How to build a 21st century protection board

[RickRay]

I was using power supply ground instead of digital ground. It is starting to make more sense now. I have 12V at the emitter, collector, both sides of R9 and 10V at pin 4 of U2. I need to be looking at Q6.

 

[jwilhelm]

All the isolation on the grounds makes these good in operation but it gets tricky testing! Yes it looks like your issue is in the area of Q6. It's base gets a 5V signal from the control board to turn on through R11 which in turn should ground the input of U2.

If you find pin 4 of U2 is actually being grounded but the output fets aren't turning on look for a short between the gate and the source on Q8 and Q9 shorting the output of U2. This happens quite often and is hard to see.

 

[RickRay]

Very hard to see, but the base of Q6 isn't attached to it's pad. Resoldered and everything is working perfectly.

1 more question, can I power both DC boards from the rails of one channel, or should I power each board separetely from each channel board?

You have literally spent most of today answering my crazy questions. I can't thank you enough!!! if you need someone to write testimonies or reviews let me know, it's the least I could do.

 

[jwilhelm]

Good to hear you have it working! The detection circuits should connect directly to the power supply for the amp channel it's monitoring. If you connect to the amplifier itself you may see some false triggering due to voltage fluctuations.

 

[RickRay]

I'm using one of your Dual Board power supplies for two channels, I'll connect to that somewhere.

Again, I can't thank you enough, I've learned a lot doing this!

 

[savvas]

Is the protection board shutting the amp down when this happens?

Yes. It doesn't happen always. My guess is that it detects DC before the SSR so it doesn't do any harm to the speakers 'cause the SSR (on the OPS module) are closed.

 

[jwilhelm]

Those versions seem to be sensitive to static charges. It seems to be more from the supply rails to the DC detection circuit. In normal operation it works well, it just doesn't like to be tampered with in operation.

 

[savvas]

Thanks jwilhelm for the info. I'll check the DC offset at the speakers, if it's OK I would only have this odd indication for few seconds.

 

[RickRay]

Verification of Current sensing wires





I connected the current sensing wires to TP1 and TP2 shown on the circuit board picture.
TP1 connects to the emitter of Q19 and TP2 connects to the emitter of Q17.
Is this placement correct?

 

[jwilhelm]

That sounds correct.

 

[RickRay]

Thanks! I'll post some pictures after this weekend, waiting on a couple nuts and a switch to finish the project.

 

[RickRay]

Finally got the right nuts to be able to mount the DC Protection Boards.

 

[jwilhelm]

You mean nuts to fit the binding posts? If so where did you find them? I've given up and started machining my own.

 

[RickRay]

Place called Little Machine Shop in California.

M8X0.75 thread nuts and washers

Search For... - LittleMachineShop.com

 

[jwilhelm]

Thanks! That looks like a handy site for tooling too.

 

[vzaichenko]

RickRay - beautiful job! Solid build

 

[RickRay]

Thanks Valery!