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Class D Switching Power Amplifiers and Power D/A conversion

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Old 19th December 2008, 08:44 AM   #221
col is offline col  Australia
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I can order a NTE1 myself and tweak a good working network and post my findings if you like Col?
V-bro That would be awesome! There are a couple of us using the NTE-1 to balance up connections with the Tripath/41hz amps over here now. It's a must connecting to pro-audio gear.

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Old 19th December 2008, 12:54 PM   #222
v-bro is offline v-bro  Netherlands
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Ordered them, they should be here monday, will post my findings here if nobody minds.
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Old 19th December 2008, 01:20 PM   #223
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Originally posted by v-bro
Ordered them, they should be here monday, will post my findings here if nobody minds.
Please do as I need it too and don't have a strobe.
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Old 19th December 2008, 05:13 PM   #224
v-bro is offline v-bro  Netherlands
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I hope they arrive monday, otherwise they'll certainly be there tuesday.

I do have a circuit design for OEP A262A7E (1:1+1:1) for a dual primary and paralelled secondary setup. This would need a 47nF cap and a 1,8K resistor.

And for the NTE-4 it would have to be like I posted earlier...

I must say that the OEP tranny surprised me by the price/quality ratio they offer. If you were to order these then order the MU-metal shielding casing along with it, it's an accessory.

The scope images above were from the OEP, but not with the most ideal resistor value (1,6K) yet, later on I placed them on a piece of experimental board and added the correction network in SMD components...In SMD I did have 1,8K in stock, this made the square wave even better!
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Old 22nd December 2008, 10:50 AM   #225
tsnell is offline tsnell  Australia
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Hi Everybody,

I finally got around to testing my amp 9 basic and I cannot get it working. The setup is:
• I am using an ipod as input with a 3.5mm to rca cable.
• The outer barrel of each rca socket is connected to the outside pins of j1 and the centre of the rca to the inside pins.
• J1.1 and j1.2 are paralleled and j1.3 and j1.4 are paralleled for stereo use.
• The cap near the supply input is connected to the diode as noted in the forums.
• Jumper j2.1 and j2.3 are closed. No other J2 jumpers are closed.
• I am using a lab power supply set to around 13v.
• Each of the speaker outputs is connected to an P Audio HP10 4 ohm speaker.

When I power on there is a very slight click from the speakers. Then nothing. The chip heats up very quickly, I am holding my finger on the back of the chip and power down once it gets hot to touch.

Is there a debugging or troubleshooting guide somewhere? What voltages should I be reading where? I have access to an old oscilloscope and a DMM.

Thanks in advance for any help you can give me.
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Old 22nd December 2008, 11:40 AM   #226
v-bro is offline v-bro  Netherlands
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Hi,

Bad news!

What resistance do your speaker outputs measure? I mean at power off and separate, not paralleled...

Are you sure you paralleled the right points?

Are there any status leds on or off?

What DC do you measure at the outputs? (perhaps clip on a small heatsink to test this)

Follow the inputs with a DMM towards the blue caps and from the blue caps towards the inputs on the chip. Do this too with the speaker outputs. Measure for continuity and shorts Between them...

Can you shoot some pics?

PS, trannies have not arrived yet...
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Old 22nd December 2008, 08:07 PM   #227
tsnell is offline tsnell  Australia
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Hi V-Bro,

Should I be starting a new thread for this? Anyway for now I will leave it here. So the outputs are not bridged/paralleled at all, only the inputs. Each of the 4 outputs goes directly into one of the HP10 drivers. I’ve attached some photos.


Click the image to open in full size.

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For the test setup I had switches connected to awake and mute and was using the little back bridge connector on AM mode. I know my soldering skills are not the best but I am almost certain I haven’t crossed anything. Can you see anything obvious?

Is there a “boot order”, ie bridge AM, power on, awake on, wait 5 sec, mute off, music on. Or something similar?

I will attach a heatsink as soon as I get home and do some more testing.
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Old 22nd December 2008, 08:42 PM   #228
v-bro is offline v-bro  Netherlands
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Yes, I think it's better to continue this in a thread at 41hz forum.

I do see a few things that are perhaps thye cause of your amp not working, for instance some blobs of solder where the resistors are near the sleep and on/off jumpers.

On top of that you're not running in class D, you should close the third jumper there (look at the bottom of the PCB and read the assembly instructions once more) , though:

DON'T jumper this one with the amp on!!!!!!!!!!!!!!!!!!!!!!!!!!

Then there are solders on the output filter caps (the glossy red ones near the speaker outputs) that should not be done so rich, hold the board against a strong lamp and you'll see the copper around these pads should NOT make contact to these pads! Try and clean your solders up a bit better, then polish up the board with pure (99%!!) alcohol and some paper or even better with some printed circuits cleaner.

I'm pretty sure this amp is still alive, with a faint heartbeat though....
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Old 22nd December 2008, 08:46 PM   #229
v-bro is offline v-bro  Netherlands
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PS. the mod with the cap to diode wire isn't necessary any more with the latest board revisions.... have another look with a strong lamp...

The strong lamp method is sadly a far too much overlooked very helpful tool to troubleshoot and make a good diagnosis of a PCB and the soldering, plus it gives yourself a good 'insight' of the circuitry ...
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Old 22nd December 2008, 08:51 PM   #230
tsnell is offline tsnell  Australia
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Hi V-Bro,

I did have the 3rd set of pins jumpered I had taken it off but it is the black jumper shown on the right of the last photo.

I will clean up the solder joins and see if that helps.

Going to post on the 41Hz forum now.
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