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Old 09-10-2020, 11:57 PM   #29
SolomonMan
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Join Date: Apr 2019
City & State: Deshler,Ohio
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Posts: 148
Default Re: DC Power Supply QW-MS605D

Quote:
Originally Posted by pc7fan View Post
I have an MS605D here. Replace the P75NF75 FET and that should fix the cap popping and cycling issue (use 100V output caps instead of the 63V ones).
Back at it again....

So I got the KA7500B ICs and the other day I decided to plug it back in and see where I left off with this project. Before bringing out the soldering gun.

With all the knobs turned down to minimum I turned the PSU on.

For about 3-5 seconds it did the cycling/revolving as shown in the video I previous posted.

Then there was a flash near the T2 Transformer. (I was reaching for the plug anyways when this occured to turn it off)

It was not a large flash by any means but enough to be visible. Then the cycling stopped and the PSU is reading 0.00 on both the Amps and Volts.

Upon trying to set the Voltage there is no increase. (Steady 0.00 until you get the Voltage knobs to max and the Amps show 0.02)

So I got out the magnifier and I do not see anything out of the ordinary in the sector of the board.

So I am going to go forward with the KA7500B IC swap.

Please bear with me (not been doing electronics repair recently except some Remove & Replace)

When I test the P75NF75 FET. I assume its best to get it out of the board.

Test (1)
Pin 1 to 2 or Pin 1 to 3 should not have continuity (be shorted).

Test (2)
Pin 3 (Multimeter Red Lead) to 2 (Black) should have continuity (shorted).

Test (3)
Reverse Leads should not have continuity.

Below is mouser datasheet for reference.
https://www.mouser.com/datasheet/2/3...71-1795852.pdf

Thanks in advance,
Chris
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