, lot's of cables. NICE :-)