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Old 21st February 2009, 11:02 AM   #251
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Hi Richard,

I still don't know where you are taking your readings from so, can you please give me the DC readings from the points in the picture.
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Old 21st February 2009, 11:15 AM   #252
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Quote:
Originally posted by audio1st
Hi Richard,

I still don't know where you are taking your readings from so, can you please give me the DC readings from the points in the picture.

Iím in the office at the moment but I will provide these readings later this afternoon

Iíve been taking the ground connection from the output end of the board.

Everyone going to breathe a sigh of relief when this is sorted!
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Old 21st February 2009, 11:36 AM   #253
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Hi Richard,
If you connect the neg probe to Gnd and use the pos probe to take readings, they should all be -V readings.
When you say across R2 and across zener, 34V and 28V, these items are in series across the supply and would mean you had a supply V of at least 62V?

If you measured R2 to Gnd and got -35V, this means that if your supply is about -36V then only 1V across R2...
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Old 21st February 2009, 12:16 PM   #254
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Quote:
Originally posted by audio1st
Hi Richard,
If you connect the neg probe to Gnd and use the pos probe to take readings, they should all be -V readings.
When you say across R2 and across zener, 34V and 28V, these items are in series across the supply and would mean you had a supply V of at least 62V?

If you measured R2 to Gnd and got -35V, this means that if your supply is about -36V then only 1V across R2...
All voltages are -V

OopsÖI didnít realise it would only be 1v across R2.
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Old 21st February 2009, 12:57 PM   #255
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I think we are nearly there

Just need to change the V+ rail zener and make sure the 1k connects to "Gate" and the 130r to the "Source" of the V+ rail J309.
Then see how similar the output V- and V+ voltages are?
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Old 21st February 2009, 01:02 PM   #256
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Originally posted by audio1st
I think we are nearly there

Just need to change the V+ rail zener and make sure the 1k connects to "Gate" and the 130r to the "Source" of the V+ rail J309.
Then see how similar the output V- and V+ voltages are?

I think I might buy an electronics book!
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Old 21st February 2009, 06:43 PM   #257
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Here's the latest...

Click the image to open in full size.

-V

'A' -28.3v
'B' -33.2v
'C' -34.2v
Output -26.1v

+V

'A' +27.6v
'B' +28.6v
'C' +28.7v
Output +25.5v
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Old 21st February 2009, 07:52 PM   #258
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Hi Richard,

-V readings look OK, you may want to try a different zener (closer to 27v) 28.3 is 5% error.

+V has a problem with your input voltage (28.7v) is low, is the problem on the rectifier board or is it the bleeder resistor?
Scrub that, you may have measured the wrong point? If you measure across the +V input and get near 35v everything is fine!
PS, did you swap the 130r and the 1k on the V+side?
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Old 21st February 2009, 08:56 PM   #259
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Just a warning Richard,
If you haven't isolated the heatsinks from the 911 and 912, the heatsinks will be at their collector voltage. This means when you join the grounds together you will have 70v between heatsinks.. Make sure they don't touch each other..
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Old 21st February 2009, 09:13 PM   #260
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Quote:
Originally posted by audio1st
Just a warning Richard,
If you haven't isolated the heatsinks from the 911 and 912, the heatsinks will be at their collector voltage. This means when you join the grounds together you will have 70v between heatsinks.. Make sure they don't touch each other..

The heatsinks are isolated from one another and are not touching any other components or jumpers. I've also put thermal compound between the sink and transistor
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