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jts1957 |
Posted: Sun Nov 09, 2014 3:01 am Post subject: |
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So that leaves: hoping to find a through hole part in series with the foil trace you need to isolate; looking for a easier part/point further forward or behind the part/point first intended; purposely cutting trace and repairing it afterwards or IF your soldering/dexterity is up to the task, 'gull-winging' the lead. IF lifted too high risks breaking off. Too little heat or trying to lift to soon, breaks trace; too much heat could result in damage to the trace/part. |
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Guest |
Posted: Sat Nov 08, 2014 10:19 pm Post subject: |
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Sadly IC706 is an SMD component afterall, so floating one point is not as easy as I would have liked it to be.  |
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jts1957 |
Posted: Sat Nov 08, 2014 12:58 pm Post subject: |
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You will need to 'float' a single IC pin.
Picture a 'dot' centered inside a 'circle' :
The 'dot' is the IC pin and the 'circle' is the PCB foil AFTER successfully removing the solder so they are no longer electrically connected together.
Pin 26 of IC706 is Output |
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Guest |
Posted: Sat Nov 08, 2014 10:34 am Post subject: |
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And checking the block diagram, then it looks to be the electronically controlled volume control. So IC706 is the bad guy here... Need to check the solder points as this is not an SMD component.
If these does not change anything then I will replace the item. |
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Guest |
Posted: Sat Nov 08, 2014 10:25 am Post subject: |
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Well, sadly the crackling noise is also in the headphones. SO now I need to go further back in the amp to find the trouble... Hmmm, damnit. |
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Guest |
Posted: Sat Nov 08, 2014 8:06 am Post subject: |
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I know. But I don't have a headphone jack at the moment. So I need to buy one before I continue.
Will get one later on today. But then again. Something must have been wrong there since the music now plays through the channel again. |
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jts1957 |
Posted: Fri Nov 07, 2014 10:44 pm Post subject: |
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You're going to a lot of trouble. If it turns out its crackling through the headphones, you will have done all that for nothing. |
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Guest |
Posted: Fri Nov 07, 2014 10:06 pm Post subject: |
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I have now replaced all the caps surrounding IC716 (OPAMP) and it helped some. Now music comes out in the right channel, and at the right level. BUT, the crackling sound and so on still persists. So I'm thinking that IC716 has some trouble also, so I'm gonna replace this to, just to have a go at it.
I have yet to test the Headphone jack, to see if the problem is there also. If not, then it could only be IC716 (OPAMP) that is faulty. |
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Guest |
Posted: Fri Nov 07, 2014 12:01 pm Post subject: |
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I will do a check of the headphone jack. If no noise there I'm pretty sure the problem is with IC716 as you say. I have looked over the entire block diagram, and as you say IC716 is the one that could be the trouble maker, and or the surrounding parts. Most probably the caps. |
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jts1957 |
Posted: Fri Nov 07, 2014 7:33 am Post subject: |
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You'll need to create your own places to divide the circuit. Today's surface mount parts and double-sided or multiple layered PC boards do not make this easy. Looking at the block diagram is easier, but finding a convenient point in the circuit to electrically separate items will be harder.
Does noise appear in the headphone? If not, IC716 discrete buffer, or a surrounding part could be bad.
Floating the FR input or output pin at IC706 may also divide the circuit. |
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