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Old 3rd May 2016, 10:12 PM   #1
napovo is offline napovo  Canada
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Default Rotel RCD855 no output

Hi all,
I am newbie here and I need your help. I've purchased a Rotel RCD855 from a museum sale. Plugged it on with a CD, the machine is reading the TOC. All the buttons functions work, but there is no sound from neither Analog or Digital output.

Can you help me to diagnose the problem and fix it please?

Thank you very much,
Napo
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Old 4th May 2016, 07:46 AM   #2
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You say it reads the TOC, but does it actually Play? ie, does the Time 'tick' along?

Have you any Electronics experience, what Test Gear have you available?

Service Manual here.................
Rotel RCD-855 Manual - Stereo Compact Disc Player - HiFi Engine

Looks like it uses the TDA1541 DAC IC, nice, are you able to oscilloscope the DATA and Clocks going into this IC?
It has several Power Supplies, can you measure these with a DVM for us?
The Analogue then goes into two Op-Amps, U401/U402, these are fed by +/-15V, can you check these? I think the problem will lie elsewhere though as you say the Digital Out is not working also.
This is derived from U (108?) (The Manual isn't scanned very well) the SAA7220 Pin 16. Can you measure the Supplies and DATA/Clocks on this IC?

P.
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Old 4th May 2016, 01:59 PM   #3
napovo is offline napovo  Canada
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Hi,
Thank you Percival for your input.
- Yes the tracks are working with time counting along on the display.
- I am a newbie DIY and I have only a Multimeter with me now.
- I never use the oscilloscope yet, and I dont know what can it do, but I can try to buy local one
- I will try to find from the service manual and will back to you, hope you will continue to help me.

Thank and regards,
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Old 5th May 2016, 07:23 AM   #4
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Ok, lets not worry about the 'scope just yet then.
With your Multimeter can you measure the Supplies to U108 (SAA7220)? Let's start there.

P.
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Old 5th May 2016, 09:26 PM   #5
napovo is offline napovo  Canada
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Hi Percival,
I am reading the Service manual to find the supplies to the U108. The scanned SM is too dimmed that I cannot understand or guess what it is.
Could you tell me which pins are the supplies? I attached the scanned U108 here for your reference.

Thank you for continue helping me. I am really interested to find out and learning this CDP.
Napo
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File Type: png U108.png (172.0 KB, 53 views)
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Old 6th May 2016, 12:19 AM   #6
napovo is offline napovo  Canada
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I've just measured the voltage between pins 2-3 of the U401, U402. They both show 0V, either AC or DC.
- Are the pins 2 and 3 the supply voltage for the U401, U402?
- I see they have 6 pins, but on the manual only 4 pins (1-4). Do I miss smth?
- Can you tell me how to check the supply of TDA1541 and SAA7220, how much the voltage should be?
Thank you and please keep update.
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Old 6th May 2016, 12:20 AM   #7
napovo is offline napovo  Canada
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Default U401-402

here is the extract of the U401 and 402.
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Old 6th May 2016, 03:41 AM   #8
napovo is offline napovo  Canada
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and the U301-TDA1541A. Tks
Attached Images
File Type: png U401_402.png (73.4 KB, 51 views)
File Type: png U301_TDA1541A.png (183.8 KB, 48 views)
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Old 6th May 2016, 12:04 PM   #9
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Quote:
Originally Posted by napovo View Post
I've just measured the voltage between pins 2-3 of the U401, U402. They both show 0V, either AC or DC.
You will not measure anything with a Meter here, these are the inputs of the IC. They are NE5532's which are 8 Pin IC's. Their Supply Pins are 4 (Negative Supply) and 8 (Positive Supply). You should expect Pin 4 to be -15Volts and Pin 8 to be +15Volts.
- Are the pins 2 and 3 the supply voltage for the U401, U402?
- I see they have 6 pins, but on the manual only 4 pins (1-4). Do I miss smth?
- Can you tell me how to check the supply of TDA1541 and SAA7220, how much the voltage should be? The SAA7220 looks like it has only one supply, on Pin 24 which should be +5Volts. The TDA1541 has several Supplies.
Pin 15 = -15V
Pin 26 = -5V
Pin 27 = +5V

Thank you and please keep update.
If you can check those Voltages and report back, that'll be a start. If you could also check the Voltage on the KILL line. The Bases of the Muting Transistors. If these are being turned on then that would produce no O/P.
After that we really need to see what sort of signals are present and that would involve an oscilloscope I'm afraid.

P.
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Old 6th May 2016, 04:18 PM   #10
napovo is offline napovo  Canada
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Hi,
I have measured some supplies:
U401 and U402 (NE5532)
- Pin 4: -15v
- Pin 8: +15v

U301 (TDA1541)
- Pin 1: +2.5v, while the manual says +5v
- Pin 15: -15v
- Pin 26: -5v
- Pin 27/28: +5v

U 108 (SAA2720)
- Pin 24: +5v

So the only difference to the manual is the pin 1 of TDA1541 which is only +2.5v

Please advise, thank you!
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