Sony CD Walkman / Discman D-E401 & D-EJ621 - Won't detect disc - Page 1
Forum section: electronics / repair

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: March 19, 2025, 02:07:57 pm
content: Not sure what to do about those two. Both perpetual "No Disc".The E401 is in visually good condition, minor battery contact corrosion that I repaired. Nothing on PCB/drive. The sole SMD aluminium electrolytic cap measured with borderline ESR, replaced. Laser is turning on, focus servo does a search, spindle motor spins up (the speed they usually spin during detection, but slower than during reading of ToC / inner tracks), sled returns to inner position. This set has Focus Gain / Tracking Gain pots, adjusted in a wide range, makes no difference. Tried increasing / decreasing laser power, no difference. Tried different CDs. Cleaned lens, no difference. Looks like lens might have some scratches, hard to tell. Tried different discs, spindle condition and placement is good, should absolutely be in range for the focus servo. Reseated the pickup flex multiple times, cleaned with IPA, no visual damage. Can't find service manual for this one, only the somewhat similar 44X series.The EJ621 has no visible damage besides a pushed down spindle and some minor battery contact corrosion. Fixed battery corrosion, nothing on PCB/drive. Used a working model as reference for the spindle height. Spindle has good retention, no major oscillations. Oiled spindle motor. Cleaned lens with Q-tip & IPA, multiple times, no scratches I can see. Laser is turning on, focus servo does a search, spindle motor spins up (the speed they usually spin during detection, but slower than during reading of ToC / inner tracks), sled returns to inner position and keeps bottoming out (IIRC the 401 has a switch and this is one of the newer players that just keeps bottoming out). Reseated the pickup flex multiple times, cleaned with IPA, no visual damage. Had to put some force on the flex to get it off the adhesive on the PCB when doing drive maintenance, seems Ok. Tried increasing / decreasing laser power, no difference. Tried different CDs. No manual tracking / focus adjustment pots on this player. Service manual has no information besides eye pattern check, don't think that would help, what would I do if it isn't good, no adjustments.No replacement parts available and I don't know how to diagnose or repair problems in the actual pickup.

author: drhex
author_rank: Regular Contributor
timestamp: March 19, 2025, 05:28:42 pm
content: Iirc, the focus is achieved by the return signal being ovalized one way or the other when out of focus. This ovalization is measured and minimized, signal should be measurable. Does it achieve focus or is it just going up/down a few times and then stops?

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: March 19, 2025, 06:04:02 pm
content: Both players do the usual dance where they turn on the laser, move the focus servo up and down, keep moving the pickup towards the center, repeat, spin the disc occasionally etc. Haven't measured anything with a scope on those. It's always a bit of a PITA since I don't know how I'm supposed to actually get scope probes on the test points during operation, I always have to solder wires to them. The 401 has a test mode and some adjustments, so there might be something I could do, with the 621 there are no such things. I assume neither of the players actually gets the disc in focus, otherwise they should start to ramp up the spindle speed, shouldn't they? The service manuals for the older players sometimes have helpful information, the newer they get the less there is, basically only useful for the schematics / board views and some nominal voltages on the ICs. I haven't been able to find much information on the pickups, even how to properly dissemble them and what would I even do if I determine that say the diode array is broken. The PCBs and capacitors seem to be in good condition, so I didn't try to do any troubleshooting on that as I don't suspect things like corroded vias, leaked caps, shorted transistors or something I could repair without unobtainable replacement parts. I did a lot of googling and found very little helpful information for more advanced issues with these players.Edit:Just to be clear, these players do the exact same search procedure even if there's no disc in the drive. Not sure why they would spin the disc if they haven't found focus yet, which they obviously can't since there is no disc. Also always wondered why they move the sled towards the center in that case, my theory is in case there's an 80mm disc in there? I also don't quite understand how the newer players know when they hit the center with the sled. On older players there's a switch either on the drive or the pickup, newer players don't have that. There's no end to what I don't know about these things, wish there was some good reading material so I could repair the more advanced issues :/Edit2:You can actually buy a replacement pickup for the drive in the 621:https://www.aliexpress.com/item/1005005625497671.html

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: March 20, 2025, 09:02:01 am
content: Is there a better place to ask these questions? I haven't really found any quality material online about Discman repair. Would love to learn more, but it seems there's just not much out there

author: coromonadalix
author_rank: Super Contributor
timestamp: March 20, 2025, 09:40:11 am
content: find diskman or any cd players services manuals and they'll show you how to service themyou need to see the laser pickup signals and the focus ok signal, if not the laser head is dead electronically or mechanicallySony and other brands had big problems with lens suspension, over the years it failed and the electronics could not handle iti have repaired tons of them, i was working in a service centerthe laser pickup is moved to the center to see the track zero, its the index content of the cdit moves the head up and down a few times to see its presence and do a focus ok, if not it simply stop, some can retry x timessome brands have service mode to continue to spin and do a forced read, that way you can adjust things, even laser power outputi think you need to learn many things ? instead of doing this or that you need to see the head signals, a laser will age and die over the years

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: March 20, 2025, 10:00:37 am
content: Quote from: coromonadalix on March 20, 2025, 09:40:11 amLike I said, the service manuals for CD Walkman from a certain point onwards contain nothing useful besides schematics / boardviews and some nominal voltages, they most certainly don't explain anything about repairing / servicing.Quote from: coromonadalix on March 20, 2025, 09:40:11 amIs there anything you can do to fix a pickup? Haven't seen anything on taking them apart / reparing them. Even if I can diagnose them as dead, I don't have replacement parts. There are a few types of pickups you can still buy at fairly high prices, not useful for most players. If I have a donor unit I can diagnose just by swapping.Quote from: coromonadalix on March 20, 2025, 09:40:11 amObviously, but why does it do that even when there's no CD in the drive and it can't even achieve focus? Why does it try to spin a nonexisting disc?Quote from: coromonadalix on March 20, 2025, 09:40:11 amI think it moves the sled inwards to detect a smaller disc, at lest that's the only explanation I can come up with. Keeps moving inwards on the newer players as there doesn't seem to be a way for the pickup to detect it reached the end, no switch?Quote from: coromonadalix on March 20, 2025, 09:40:11 amThe older Sony players have a test mode, it's quite useful. I've only found a single model out of dozens that actually has adjustments in service mode, seems uncommon with Discman!Quote from: coromonadalix on March 20, 2025, 09:40:11 amI do, unfortunately like I said there's very little information out there and a lot of stuff I found online in forums etc. is either clearly wrong or just surface level information.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 20, 2025, 11:13:46 am
content: Obvioulsly with due respect i think eevblog will not help you to understand a few things as it seems1st you don't understand how they works ... and i think you want fast answerseven with no disk the pick up will go the the start / center and will do it's focus ok thing, it's a presence detection, and most of the cd players / dvd players spin the disk, i've seen only 1 model who don't spin, and it is not a matter of disk sizebuy the laser pickup and you'll see, it may simply work ... they where relatively adjusted good, needed some more precise adjustments once in the systemthat's now obvious ... sorry, but the way you wrote and answer does not give the vibes you're open to some answers, you sound stubborn, i wont reply or add anythingi was an audio tech for many years, audio, video, broadcast ...good luck

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: March 20, 2025, 11:59:35 am
content: Quote from: coromonadalix on March 20, 2025, 11:13:46 amThe issue isn't that I'm "stubborn" or not "open to some answers" it's simply that you haven't answered a single of my questions. It appears you haven't even read them. I didn't ask if all players do the presence detection that way (they do, I know...), I wanted to learn why it works that way. i.e. why spin the disc and move the pickup if you can't even find focus? And all the other stuff I've asked, pickup disassembly and repair, Genuinely curious. "1st you don't understand how they works ... and i think you want fast answers" - I said that myself, I'd take ANY answers, information I can digest. I'd love to learn more about these players, but, like I said, I can't find any good resources, service manuals are bare bones and contain nothing about function or repair procedures, the forum discussions I've found are not very helpful, etc. Fantastic that you were "an audio tech for many years", would've been nice if you had actually shared some of that information instead of calling me "stubborn" for some arbitrary reason and bragging about your expertise. No information, only snark. Enough 'forum' for me for a while, I regret that I even asked.