Amp protects with or without load.

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Deadly Sones

Deadly Sones

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Joined 2011
I rebuilt the output section on this American Bass 1100.1. Everything seemed good. Nice waves everywhere. Put it back into the case and gave it a 1 ohm load. Plays for about 20-30 seconds protects.

Restart it, plays... protects... remove the load, turn it on... green light for 20-30 seconds... protects.

I'm thinking possibly an output filter inductor? Could anything else be the problem?
 
Note: With no RCA connected, load or no load it does not protect. It only has -0.048DCV offset on output terminals. It's only pulling 6.5 amps idle. Sooo... preamp possibly? Or still might be filter inductor?
 
Remove RCA, restart... green light. No protect.

So just black lead on main ground and red lead on RCA ground? I read 0.008vdc.

Yes, I use a car audio deck as my source. They are all grounded together.

I should also mention I repaired another 1100.1 today with the exact same lot of parts and it's running fine. Using the same bench to test.
 
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Does pushing/pulling/twisting the inductors seem to make a difference?

Does touching the RCA center conductor on the amp (no RCAs plugged in) cause it to go into protect? It's normal to have a hum when you touch the center conductor with your finger. I was wondering if that sort of signal would send it into protect.
 
I touched the center rca conductor on the amp from inside where they come out the back of the connector. Nothing happened. It did not protect. I twisted, pulled, wiggled every output filter inductor. It still did not protect.
 
When I first connect the remote power I do hear an arc sound coming from somewhere in the output section split seconds after the remote wire is connected and just before the relays release muting. Might just be something else switching on... but it sound suspicious
 
Did it produce a hum through the speaker when touching the RCA input?

Without a signal, is the amp producing rail to rail oscillation on the output transistors (or input to inductor)? Some won't oscillate until it sees a signal.
 
Since I touched the RCA conductor and made that humm noise, and/or twisted inductors, the idle current dropped about 1 amp. now idling at 5.3 from 6.3-4 amps.

Edit: Nvm... reset it and back to 6ish amps... which is normal for these amps.
 
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So, connect RCA back and test with it off, from RCA shield to head units case? RCA shields have 0 ohms... both connected to the amp and not connected to the amp.
 
Ok... so in trying to see if part of the preamp section was the problem... I switched the amp to slave, no speaker load, added rca to the slave input... played sound basically through the indicators... and protected... so seeing as the slave input pretty much bypasses most of the input stuff... does it mean likely inductor? Even though twisting, pulling pushing, etc seems to make no difference.

Without the RCA input the amp never protects. Left it running for over 2 hours. Only protected after a RCA is attached to it. 🙁
 
I wouldn't be running a class d amp without a speaker/load connected.
If you do the output inductor will ring like mad and possibly blow the output capacitor.
On my designs I always make the output capacitor a much higher voltage than normal just in case.

On irs2029 based class d amps having no load sometimes stops it oscillating and the output sits at +17VDC.
 
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