Repairing eBay eb832

[Miker79]

I purchased an eb832 sold as not working but communicating with head unit. Simple fix right? No. When I opened it up I could tell someone had already tried to repair it, poorly.
I swapped out the caps on the 120ac to 12v supply but the voltage is jumping around from 8-30v dc. I ordered a new one 12v supply. The second issue is when I checked the aquabus I’m getting 19v dc. It looks like the previous owner had tried to swap the 33063 chip and cooked the area. I swapped out his chip for one of my own but I’m still getting 19v dc. Any thoughts on what can be causing this? I don’t want to attach it to a head unit until the voltage is in a more reasonable range.

 

[SuncrestReef]

@_AV would be the one to ask.

 

[_AV]

Voltage fluctuations on the 12v PSU does mean something else is wrong with it. Replacing the entire PSU (AND upgrading caps on it) is the right move.
18-19V on AquaBus is not unheard of. Although, it's a little high indeed. Remember that they are using a buck converter to generate it and not a proper power supply as they used to in old EB8 models. A scope would tell you if power fluctuations generated by the buck converter are too high and if they are not being smoothed out by the filters on the output. While higher voltage like this is not necessarily critical, because consumers regulate it anyway, unfiltered output may be a bigger problem.

Also, when I'm working in that area, I always test my work with a variable load to ensure correct outputs once the repair is complete. This tells me if the output voltage under load is reasonable and that it can handle the load as expected. Here, for example, I'm seeing 14v output before the load is applied:

 

[Miker79]

I don’t currently have a variable load tester to test the output. Or a scope to view the signal. I checked a couple of different eb832’s and they showed 11.8-14v. It sounds like 19v won’t hurt anything?
Is there another way to to check it out? Or a reasonable priced load tester you would recommend?

 

[Miker79]

I found this relatively cheap on Amazon they jump up fairly quickly to over $200 with a few in the $50 range. Would this work as a aquabus load tester?

 

[_AV]

Just curious. Is this the EB832 that was sold last weekend on ebay for around 165 plus shipping from TX? ouch...
I was watching it but never bid as the price quickly gone wild on the last day.

Anyway, I would stay away from those cheap loads. They will work fine at higher loads, but fine tuning at lows is going to be a problem. Especially since aquabus can't support much of a load anyway. Instead, I'd use a small 12v fan. Just make sure that it doesn't draw more than half an Amp.

19v by itself is not that big of a deal. The problem is that you don't know if the reason it's this high is because it's the raw unfiltered output from the buck converter. 19v can be easily regulated on the other and down to whatever is needed. But electronics doesn't like the power to fluctuate unfiltered. The frequency is much higher than what your regular multimeter can detect, but for sensitive components it's a problem.
You can just go ahead and replace everything in the filtering circuit and see if it fixes the problem. Otherwise, you'd need a scope to test and verify.

 

[Miker79]

Yup from the description it sounded like an easy fix on a nice looking unit. Once I get the 12v supply replaced I’ll hit you up on your website hopefully you can find the issue. This is outside my skill to diagnose.

 

[Miker79]

Took your suggestion and hooked up a fan as a load. The voltage dropped from 19v to 10.9 @ 77.5 mA still have no idea as to the quality of the output but the voltage is in a good range

 

[_AV]

yeah, that's a significant drop under load. And another indication something is wrong around the converter. Since you already replaced the buck converter, I'm suspecting the filter circuit... perhaps the inductor melted or the cap. There is a reason it's showing 19v while others stay at 14 w/o load.