I haven't had a faulty CMU200 supply but have repaired many HP 8924 & E8285A supplies. I had put aside an E8285A supply for a couple of years because it got the better of me until a ham radio contact told me to read this http://www.repairfaq.org/sam/smpsfaq.htm - It didn't specifically help fix the supply but put my mind into SMPSU repair mode which enabled me to nut it out. I also have read somewhere that CMU200 supplies also fail from dry electrolytic's & opern circuit inductor.
73s om de chris zl1cvd
Hello Rich
today I opened my CRTU which I guess has the same PS (PULS SN250) and 'probably' the same connectors at the control side. I believe at least the former is true, so here's what I did:
1) check voltages at PSU connector with unit turned OFF (but powered)
2) check voltages at PSU connector with unit turned ON
3) identify possible "power on" lines at PSU connector
3) turn off and disconnect unit, find those 'candidate' lines at control side (X12 connector in my unit)
See attached pictures and PDF. Pins pictured in green, output some voltage even in the OFF state.
So, I'd say B1, C1 and D1 are pretty good candidates, especially B1 given that the ON logic could be negative.
If i were you I'd measure the voltage at B1 with the PSU disconnected from the equipment, and if you get some voltage, drive it to zero with a
10K to 100Kohm resistor
I think you missed the PDF I posted earlier. there are the voltages at standbby and power on.
from what i see your unit looks good in standby state. Can you look into the logical circuitry inside the PC that drives the signals I refer to in the X12 coonector? If at least we knew if those signals are inputs or outputs to,the psu
Good news, just decided to test the B1 pin by myself. While the CRTU was in standby I drove that line low with an 820ohm resistor (just to go a bit farther than you...) using the grounded screw next to it and voila it turns on
I was confident about B1 because the 0.2V present when the unit is on, resembles the saturation voltage of a transistor driving that line low.
So next thing you'll have to test the same, and you'll know if its the PSU or the control unit
Cheers
Was yours on the bench unloaded or in circuit when you did the test??
Was yours on the bench unloaded or in circuit when you did the test??
It was inside the crtu, it may have another signals that need to be connected before power up.... so all is not lost for you
Theres one more test you should do. put a scope probe at b21 and see whether the line is driven low by pressing the power up button or not. I suspect it will, and you have a faulty PSU.
I recall from another eevblog thread about the cmu or crtu ( cant remember) that a guy fixed his psu by changing a switched regulator. It was something like TOP2000Y or TOPY2000, at the time I looked at ebay and it was available for sale. Besides trying to 'debug' that psu Id suggest you change that chip too....
Keep it up, that unit deserves to be repaired!
EDIT: it was a TOP200YN...let me know if you identify that part in your unit
At this point all you have to do is find the faulty item within the PSU , otherwise the signals look ok. If I were you I'd find a substitute TOP200YN...Meanwhile keep looking and see whether you can test and identify any other broken parts
Yes, c1 d1 are probably power good outputs, and maybe a1 too
The direct replacement, with only a tiny difference from the original is the 3 pin top222yn available from Mouser:
Very interesting discussion
A trick I also used with a CMU to power it on is to keep the power on button pressed during switching the power on on the back of the CMU. After doing this sevaral times I got the CMU to work again in some instances. Mine also started with green light but stopped during booting to shut down.
I'm also wondering which part of the controller is powered on during standby mode to detect an activated power button. Is there a watchdog sort of reset circuit on the controller which drives the activation pin of the PSU, or is the button directly wirded to the activate PSU pin without any intelligence?
I hope your PSU is still alive.
Just found out :
B1 (activation) on X110 is connected to B24 on X12 (the main connector to the front unit)
next step is to see where that ends up on the board
Indeed it's also mentioned on your sheet, didn't noticed it before, I thought I had a break through
I did some more testing, but using another PSU, without front panel attached
Good PSU :
With power switch on the back on the standby led is constantly green
starts up after B1 to GND
Bad PSU
With power switch on the back on, the standby led is going down after few seconds,
Does nothing with B1 to GND
With (probably bad) front panel attached:
Good power supply with B1 to GND doesn't start up,
The latest thing could be of interest for topic starter:
Does it make any difference if you attach the front panel with respect to the activation of your PSU?
Unfortunatly I don't have a poven good spare front unit... (though some good CMU's but dont want to break the seal.
Nice job Rich, eventually youll get the faulty part. Dont forget to post your notes on the psu (ie part numbers, schematics...) as it may help others in the future!