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Naim CDi servo board problem
Naim CDi servo board problem
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Old 5th July 2017, 12:08 PM   #11
Mooly is offline Mooly  United Kingdom
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Naim CDi servo board problem
Its not proof enough I'm afraid. The clock should be easy to check with a scope.

Trace the motor leads and see what drives it. Something like an L272 (dual power opamps) perhaps or maybe discrete ?
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Old 5th July 2017, 02:18 PM   #12
iqpi is offline iqpi  Australia
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There's a motor board attaches to the motor. The motor board has four wires to it. Vc, Grnd, -8V, 8V printed on the board, I've measured:
Vc : 4V
Grnd : -
-8V : -10V
8V : 10V

I think the Vc is a Voltage Control that tells the IC (LM324N) on the motor board whether to speed up or slow down the motor since the voltage is at constant 4V and the speed of the motor is constant.

I took the Vc pin off and now the motor is not spinning, could this be the voltage that tells how fast the motor should spin? Mayve we work backward from here and see what is giving the 4V signal?

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Old 5th July 2017, 04:10 PM   #13
iqpi is offline iqpi  Australia
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I might have something.

The connector to the motor board has Vc connected to the NE5532N (as pictured). The NE5532N has 2 outputs from pin1 (1out) and pin7 (2out).
This is the measurements of the pins with power on:
1 (1out): -4.3V
2 (1in-): -
3 (1in+): -
4 (Vcc-): -10V
5 (2in+): -
6 (2in-): -
7 (2out): 4.3V
8 (Vcc+): 10V

So pin 1&7 has constant power out. The power out from pin 1 (-4.3V) got cancelled to 0V by the pin7 (4.3V) at resistors in blue stripes. The 4.3V from pin7 of course went on to the motor board via Vc pin.

I thought the laser has to focus first and if there's a disc present then the spin signal will be sent to the IC but this IC seems to putout constant +- 4.3V no matter what. Is the NE5523N is fried or is there something more sinister at play?

Aaron

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Old 5th July 2017, 05:51 PM   #14
Mooly is offline Mooly  United Kingdom
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Naim CDi servo board problem
Yes, VC will be the control voltage.

It would be unusual for an opamp (the 5532) to fail, and the voltage readings seem logical in that neither output is stuck at a rail voltage. It looks like one opamp is used in inverting mode switching either a +4.3 to -4.3 or vice versa.

So I guess either pin 1 or pin 7 feeds the motor drive amp. Whichever it is, the other side of the opamp will be receiving the drive voltage from the system control but depending how the opamp is configured you may well not see a meaningful voltage on either input of the opamp.
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Old 5th July 2017, 05:59 PM   #15
Mooly is offline Mooly  United Kingdom
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Naim CDi servo board problem
This isn't the right circuit but the idea is the same. Pin 7 would be your VC line and the input is the MC line at the right.

It might give you a clue where to look next. The opamps in yours and in the diagram could be reversed of course.

Remember this is only an outline of a typical circuit. You would need to identify the input and see if the motor responded to a change in voltage at that point.
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Old 5th July 2017, 06:28 PM   #16
iqpi is offline iqpi  Australia
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Mooly are you suggesting that the system control is sending the signal to the opamp for constant +-4.3V output? Is there anyway to check the opamp without taking it out?

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Old 5th July 2017, 07:10 PM   #17
Mooly is offline Mooly  United Kingdom
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Naim CDi servo board problem
I'm thinking its more likely the Syscon is telling the motor to spin rather than a faulty opamp.

Opamps behave predictably but its essential to have the circuit diagram to refer to and so see what is to be expected. The two inputs per opamp should normally have the same DC voltage present (whatever that may be in the application).
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Old 6th July 2017, 05:24 PM   #18
Salar is offline Salar  Germany
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On an earlier Philips CD-304MKII (SAA7210 Decoder / SAA7220 Oversampling Filter) i made the observation that unplugging the Display Board from the servo board (and by this, also diconnecting one of two controller ICs) made the disc motor spin. Maybe some communication line with the conroller is missing as well?
All the best,
Salar
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Old 7th July 2017, 10:01 PM   #19
guido is offline guido  Netherlands
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Probably clock related. Check if the 7220 generates the clock signal towards the 7310 (XSYS).
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Old 8th July 2017, 05:54 PM   #20
iqpi is offline iqpi  Australia
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Guido, Pin 9 of the 7220 gives about 1.7V so I guess it ok?

Salar, both 7220 and 7310 is on the main board in mine.

I've isolated the NE5532 op amp from any inputs except for the Vcc+ and Vcc- but the problem still persist. I've even replaced the NE5532 and the LM324 four the transistors (although the old one tested ok) on the motor board but still no cigar.

What do you guys think? The problem lies with the motor board? or the main board?
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