CD player playing digital noise on a track full of silence

[akasaka]

I've posted this on a couple of other forums, but didn't really get a lot of opinions confirming or disproving my ideas, so please let me ask the same thing here.

Recently I've got a Nakamichi CD Player 3, the MusicBank kind. The seller said it was not opening the tray and thus playback was untested and they were giving it away for a decent discount. "Aight just a few new belts right?" — the famous last words before I turned my desk into a lab first time in a decade again.

Linking the service manual right here for those kindly playing along at home: https://elektrotanya.com/nakamichi_cd-player-3.pdf/download.html

So, indeed, first I went ahead and swapped the belts and lubricated all the plastic parts. One of the cogs in the optics lifter mechanism had some crud somehow make its way onto the rod so that had to be reseated.
Then it turned out the lever of the home position sensor of the stacker assy was broken off — so I bent the spring beneath it to account for that, finicky, but it works most of the time for now.
Powering it on revealed that sometimes it would glitch out, showing garbage on the screen or trying to spin the disc in reverse up to takeoff speeds. Tapping the +5V logic supply voltage regulator often fixed that by triggering a reset. So, reflowing that and the two transistors generating the ±5V supply for the DAC got the voltages steady and spot on within a few hundred mV of the designed value. (Those components went hot enough to slightly brown their surroundings on the board)

I took out a few caps at random on both the main and RF boards and they all matched the label, albeit I have to admit I didn't look at the ESR too much.
(Cue the Benny Hill chase soundtrack and footage of myself spending a whole day looking for the transistor shaped "turns-out-it's-a-fuse" that I've blown by shorting one of the caps by accident)

Then I plugged in my speakers and put in a pressed album and... the sound was absolutely trashed, as if only one bit of the DAC was working.
I assumed the DAC is broken, so I recorded a CD-R with a few sinewaves and a silent track, 30 seconds each.

And here's how the 1kHz sinewave, 50% FS looks like on the output:


Not quite 50%, neither a sinewave, but at least both channels are the same, so it's not like the DAC is faulty — I doubt both sides of it would've developed an exact same failure. It's more like something is loading garbage into it.

So I went on to play silence, and:


Definitely not silence either!

So, going on the path from the rear jacks backwards I traced along the following symptoms while playing the silence CD-R:

* Output filter and OpAmp: just repeats the noise that the DAC sends into it, once the DAC shuts up there's no noise, so it's ruled out
* DAC: sends out the abomination on the second picture above on the L and R outs, and the input data line gets some blips of '1' bits at times, while I assume silence should be all '0'? Sure enough, shorting the data in to ground makes it shut up. The output waveform is somewhat like this:
https://www.diyaudio.com/community/attachments/1677992232780-png.1149950/
* Digital filter / Resampler: Gets 1-2 of '1' bits every now and then on the data in line. Shorting the data in line to ground makes the whole downwards chain shut up, so I assume the Resampler is getting garbage data on the inputs.
* Sony DSP chip: the Subcode CRC incorrect flag line raises 1-2 times at a similar timing to those 1-2 '1' bits. (I don't have a second probe on the scope to compare). But I assume this is normal since the tracking has to catch up sometimes?
* All the other frequencies seem to be spot on, aside from the PLL — it's constantly 0.2MHz too high, but locks on to the specced 4.2ish MHz just fine once the CD is spinning.

In the end I have traced the whole path like follows:

RF output after the amp, measured on the RF testpoint (CN-105:3) while playing a pressed CD


EFM output from the amp as seen from the U102, taken at R170, with a pressed CD


The PLL clock, CN-109:2 (~PLCK signal), must be 4.2MHz as per the manual


Bit clock IN U801:17 (2.?68MHz in the manual) and Word clock IN U801:16 (44.1kHz in the manual): 24 bits per word, isn't it too much for 16 bit CD? or am I reading it wrong?


Bit clock IN and Data In (U801:18) while playing a silence track on a CD-R, to hopefully highlight the problem. We can clearly see 10 clock cycles are in a logical 1, whereas silence should be 0? Or is it some weird different format?


Bit clock IN and Data In while playing a music track on a pressed CD


Oscillator out (U801:4) to the DSP, 6.9244MHz in the manual


Data Left (U802:12) and Data Clock (U802:13) on the DAC while playing a silence track on a CD-R. This is data for the DAC so it clearly should be zeros and yet!


Data Right (U802:16) and Data Clock (U802:13) on the DAC while playing a silence track on a CD-R


So, my assumptions are:

1. The laser head, DF, DAC and OpAmp are not faulty
2. The Sony DSP CXD1167QZ chip (U102) is faulty

The CXD1167 is pretty hard to find in all of it's shapes and forms so if I'm right that might be a huge hassle, hence I would like your opinions on what else to check around here. Maybe I'm too dumb and all those waveforms just scream "Clean the lens (I did) and swap the decades old caps (I did not)!!"?

Thanks!

[shakalnokturn]

I don't think the CRC error flag should be active that often, anyway I came to the same conclusions as you did on the CXD1167.

Sometimes it is easier to buy a cheap working CD player of another model for parts rather than look for a specific component for retail. The problem is finding out which models of CD players may have the components you need.
There are lists regarding pickups and DACs, not so much information on the other components used.

[akasaka]

shakalnokturn

Thanks.
Sadly it seems the models using that kind of IC are pretty scarce (and as all players of that era, not really cheap).
I'll need to order a remote anyway and I found one IC in stock in the US, so maybe I'll ask a friend of mine to buy them and ship them over together.
It's also a -Q IC (not -QZ) which means it's a slightly different package. QZ ones are meant to be mounted from the underside and Q are the normal QFP ones. But I hope I can fiddle it in.

Upd: on a note of despair I went around reading random service manuals and found out that the CXD1125Q is pin-compatible for the most part. The "Test" pins on the 1167 are replaced with an external RAM port on the 1125. Given enough soldering acrobatics, and as long as their protocols are the same (good luck finding datasheets for those), it sounds like the unused pins could be lifted and soldered to an SRAM chip with wire :-)

I'll try to find a broken 1125-based player around here for cheap.

Here's the two side by side for reference:

[shakalnokturn]

That's going to be a fun repair experience, the kind I like, just because you can't give up.

The CXD1125 should be a bit more common, I've had to replace a couple of those over the years, one of which had a bad data line output to the RAM. If you're really stuck I can look in my unsorted (untested too) parts for a CXD1125, no promise, the last time I needed one it wasn't easy to find.

The Sega CD II uses a CXD1167 not that it's likley  to be easy or cheap to find. Also found in NAD 502, Dual CD-100RS, Kenwood DP-942.

[akasaka]

Sadly none of those seem to be common in Japan, and the DP-942 doesn't return anything from Google in general...

Most I've found for cheap on Yahoo are based upon the 1125 or something completely different

That being said I found a board on ebay for a similar Nakamichi model, and if the seller accept my offer that'll probably do the trick. Sure it won't be cheap, thanks to the USPS, but it'll take the burden off my mind for some time :-)

[wraper]

CXD1167Q is available on aliexpress https://www.aliexpress.com/item/1005004684109116.html . Most likely salvaged from e-waste.

[akasaka]

I've seen a few there and on ebay as well — the ebay one I fell for but it's been over 12 days and the seller sisitronic hasn't sent anything and won't even reply.

I've had questionable experience with parts from Ali in the past, from atmegas that have the timer go off randomly to outright empty shells without a die, so I'm kinda hesitant haha

[wraper]

You are hesitant to lose a few bucks but are ready to buy a whole player? With such sort of part IME you most likely will get what you order. An aliexpress if seller does not ship within allowed timeframe, order is refunded automatically. As of ebay, you should request order cancellation. If seller does not act, it will be refunded automatically.

[wraper]

You could also order from Utsource https://www.utsource.net/sch/CXD1167Q.html

[akasaka]

Now that I think of it, good call...
(Too many times in life I challenge whether I could without questioning whether I should)

Is UTSource a reliable supplier? If so, I'd rather go that route than ali (as long as they don't require me to be a company or something)
Thanks for the link!

P.S. I've taken a closer look at the ali link — the first pin is marked with a painted dot, while legit chips have it embossed. Is that enough of a sign to consider it fake?

[wraper]

They are a broker and have barely any of own stock AFAIK. My experience with them was good when buying NOS MCUs. But they also sometimes shipped counterfeit transistors and opamps from what I've seen on forums. Particular IC is a low risk item though, and it will become immeadeately obvious is something isn't right. In any case, there won't be better than that, you have no other choice other than buying from somewhat shady place. For production I buy parts from reliable sources like Digekey, Mouser, LCSC. But when sourcing something this old for repairs you must accept some risk if you want things get done.

[wraper]

P.S. I've taken a closer look at the ali link — the first pin is marked with a painted dot, while legit chips have it embossed. Is that enough of a sign to consider it fake?

Production can happen in different places, on different machines and can change over time even when made at the same factory. Also by nature of this IC, it's unlikely there will be any counterfeits that actually work. To get an informed opinion you need way more investigation than simply looking on a single IC and deciding that another one is fake because it does not look like yours. Also such pictures are only informative and should be taken with a grain of salt, it does not mean you'll get exactly like that. I personally would go with aliexpress due to much cheaper shipping.

[shakalnokturn]

If this is of any help:

I've just opened a Samsung  CD-42R. It uses a Samsung KS5990 DSP that looks, as far as I could be bothered to check, as if it could also be pin compatible-ish with the CXD1167. It has the RAM internal, but the PCB has provision for a different I.C. + external RAM.

Edit:

Well it turns out to be known as an equivalent:

https://partcross.com/semiconductor-manufacturers/Sony/4.html

http://ecadata.de/textsuch/zfindgnr.php?gnr=03.13.27.60.02.00.00&data=VRT&F_SPRACHE=2&NFIRST=0&TEXT=%B5P+%B5C+PC+round+about

[akasaka]

That's some interesting finds there!
Hmm that Samsung looks too similar to one of some cheaper brands I've seen here on Yahoo I think ...

But the ebay seller got back to me yesterday saying they shipped the part by simple untracked mail and so it should arrive in about a week or two, so let's see where that goes I guess

[wraper]

If this is of any help:

I've just opened a Samsung  CD-42R. It uses a Samsung KS5990 DSP that looks, as far as I could be bothered to check, as if it could also be pin compatible-ish with the CXD1167.

On quick glance looks more like CXD1125 except in also has built in RAM like CXD1167.

[akasaka]

So, today I received the 1167Q from sisitronic, and fitted it into the U102 spot.

What has changed:

- The 5MHz clock is on PCLK pins, so the insides of the chip are at least somewhat true to the label
- Otherwise the player won't even try to spin the disc... The laser seems to come on but no focusing takes place, no spindle action either.
- Then the player just gives up on reading the disc and ejects it

I'll probe around more later this week, but it's weird... I don't think I could've killed the laser diode by putting the whole mech assembly into a plastic bag to keep it from dust while waiting for the chip?

It's as if some command or something isn't coming through.

A crazy theory would be that they sent me a relabeled 1125 and it's now confused with all the RAM lines attached to GND, but the chip doesn't look relabeled.

[wraper]

A crazy theory would be that they sent me a relabeled 1125 and it's now confused with all the RAM lines attached to GND, but the chip doesn't look relabeled.

It's not crazy at all. Try rubbing its marking with acetone, some other strong solvent or 95+% IPA or ethanol if you don't have any better

[akasaka]

Tried that, the marking won't go anywhere, so I assume either the soldering I did is shit or another short of the power supply I accidentally did during initial testing killed something down the line — I'm not seeing any command/data exchange on the system bus between the mechacon/brain/cxd, even though the display seems fine and loading/ejecting discs works perfectly as before. I'll tackle it more a bit later or just stuff the whole thing to some other poor lad thinking they can ever repair a nakamichi! :p

[rhb]

This may sound silly, but trust me, I've "repaired"  several $1000 of kit by scrubbing the boards with liberal quantities of 91% isopropyl.  You should rinse it several times with fresh IPA and dry it carefully to get rid of the trace water.  I use a hair dryer.

Solder flux is hygroscopic and absorbs moisture from the air.  This leads to stray leakage paths that mess with low level signals.  Success is determined by being able to reach the PCB with a soft toothbrush.  My CD player took two cleanings because there was flux under the MCU flat pack.  But after the 2nd pass it's been working fine for several years.

Good luck,
Reg