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DIY DC8 repair


armydoc

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I have a DC8 with two always on outlets (5&6). I've tried to reset the controller and manually change he outlet state with a table lamp hooked in but still always on. I found this thread and ws wondering if anyone local had tried it. Unfortunately the thread doesn't give me any direct specs for the triacs and Curt at Neptune said he couldn't supply them or provide part numbers for liability reasons. I was hoping some one here knew the exact triacs to order.

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I've not done this, but the triac that he removed and the third one from the left in the pictures that you linked to is a BTA12-600BW. That's a 12A triac. It looks like he's replacing two of the bad ones (the two to the left of the one I referenced above) with a BTA24 - a 25A triac.

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Ok. So based on very basic Triac knowledge gathered from google the difference between the "stock" triac and the one installed was the on-state RMS current. My interpretation is as follows and please someone correct me because there is no way I got this right:

In normal operation, the pump received a gate voltage and thus current signal from the controller and the pump turns on from the 120AC voltage. When the pump current goes above and stays above the on-state RMS current the circuit is closed and stays closed. Then, another signal is received from the controller and the pump current must drop below the on-state RMS for the switch to open.

I guess the stock triac requires the device to maintain a lower current to stay closed.

The question:

Is the BTA24 an improvement to the DC8 or just the part that was available at the time?

Attached is a comparison sheet from mouser.com.

Mouser Electronics - Compare Products.pdf

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I suspect that the 12A triac was selected by the designers of the DC8 for two reasons: One, it is rated lower than the 15 amp socket that it connects to and, two, it probably costs a little less. Insofar as performance is concerned, the BTA24's increased hold current (75 mA vs 50 mA) is of minimal impact in this application. The BTA24's increased current carrying capacity, though, probably results in greater tolerance to surge currents (which probably caused the component failure in the DC8 that you have now). Consequently, it may be more reliable though it leaves you open to pushing more current through the socket than the socket is rated for.

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Thanks for your insight. BTA24's ordered. Wish me luck.

Holding beer and watching this. At least you probably won't be plugging in a >15A device into this outlet for use on a nano tank!

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Holding beer and watching this. At least you probably won't be plugging in a >15A device into this outlet for use on a nano tank!

I don't recall if the entire DC8 is fused or not. If it is, you shouldn't easily be able to overstress the outlet. I can't say, however, what other internal wiring or PWB traces are rated for.

 

I'm glad that you posted this, though. I had one triac go bad on me a couple of years ago. Luckily, the DC8 was still under warranty, so I just had Neptune take care of it. However, I know that several people here have DC8's with at least one bad outlet. This should help them because, as I recall, this is the most common type of failure for this accessory.

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Holding beer and watching this. At least you probably won't be plugging in a >15A device into this outlet for use on a nano tank!

So I can't run my home AC compressor off the outlet? tongue.gif

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The entire unit is fused for 15 amps. I have not had good luck with their fuses though. I had a unit fail in one socket that shorted. It tripped the house breaker before the fuse went. When you flipped on the house breaker the dc8 emitted a flash of light but the fuse never tripped. I opened it up and it had a shorted component. I need to attempt the repair.

 

In general you want your electrical components to be rated at higher amp specs than the protective components of your circuit. In this case, the protective components are the fuse on the DC8 and the breaker. Using a triac that can handle more current than it will ever get is safer/less of a fire hazard than the opposite. Having a 12 amp triac in a power strip rated at and fused at 15 amps is a fire hazard in my opinion. It can get too hot without tripping the breaker or the fuse.

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  • 2 weeks later...

Good news: Disassembly/reassembly didn't affect the other outlets

Bad news: New triacs didn't make a difference.

So some tips if you try this:

1. Make sure your triacs are shorted. The ones on my malfunctioning outlets were testing fine but I figured since I had the thing open I would replace them anyway - you never know.

2. You do not need to desolder the outlet plugs, just pry the plugs from the outside -they are in two pieces. Just get a small prying tool under them to release the tabs you can see from below.

3. Likewise, when putting it back together, put the plugs back on before you close the unit - it takes a decent amount of force to seat them.

4. As a novice, this took a lot of time - unless you are a pro it is probably not worth the effort - used DC units go between $70-80.

5. That being said, if you want to try it I have a few extra triacs.

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  • 8 months later...

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