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Old 10th March 2012, 11:32 AM   #21
Lucas_G is offline Lucas_G  Netherlands
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On the two ZTX 450 I measured between C and E a voltage of 4,5 Volt

On the three IRF 9610 I measured between G and D a voltage of 3,65 Volt

On R11 I measured 5,2 Volt and on Z5 I measured 8,9 Volt


I think this all seems ok...
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Old 10th March 2012, 12:00 PM   #22
generg is offline generg  Germany
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Hm, hm there are more voltages on the circuit please check them all.....
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Old 10th March 2012, 12:02 PM   #23
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Can you measure the test voltages as per the diagram.

Across R11 you should have between 4 & 5 V this will establish that the CCS is working.

Q1 / Q2 Source to 0V (Power Gnd) should be 4V.

Across R14 should be bewteen 4 & 5V.

If these are OK the active components at the input would seem OK.

If they are OK just replace all the 220uF caps. They are prone to failure in the hot environment of the Aleph.

If that doesnt cure the problem, check all other caps and the feedback loop.
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Old 10th March 2012, 12:06 PM   #24
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Across Q1 there should be approximately 36V D-S

Across Q2 there should be about 40V D-S
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Old 10th March 2012, 12:11 PM   #25
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Your output Offset of 12mV would tend to indicate that the DC quiescent condition is stable but everything goes haywire when an AC input is applied.

This, to me, would indicate a capacitor failure or even a joint that has gone bad.
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Old 10th March 2012, 12:21 PM   #26
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Originally Posted by KatieandDad View Post
Can you measure the test voltages as per the diagram.

Across R11 you should have between 4 & 5 V this will establish that the CCS is working.

Q1 / Q2 Source to 0V (Power Gnd) should be 4V.

Across R14 should be bewteen 4 & 5V.

If these are OK the active components at the input would seem OK.

If they are OK just replace all the 220uF caps. They are prone to failure in the hot environment of the Aleph.

If that doesnt cure the problem, check all other caps and the feedback loop.
Across R11 I get 5 V.

Q1 / Q2 Source to power ground is 3,65 V

Across R14 I get 4,65 V
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Old 10th March 2012, 12:24 PM   #27
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Originally Posted by KatieandDad View Post
Across Q1 there should be approximately 36V D-S

Across Q2 there should be about 40V D-S
Across Q1 I get 48,6 V

Across Q2 I get 53 V
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Old 10th March 2012, 12:25 PM   #28
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If you read that brief appearance of my diagnosis that I have just deleted - it was wrong.

Next bit is to just replace the three 220uFs C5, C9 and C10.

They're pennies and very difficult to test.

Just use cheapies to prove a point. Once its working you can replace them with exotic parts.

I'll bow to someone with a bit more experience with these amps, I've only got a second hand Aleph 4 that was built by a member of my family.

Try using some rather large 10R resistors in place of the fuses during fault condition testing.

Last edited by KatieandDad; 10th March 2012 at 12:32 PM.
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Old 10th March 2012, 12:29 PM   #29
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Originally Posted by KatieandDad View Post
Your output Offset of 12mV would tend to indicate that the DC quiescent condition is stable but everything goes haywire when an AC input is applied.

This, to me, would indicate a capacitor failure or even a joint that has gone bad.
For the 220 uF caps I used Panasonic FC

For the small C8 (10pF) I used this one (styroflex?):
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File Type: jpg CapOnC8.jpg (14.1 KB, 73 views)
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Old 10th March 2012, 12:34 PM   #30
Lucas_G is offline Lucas_G  Netherlands
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Quote:
Originally Posted by Lucas_G View Post
Across Q1 I get 48,6 V

Across Q2 I get 53 V
Is this within limits?

I als checked Q3 and I get there 41,3 V between D and S...
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