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Old 4th August 2014, 07:57 PM   #21
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OK, so putting new CCSs back and I'm back to square one again; sound is extremely faint. Voltages at the CCS are: +478V at A, -0.98V at G and K. Essentially zero volts across both R13/23. I definitely haven't mishandled 4 separate devices (I used a grounded antistatic mat, wrist strap etc.) yet when I used the resistor in place of the CCS the rest of the amplifier works fine. There must be something systematically making the chips not work, but I'm stumped as to what it is. I've taken some more photos: http://www.adrianbaugh.org.uk/amp10.jpg, http://www.adrianbaugh.org.uk/amp11.jpg and http://www.adrianbaugh.org.uk/amp12.jpg in case they're of use.

Is it worth trying IXCP10M90S parts in case the 10M45Ss are being fried by the startup surge? (But I'd have thought someone else would have encountered the issue before if it was a problem, I'm using the recommended power trafo after all.)
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Old 4th August 2014, 08:01 PM   #22
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(I know the solder joints don't look great, I was ensuring not to overheat the devices, but there is good continuity between the 10M45S legs and the pads of the resistors along from them...)

Oh, and is it just me or is the bolt hole in slightly the wrong place on the board, I've bent the CCS legs right before the thick bit (so as not to stress the bit where they go into the device body) but it's like the bolt doesn't quite line up with the hole.

Last edited by adrianbaugh; 4th August 2014 at 08:13 PM. Reason: further question
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Old 5th August 2014, 05:33 PM   #23
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Are you sure you connected the IXYS part correctly?
It looks like it's upside-down?!?
That would explain why it does not line up with the hole, right?
To me, the PCB looks like it is intended to have the CCS IC on top of the heatsink. But then the IC would have to be flipped around (metal fin toward bottom). Please check again the right polarity of the CCS IC as I am not familiar with the SSE board.

Cheers,
Martin
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Old 5th August 2014, 07:10 PM   #24
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No need for a 10M90 - the 450V rating is Vak, meaning the difference between the two. At start-up the drive tube isn't conducting, so Vak is very small.

@bayermar, the orientation looks correct according to tubelab.com site for inverted installation. Granted, I've never built an SSE.

Where were these purchased from?
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Old 5th August 2014, 07:17 PM   #25
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Quote:
Originally Posted by jpjones3318 View Post
No need for a 10M90 - the 450V rating is Vak, meaning the difference between the two. At start-up the drive tube isn't conducting, so Vak is very small.

@bayermar, the orientation looks correct according to tubelab.com site for inverted installation. Granted, I've never built an SSE.

Where were these purchased from?
Yep i'm doing the inverted build. I bought the parts from Littlediode on eBay. (Yes, I know, but I've used the seller for chips before and they've been reliable in the past. It seems very difficult to source the ixys parts from the mainstream parts sellers in the UK (Farnell, RS etc.) I didn't want to have to use Mouser and pay the high shipping charge, but at this rate it would have worked out cheaper.)

When the CCSs are not soldered in, is there a simple test I can do to see if they're OK - resistance between legs or something?
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Old 5th August 2014, 08:02 PM   #26
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Do you have a bench supply or something that can serve the purpose - ~20VDC?
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Old 5th August 2014, 09:20 PM   #27
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I could lay my hands on one, yes. Would a little higher or lower matter?
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Old 5th August 2014, 10:19 PM   #28
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Shouldn't.

If you look at page two of the data sheet here http://ixdev.ixys.com/DataSheet/98704.pdf you'll see a simple schematic. If you set this up, with Vd being your ~20VDC supply, you can measure across Rk and find the current going through the resistor. If the voltage drop is 0, the CCS isn't working.

Use ohms law to find the current through the resistor, which should correspond to the chart below the schematic - 330R should be ~9mA.
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Old 6th August 2014, 02:12 PM   #29
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Your parts are installed correctly. The screw holes line up on my Ixys parts.

There have been issues in the past with counterfeit 10M45's in SSE's and TSE's. The fact that the leads don't bent the same way as mine makes me suspicious. Can you post a picture of the top of one of your parts? Is there any resistance reading between any of the leads on the parts that you have removed? Some counterfeit parts have nothing at all inside them, others are just some random device that the counterfeiter had bunches of....those usually short out when fed 400+ volts leading to too much current, you have no current.
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Old 6th August 2014, 07:56 PM   #30
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Hi,
Here is a photo of the chips I've tried, plus 2 new 900V parts I bought on the off chance they might work better: http://www.adrianbaugh.org.uk/chips.jpg

I'm becoming suspicious too now because the printing appears different between the various chips and is wearing off some. At first I thought it might just be different batches, but combined with none of them working... All the chips show >20Mohm (the max scale on my multimeter) between any two legs.

Looks like I'm off to Mouser. But I think until they turn up I'll tack in those 2W resistors and enjoy the amp for a bit, even if it won't sound quite as good till I get hold of the genuine parts.

Thanks for all your help, I'll post an update in due course.
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