diyAB Amp The "Honey Badger" build thread

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Kay Pirinha

Kay Pirinha

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Joined 2011
RickRay said:
Be sure and clip the 10R when you are finished. I left them in place and installed the fuses. The fuses will bypass the resistors until they blow, if something happens. Something did happen with mine, self-inflicted, and since it had the resistors installed, blew the fuse, then took out one of the outputs. If I had removed the resistors, pretty sure the fuse would have saved the ouput. It has MT-200 Sankens, pretty robust.
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No. If you'd followed the advice to install low-wattage 10 Ω resistors, these immediately would go up in smoke and open if anything were wrong and draw excessive current, hence protect the devices also.

Best regards!
 
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RickRay

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Joined 2014
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I would think a resisitor, of any wattage, would have a much longer "blowing" time than a fuse. But hey, I'm not an expert. I'll stick with only fast blow fuses on my rails. Of course, even a fast blow fuse may not protect the outputs depending on the circuit, the device and the circumstance creating the short.
 
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Chiptech

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Joined 2005
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RickRay said:
I would think a resisitor, of any wattage, would have a much longer "blowing" time than a fuse. But hey, I'm not an expert. I'll stick with only fast blow fuses on my rails. Of course, even a fast blow fuse may not protect the outputs depending on the circuit, the device and the circumstance creating the short.
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Well, I went ahead and tried the 10R resistors. Got the same result: very little power across TP 1 & 2. Pulsating on/off bulb. I wonder if it's my trusty soft start. Is that getting in the way somehow? Or I have a short, but where? Any likely places to start probing? I feel confident that the pots are set correctly to begin biasing. The board looks clean, nothing burned that I could see.
 
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jwilhelm

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Joined 2014
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That 250 to 450mA flowing with the bulb and 10 ohm resistors limiting the current. You have some problems on the amp board. Your soft-start is doing it's job but you have something drawing too much current so it resets and starts again.

Start by verifying you have the correct components everywhere. It's really easy to mix up transistor locations. Take some resistance readings between the power rails to ground. Also from the power rails to the output rail. They should all be very high resistance. Check for obvious mistakes like connecting power backwards, this is an easy mistake to do too.
 
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Chiptech

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You had me at "Check for obvious mistakes like connecting power backwards, this is an easy mistake to do too."

Amazing what can be accomplished when reading words correctly. :mad:

The current readings with 10R resistors in are:

R7: 0.171 DCV
R30: 0.000 mV
R17: 0.006 mV

I had checked all the power rails to output rails and got high resistance.

Hopefully I will get time tomorrow to start biasing.

Xmas came early for me.

Thanks for your help.
 
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