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Post by jeremy on Nov 26, 2014 14:01:27 GMT -5
Okay, this is taking away from my Denon I planned to finally get back to after a long weekend, BUT, this is for a friend so I decided to go ahead and see if I can wrap it up quick.
Long story short, power it up, everything appears as normal until a few seconds in before the final relay click, and it goes into protection. I pulled the cover off and did some looking around, nothing blown visually on the top, or bottom. I removed CNP920 coming off the main transformer off the mainboard, and the receiver powers up and stays running.
From the schematic that connector has AC voltage on it, and 2 of the fuses coming right off that connector were blown, F912, and F913 (the lower tap of the power transformer). The voltage coming off the transformer for the lower tap is 17.5vac on both taps, which is where those fuses are. The upper taps read 45vac
Other than the 2 bad fuses, I cant find anything bad. I replaced them both, and they both blew again. So I am at a loss since I'm not a pro at reading schematics  any help is appreciated, I am hoping I can wrap this unit up rather quickly since it seems like a minor issue. |
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Post by jeremy on Nov 26, 2014 14:47:22 GMT -5
OK in IC501, STK-350-630T, Pin 7 and 8 short out, the other STK chips they do not. Also, using Pin 8 and doing continuity checks with the DMM, I get all sorts of different readings using that Pin vs the other chips. Would this be the cause of the fuses blowing?
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Post by mastertech on Nov 26, 2014 16:33:44 GMT -5
If you can hang on a little longer I will check. I'm in the middle of something.
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Post by jeremy on Nov 26, 2014 17:12:11 GMT -5
No problem, I'm not getting anywhere on this otherwise  |
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Post by mastertech on Nov 26, 2014 18:11:17 GMT -5
I looked over the prints and here is what I suggest. Remove that ic501. Once it is out set your DMM on diode scale and test for shorted legs on the following components.
Q551,Q552,Q801,Q802,Q553,Q554,Q503 and Q504.
Also check resistance of the following resistor.
R553,R567,R809 and R810.
All should be 100 ohm.
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Post by jeremy on Nov 26, 2014 18:33:28 GMT -5
Will check and get back to you, I'm actually ahead of you as I already removed that IC, so we'll see what I find
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Post by jeremy on Nov 26, 2014 18:49:05 GMT -5
Okay I checked all of those components, no shorts on any of the drivers, and all resistors read 100 ohms.
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Post by jeremy on Nov 26, 2014 18:50:07 GMT -5
For what its worth the short between pinhole 7 and pinhole 8 on the mainboard for IC501 is still there, without the STK-350 installed.
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Post by mastertech on Nov 26, 2014 19:06:28 GMT -5
For what its worth the short between pinhole 7 and pinhole 8 on the mainboard for IC501 is still there, without the STK-350 installed. Are you sure it's not pins 8 and 9? They are tied together on the board. |
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Post by jeremy on Nov 26, 2014 19:22:04 GMT -5
Nope, Pin 7 and 8, I checked, and the board does have the pins numbered
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Post by jeremy on Nov 26, 2014 19:22:38 GMT -5
I did see that pins 8 and 9 are connected on the board though and yes it shorts there as well (as it should)
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Post by mastertech on Nov 26, 2014 20:00:31 GMT -5
Go to caps C930 and C931 off of the rectifier and test across each cap both ways with DMM on diode scale and let me know what you get. Discharge first if required.
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Post by mastertech on Nov 26, 2014 20:08:16 GMT -5
I checked and yes that line is tied to gnd on the board. So all 3 will show short with the ic not installed. Maybe the ic is still good. Did you test it out of circuit?
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Post by jeremy on Nov 26, 2014 20:56:35 GMT -5
Yes I did test the IC and it is fine, Ill test those capacitors out and let you know
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Post by jeremy on Nov 26, 2014 22:49:24 GMT -5
Those capacitors read open both ways on diode scale
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any help is appreciated, I am hoping I can wrap this unit up rather quickly since it seems like a minor issue.
