Orion HCCA 225 digital reference blows fuse

[Perry Babin]

Remove the two transistors that were directly connected to the two resistors that caused the most significant drop in the voltage across the other resistors when you removed the resistors from the circuit.

If you haven't yet remove the clamp from the transistors, do so as is shown in the following graphic.
http://www.bcae1.com/temp/orionampclamps.swf

 

[ash4kel]

I removed the transistor that I suspected to be the bad one and tested. Results are 0.000v on all resistors. I tested with the resistors all tied back to the board. So am I to assume that this is the culprit, or is there more to test?

 

[Perry Babin]

If it powers up and all resistors read 0.000, clamp everything down and see if it produces audio.

 

[ash4kel]

I know this is a stupid question, but I assume at this point I reinstall the fuse now and try the audio, correct?

 

[Perry Babin]

You can replace the 2 ohm resistor with a fuse (nothing larger than 15 amp for now). If it produces audio, you'll need to replace all of the output transistors in that channel. If it doesn't produce clean audio from both channels, you'll have to do a bit more troubleshooting.

 

[ash4kel]

I have no audio at all. Now this is a digital reference with a pop top. I have no idea how the crossover needs to be set or if this could have any impact. I did remember to take the rca's off the working amp, but no sound at all.

 

[Perry Babin]

What modules do you have in it?

 

[ash4kel]

Here is the crossover and bypass.

 

[Perry Babin]

Set the switches to on for the bypass module.

 

[ash4kel]

Ok, I have it hooked up to my full range speakers but all I am getting is lows coming out of amp. This makes since, since I believe I had it set for a sub. But I just looked for my book and cannot find it. I was going to try and set it for full range. But there is sound out of both sides, I just don't know if its clear until I can set the crossover to full range.

 

[Perry Babin]

Remove the crossover module. Set the jumpers on the header and for the location where the crossover was located as shown in the attached photo.

 

[ash4kel]

I found my book and set crossover to high pass. I have good sound out of both sides.

 

[ash4kel]

So it sounds as if what I should do is replace the transistors on that side. If that is the case I want to thank you. You are a God send to us out here who want to save these amps. There is so little info out there, your knowledge is priceless. Thank you for taking your time to deal with amateurs like myself, I have learned a lot.

Scott

 

[ash4kel]

One last thing, do you have the full exact part numbers for the 2n6488 and 2n6491 transistors. When I looked them up on digi key, they have some suffix letters and or numbers. I want to make sure I get the correct parts. Thanks, again.

 

[Perry Babin]

The suffixes aren't generally significant for output transistors like the 6488 and 6491.