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Naim CDi servo board problem
Naim CDi servo board problem
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Old 8th July 2017, 06:52 PM   #21
Mooly is offline Mooly  United Kingdom
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Naim CDi servo board problem
You mentioned that with the VC line to the motor disconnected the motor doesn't spin. That suggests the motor board is OK and responds to an applied control voltage. You could rig up a 10 k preset (not critical, 10k, 47k, 100k, all are OK) across the rails of the motor PCB and then feed the wiper via a 10k into 'VC'. Altering the preset should alter the motor speed. I think its all working though.

I'm not quite sure what you done with the 5532 but you can not disconnect the actual input pins (to isolate them) because that will just cause the opamp output to swing to one or other of the rails. It would do that because it then runs 'open loop' with no local feedback wrapped around it.
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Old 8th July 2017, 07:33 PM   #22
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Originally Posted by Mooly View Post
You mentioned that with the VC line to the motor disconnected the motor doesn't spin. That suggests the motor board is OK and responds to an applied control voltage. You could rig up a 10 k preset (not critical, 10k, 47k, 100k, all are OK) across the rails of the motor PCB and then feed the wiper via a 10k into 'VC'. Altering the preset should alter the motor speed. I think its all working though.

I'm not quite sure what you done with the 5532 but you can not disconnect the actual input pins (to isolate them) because that will just cause the opamp output to swing to one or other of the rails. It would do that because it then runs 'open loop' with no local feedback wrapped around it.
Mooly I'm pretty sure adjusting the control voltage will change the speed. I isolated the 5532 not by disconnecting the feedback loops but the connection to the inputs (resistors).

Maybe the 7220 is not generating the clock signal? Can we test it without the scope? At the moment pin9 XSYS is giving out 1.7V
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Old 8th July 2017, 09:08 PM   #23
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By the way a ceramic capacitor in the NE5532 section 472K gives a reading of 4835pF with an ESR value of 18R. I dont have the chart for ceramic ESR but the value seems very high, could this be the root to the problem?
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Old 9th July 2017, 04:14 AM   #24
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Never mind its probably within its tolerable ESR value.
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Old 9th July 2017, 06:11 AM   #25
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Naim CDi servo board problem
A scope is essential kit really, especially for work like this. There is no realistic way to look at clock signals without I'm afraid. With something like this I would start going around every pin on the relevant IC's and make sure that what would be expected is actually there. The scope excels at that because you use it juts live a voltmeter, except now you can see any problems/noise and so on as well as missing signals.
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Old 9th July 2017, 07:39 AM   #26
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Mooly, just out of curiosity does pin 9 (xsys) on the 7220 have continuity with any other pins? On mine it does with just about all pins.
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Old 9th July 2017, 08:27 AM   #27
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Naim CDi servo board problem
On the Philips diagram I am looking at pin 9 goes only to the RF decoder chip. If your is different then this is another reason why its vital to have the correct diagram for your player.
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Old 9th July 2017, 08:41 AM   #28
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On the Philips diagram I am looking at pin 9 goes only to the RF decoder chip. If your is different then this is another reason why its vital to have the correct diagram for your player.
I tried but I couldn't find any info on the CDi schematic. I am more than happy to pay for it if anyone knows where to get one.

Looking at the ma inboard layout pin 9 goes straight to pin 26 (xtal) of the 7310. Since there are continuity to other pins (player on or off) I think that my 7220 circuitry is shorted. I'll order a replacement and see how that goes.
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Old 9th July 2017, 10:17 AM   #29
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Naim CDi servo board problem
If there is direct continuity between pins then that needs investigating although checking in circuit is problematic.

If the pins you suspect all carry different voltages when its powered up then they can not be shorted internally... might be a quick way of proving... although it doesn't mean the chip is not faulty of course.
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Old 9th July 2017, 11:39 AM   #30
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I'll desolder it, test it and will let you know how it goes. Cheers
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