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Old 28th April 2013, 07:34 PM   #2121
FdW is offline FdW  Netherlands
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The Tremeloes - Silence Is Golden (HQ) - YouTube
3 days nothing?
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Old 28th April 2013, 09:56 PM   #2122
pdul is offline pdul  Denmark
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maybe there is something else to do but sit at the puter
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Old 29th April 2013, 08:28 AM   #2123
hesener is offline hesener  Germany
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Working on another couple Paradise boards, one is working fine but the other is stuck at 15V at the output.....
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Old 29th April 2013, 08:49 AM   #2124
RCruz is offline RCruz  Switzerland
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Originally Posted by hesener View Post
Working on another couple Paradise boards, one is working fine but the other is stuck at 15V at the output.....
Most interested in your findings... Had a similar issue that took me a while to correct... mybe you find a better way
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Old 30th April 2013, 07:23 AM   #2125
hesener is offline hesener  Germany
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Working on another couple Paradise boards, one is working fine but the other is stuck at 15V at the output.....
Boards are working fine now, and the error was quite interesting.

A lesser-known fact is that bipolar transistors work both ways (collector and emitter reversed). the current gain is low, but if the circuit does not depend so much on this, at first glance it looks fine.

In this case, Q15 and Q16 were inserted the wrong way. They are the "bottom" transistors of the current mirror used in the current source for the input stage, and since this is a stacked current source , and the transistors were still doing something, it was not immediately obvious. Instead, there was some offset, which I thought was caused by mismatch in the transistors. But it was a mismatch between the upper and lower current mirror, caused by the reverse mounting. The servo could not correct this amount of mismatch - an indication how weak it actually is. Once the transistors were mounted correctly, everything worked fine.

Many thanks Ricardo for the numbered drawing, I used it extensively in this case!
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Old 30th April 2013, 09:11 AM   #2126
RCruz is offline RCruz  Switzerland
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Glad to know that I could help.... You are very welcome
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Old 30th April 2013, 09:14 AM   #2127
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Frans,

I'm doing a bit of catching up on this thread. Regarding your post "#1772 NJF selection for the PSU" - what about J109?

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Old 30th April 2013, 10:07 AM   #2128
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Frans,

I'm doing a bit of catching up on this thread. Regarding your post "#1772 NJF selection for the PSU" - what about J109?

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Sven
Not possible, the J109 needs an Rgs of more then 5K for 1mA, thus dropping more than 5Volts (no more than 2Volts (or less) is best).
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Old 30th April 2013, 10:22 AM   #2129
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I'm sorry - I'm one of these "color by numbers" guys. I don't really understand what happens and I need simple instructions .

You write the J310 is not ideal. I assume Rgs is R108 (3k3R) in my board? So what I have today is a J109 (came with the GB) and 3k3R. Please be certain you do not mistake the J109 for something else, we caused some confusion earlier in this thread because of this . Anyways, I take it from your answer that this is "not possible".

So you suggest SK170. I will have to replace the 3K3R with something around 360R? Does it matter if SK170 BL or GR?

Thanks for you patience.
Sven
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Old 30th April 2013, 10:36 AM   #2130
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by Abraxas336 View Post
I'm sorry - I'm one of these "color by numbers" guys. I don't really understand what happens and I need simple instructions .

You write the J310 is not ideal. I assume Rgs is R108 (3k3R) in my board? So what I have today is a J109 (came with the GB) and 3k3R. Please be certain you do not mistake the J109 for something else, we caused some confusion earlier in this thread because of this . Anyways, I take it from your answer that this is "not possible".

So you suggest SK170. I will have to replace the 3K3R with something around 360R? Does it matter if SK170 BL or GR?

Thanks for you patience.
Sven
IMO the best choice is the J113 (using a 1K Rgs resistor). But all resistors needing a 2K or less Rgs are good. The J109 is currently the worst one simulated
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