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Old 5th February 2010, 10:22 AM   #441
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Quote:
Originally Posted by juluska View Post
żare the secondary wires of the toroidal correct? What is the exact model of this toroidal? Are the secondaries red-yellow-blue-green?
I guess so, cos i have the correct voltage: +/- 40 V
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Old 5th February 2010, 01:11 PM   #442
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Originally Posted by Ruwe View Post
The point is that on these boards the input and output grounds are disconnected.
When you say "connected to the power components ground", I understand that you're talking about the output (speaker) ground.
No, i mean the ground from the Power supply...
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Old 5th February 2010, 01:12 PM   #443
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Originally Posted by Ruwe View Post
Is the same problem on both channels?
Yes

Quote:
Originally Posted by Ruwe View Post
Are you sure the resistors in the base of the differential pair are correct values? You should have 27k in the feedback path and something that gives you a sum of 27k on the input. I've seen combinations of (24k+2.7k) or (22k+4.7k).
Yes they have the right values

Please have a look on the attached schematic, i measured almost all Transistor voltages.
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File Type: jpg Scan-100205-0001.jpg (896.5 KB, 729 views)
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Old 5th February 2010, 06:27 PM   #444
Ruwe is offline Ruwe  Europe
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Originally Posted by sangeet2 View Post
Yes

Yes they have the right values

Please have a look on the attached schematic, i measured almost all Transistor voltages.
Very bad. Now try first the obvious in the following order:

1. With no power applied, check that the ground at the input is connected to the ground at C6. You have to measure 0 ohms between these points. If not, connect them with a wire.

2. Q4 is dead if I believe your measurement, but I don't. You can't have 39.8V supply and 11.2V at the emitter of Q4, because it will fry immediately the 330 ohms resistor. You have to measure everything with reference to ground or it doesn't help at all.

3. Check your power supplies after the 1N4007 diodes. Do you have 39V/-39V ?

3. BC550 in the current source may be gone too. Are you sure you measure -8.5V on both collector and emitter? ... If yes, it's gone.
More likely though the collector is to -1.8V. Please, re-check.
And again, if the emitter is at -8.5V, the other 330 ohms in the negative rail must be fried. Also 2x1N4148 should give you about -38.5V at the base of this transistor. It doesn't make any sense!
The Q1 must be with all voltages around negative! At least the 39.4V must be -39.4V

4. The differential pair voltages don't make sense.
-1.8V and -8.5V in practically the same point (the emitters)? If yes, both don't look like transistors anymore.

5. Not very important right now, but: change 27k on the input with 24k for better balance.
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Old 5th February 2010, 07:55 PM   #445
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Originally Posted by Ruwe View Post
Very bad. Now try first the obvious in the following order:

I found out, that they delivered C560B instead BC550
I have a bunch of BC549 in my box, I think i should exchange them all and measure again. Will not do that before tomorrow...


1. With no power applied, check that the ground at the input is connected to the ground at C6. You have to measure 0 ohms between these points. If not, connect them with a wire.


I measure zero Ohm


2. Q4 is dead if I believe your measurement, but I don't. You can't have 39.8V supply and 11.2V at the emitter of Q4, because it will fry immediately the 330 ohms resistor. You have to measure everything with reference to ground or it doesn't help at all.


The 330 Ohms are both ok, all measuring are refering to ground, of course



3. Check your power supplies after the 1N4007 diodes. Do you have 39V/-39V ?


Yes


3. BC550 in the current source may be gone too. Are you sure you measure -8.5V on both collector and emitter? ... If yes, it's gone.


Looks like its gone then


More likely though the collector is to -1.8V. Please, re-check.
And again, if the emitter is at -8.5V, the other 330 ohms in the negative rail must be fried. Also 2x1N4148 should give you about -38.5V at the base of this transistor. It doesn't make any sense!
The Q1 must be with all voltages around negative! At least the 39.4V must be -39.4V


It is negative, I made mistake by drawing...sorry, but the other voltages are positive...


4. The differential pair voltages don't make sense.
-1.8V and -8.5V in practically the same point (the emitters)? If yes, both don't look like transistors anymore.


This is what i measured.


5. Not very important right now, but: change 27k on the input with 24k for better balance.

I will keep this in mind, thanks alot for your help
Not sure at the moment if I need to xchange other parts after xchanging all C560B
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Old 6th February 2010, 12:08 AM   #446
Ruwe is offline Ruwe  Europe
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Originally Posted by sangeet2 View Post

Not sure at the moment if I need to xchange other parts after xchanging all C560B
The drivers Q1, Q2 are the only that look OK. May be Q5 either. The rest is suspicious.

After you exchange practically all small transistors, measure again the voltages at the same points and attach the schematic again.

BC560 is completely different from BC550!!!

BC560 is PNP, and BC550 is NPN. So, yes, all is wrong if you use 560 instead of 550.
BC549 is NPN and will work, but there is a big chance to burn them again, because they are only 30V transistors. You better find BC550, BC547 or BC546, letter "B" or "C". "A"s gain is too low.

Good luck!
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Old 6th February 2010, 01:35 AM   #447
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Ruwe, you're a Good Man! Sangeet, well, you're trying. And my boards haven't arrived. So I keep watching.... Sangeet hurry up so when my boards arrive I can have Ruwe for some troubleshooting...... any chance???
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The stuff you don't know always humbles us.........
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Old 6th February 2010, 04:04 AM   #448
Ruwe is offline Ruwe  Europe
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Originally Posted by crispycircuit View Post
Ruwe, you're a Good Man! Sangeet, well, you're trying. And my boards haven't arrived. So I keep watching.... Sangeet hurry up so when my boards arrive I can have Ruwe for some troubleshooting...... any chance???
No transistor can sustain high reverse voltages. PNP replacing NPN types is very poor handling from China ...

I'll be here ... but if you are careful while placing and soldering the components, no troubleshooting is needed. This amp is very simple and trouble free. That's why it's impressive that it actually sounds so good...
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Old 6th February 2010, 04:14 AM   #449
limono is offline limono  United States
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Is it really worth the truble to buy and build one? Will it compare to Nait 5 ?
This thread is way to long
Regards, L
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Old 6th February 2010, 05:44 AM   #450
Ruwe is offline Ruwe  Europe
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Originally Posted by limono View Post
Is it really worth the truble to buy and build one? Will it compare to Nait 5 ?
This thread is way to long
Regards, L
Well, I don't know... Depends on how you build it, some small but important details in adjusting it, and in quality of some components, proper grounding scheme etc ...
Mine measures very well and sounds like a real Naim. I've heard Naim systems and mine sounds like one of them. I've never compared it side by side though. If you ask me would I buy NAP-150 for example, I'll say "no", because for the money difference I don't expect anything more... unless I can buy it for less than 500$... It would look nice next to the CD5i
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