DBdrive SPEC equalizer - failure mode - diyAudio
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Old 16th June 2012, 02:14 AM   #1
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Default DBdrive SPEC equalizer - failure mode

Just a note for folks who have these. There's a zener diode in the power input that can blow and burn through the plastic sheet insulation under the circuit board, shorting to the chassis. I'm pretty sure the guy connected it backward for it to blow as badly as it did. The symptom was low frequency oscillation in the amps, and measurable voltage between the shields of the RCA jacks and the chassis. The diode is tacked across the ground and bat+ inputs right behind the connector; it is not part if the PCB, so it sticks out enough that when it blows, it can touch the chassis once the plastic insulator melts. I would have thought it was an isolated incident until the client mentioned that he knows a couple of other people that have had similar problems with them. No pic, sorry, wife had camera...
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Old 16th June 2012, 07:10 AM   #2
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If it's directly connected across the B+ and ground terminals, it's likely a standard rectifier diode. They only fail when connected to the power source with reverse polarity. This is a generalization that applies to most electronic components designed for operation from a DC supply.
Low frequency oscillation is more commonly due to an open shield ground either in the EQ or the head unit.
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Old 20th June 2012, 01:56 PM   #3
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I was just thinking last night that I should edit this post to reflect that, but you got to it before I did... I guess the diode is meant to blow the fuse by providing a short when its hooked up backwards right? Of course, that only works if you fuse the unit... I reworked all the usual solder joints (rca's, pots, TO-devices, etc) (and replaced the power connector with a pigtail per request...) and its much better.
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