need help reparing ammoon looper sudden death  [SOLVED]

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airfrankenstein
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Post by airfrankenstein »

Hello
I lent out an ammoon stereo looper (vague clone of the ehx 720) and it came back dead. I plug it in with the power supply in my studio and nothing happens, no leds light, no sign of life. I measure 9v at the power jack, and get similar voltages around the diodes and components in the attached photo. The schottky D2 seems ok : I get 9.12v on one side and 8.76v on the other, a 220R resistance one way and infinite/open the other.
diode D4 next to it reads 10 ohms resistance both ways. Is something wrong here?
Connectivity is intact across FU1, it seems to be a resettable fuse.
I did not lend it out with the power supply. The person who borrowed it is a musician familiar with pedals and told me it didn't work when he plugged it in with his 9v supply.
Any ideas where I could look or should I just presume it's dead and move on?
IMG_7326.jpg
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phatt
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Post by phatt »

I would just replace D4 and see if it comes to life.
Phil
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airfrankenstein
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Post by airfrankenstein »

phatt wrote: ↑25 Sep 2022, 01:02 I would just replace D4 and see if it comes to life.
Phil
That's what I've been thinking but I can't figure out what diode that is? Will any zener do?
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phatt
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Post by phatt »

No, it's a fair bet it's just a silicon diode used for reversed polarity protection.
D4 most likely blew because some one used a reversed plug supply. opps
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airfrankenstein
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Post by airfrankenstein »

phatt wrote: ↑26 Sep 2022, 02:48 No, it's a fair bet it's just a silicon diode used for reversed polarity protection.
D4 most likely blew because some one used a reversed plug supply. opps
ok I have some 1N914 or 1N4148.
Yes I suspect a reverse polarity issue.
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