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B&O CD-6500 Destroyed After NOS Mod?
B&O CD-6500 Destroyed After NOS Mod?
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Old 26th June 2018, 01:55 PM   #1
phildela is offline phildela  England
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Default B&O CD-6500 Destroyed After NOS Mod?

Hi guys,
I bought a B&O CD-6500 on a whim that was faulty, got it working with a set up. It was working flawlessly and sounding fantastic (best TDA1541A based player I ever heard). I thought I would NOS it as I've done on many players in the past, but to my horror it would no longer read TOC! I tripple checked my work and all seemed correct. I removed the mod but unfortunately it still wasn't reading TOC. I have checked all joints, tracks and connectors, all voltages are normal, the laser is lit and the disk spins as it attempts but fails to read TOC. I checked the HF and it looks like there is a normal signal which collapses when the player gives up. All signals seem OK (in my limited experience) around the chips except for pin 3 data on the filter (SAA7220) which looks strange.
I can't seem to get another 6500/5500 to use as spares and I am contemplating getting a faulty TDA1541 chipset player to use for parts as I suspect the SAA7210 or SAA7220.
Anybody got any ideas on this? It is a really nice sounding player and I would love to fix it.
Thanks for your help!
Phil
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Old 26th June 2018, 04:31 PM   #2
lcsaszar is offline lcsaszar  Hungary
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Signal at pin 3 strange indicates that the issue comes from the SAA7210. That should be I2S data, difficult to evaluate on oscilloscope. I rather suspect a servo misalignment. You could try the factory calibration procedure according to the service manual.
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Old 26th June 2018, 08:23 PM   #3
phildela is offline phildela  England
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It could be either chip, but since I linked pins 1, 2 & 3 on the 7220 to 1, 2 & 3 on the DAC - I would possibly suspect the 7220 first. I have tried adjusting laser current and Focus Offset to no avail; here's what it looks like - maybe thats normal but it looks clipped and noisy to me. The clock and other datas normally rise to double that height.
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Last edited by phildela; 26th June 2018 at 08:25 PM.
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Old 27th June 2018, 09:36 AM   #4
lcsaszar is offline lcsaszar  Hungary
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Quote:
Originally Posted by phildela View Post
It could be either chip, but since I linked pins 1, 2 & 3 on the 7220 to 1, 2 & 3 on the DAC - I would possibly suspect the 7220 first. I have tried adjusting laser current and Focus Offset to no avail; here's what it looks like - maybe thats normal but it looks clipped and noisy to me. The clock and other datas normally rise to double that height.
Normal since you have double load. What if you remove the 7220? This is what I did: unsoldered the 7220 and soldered a 28-pin IC socket to its place. Then I bridged the 3 input pins to the 3 output pins with rigid wires. And moved the oscillator (external oscillator circuit) to the 7210. Something I did also with the muting.
But I think all these are not related to your problem, which is most likely the servo is at the extreme of the focus pull range. Check the turntable height also.
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Old 27th June 2018, 09:17 PM   #5
phildela is offline phildela  England
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Thanks for the advice - I have a working Rotel RCD-855 which I can probably swap parts out of. The CDM4/11 doesn't seem to have a turntable adjustment. I have got a different CDM4/19 but its not the 4 pole motor type. What pins do I connect to what on the SAA7220? What is the advantage of running without a filter (never tried that).
Cheers,
Phil
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Old 28th June 2018, 12:19 PM   #6
lcsaszar is offline lcsaszar  Hungary
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Join Date: Mar 2004
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Running without SAA7220P/B digital filter is called "NOS modification". Many prefer it, others not, you have to try. Here is how I did it:

NOS mod
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