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Old 24th May 2006, 09:41 PM   #1
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Default The Denon DCM Series CD Player Repair Thread

Since so many of these inexpensive players seem to have a high rate of failure, I thought it would be a good idea to have a thread dedicated to their repair.

I'll start with the player I'm currently repairing . I bought a DCM-370 from a seller who openly disclosed that the player needed repair. When it arrived, it would play bits and pieces of audio throughout a disc, with a lot of long-distance skipping. After attempting to clean the lens, lubricate the gears, etc., etc., the problem didn't improve. Actually, the more I used it, the less it played until it eventually couldn't even read the TOC.

Knowing that most instances of these problems were solved either by replacing the laser or the sled / spindle motors, I elected to purchase a whole new assembly (pickup, mechanism, everything). When I put it in the player and tried it out, it wouldn't spin the CD. I figured the spindle motor on the new assembly was dead. To confirm it, I took the new laser and put it on the old assembly. Still no spin. I thought this was odd, so I put the old laser on the new assembly, and lo and behold, the disc spun! However, it made the same clicking noises it had when it was on the old assembly and failed to read the TOC.

Any suggestions?
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Old 26th May 2006, 02:28 AM   #2
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Default Now With Pictures! (56k death)

Larger images available upon request.

Here are a few pictures which show some of the stages of disassembly of the DCM-370:

Cover removed, circuit board on
Click the image to open in full size.

Cover removed, circuit board off, flex cables removed
Click the image to open in full size.

Circuit board close-up, note DACs
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Back of carousel, full view inc. optical pickup
Click the image to open in full size.

Back of carousel, optical pickup close-up
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Back of carousel, optical pickup removed, flex cables removed
Click the image to open in full size.

Optical pickup / mechanism by itself
Click the image to open in full size.
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Old 26th May 2006, 02:53 AM   #3
anatech is offline anatech  Canada
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Hi infinitesymph,
Isn't that a standard Sony Mechanism? The head looks like a KSS-240A or variant.

The only high rates of failure I've seen is when people use the Random (read DIE) button. That tends to tear up the spindle motor. If it's "knocking" the bearing in the spindle motor may be shot. Look at the gear track on the side of the head for bits of nylon that may come from the gear (small section). Also check that the CD isn't hitting the edge of the tray.

If you have a 'scope, watch the eye pattern.

-Chris
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Old 26th May 2006, 08:12 AM   #4
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Default Laser Woes

anatech: Thanks for the reply!

You're right, it's a Sony KSS-213C laser which is quite common and has many cheap replacements. I opted to replace the whole mechanism (KSM-213CCM) instead of troubleshooting the Mabuchi motors individually.

The spindle motor dying was my initial thought, since I'd heard technicians say that the rate of laser failure is lower than what most people think. However, even with the replacement assembly, neither laser was able to read the TOC.

I tried all variations of lasers and assemblies:
1. new laser + new assembly = no spin
2. new laser + old assembly = no spin
3. old laser + new assembly = spin, but no read
4. old laser + old assembly = spin, but no read

So, in both cases, the spindle motor didn't spin the CD when the new laser was in place. Perhaps the new laser is DOA? To be safe, I'm shipping it back for a replacement.

Are there any tracking/focus adjustments on these lasers? I know there's a laser power adjustment near the entry point for the flex cable, but power doesn't seem to be the issue (and I've tried adjusting it with no noticeable results).

Another question: In the picture of the circuit board, near the bottom are what appear to be two adjustable potentiometers. The circular near the flex cable reads "PIO1" and the other looks like "TIO1." Any idea what these might adjust?
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Old 26th May 2006, 08:12 AM   #5
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Default Movie - DCM-370 Skipping

I recorded a brief movie of the problem in action a few days ago.

Link, video portion requires DivX codec

The background noise is an old computer humming, but one can clearly see and hear the pickup trying to track. Sorry about the poor lighting; my flashlight was almost dead. Maybe this will give a better idea of what the cause might be.

-Jameson
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Old 26th May 2006, 12:51 PM   #6
anatech is offline anatech  Canada
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Hi Jameson,
That looks like the E-F balance is off. Touchy adjustment. The lighting was terrible!

Get the manual from Denon. They are not expensive. Do not touch the pots on the laser head. I do sometimes, but I have a lot of experience doing this. It is very easy to make things worse. I may touch up the E-F balance from time to time. Never the power.

Buy a new flex cable (white flat thing). It should not cost much.

Check the turntable height on the mech when you get it. They tend to slide downwards if they go anywhere. Your old mechanism is more suspect that the new one.

You really need an oscilloscope and test discs to troubleshoot properly, but Denon builds in a test program (Thank you Denon!!). You may get some clues trying this. It is intended to be used with a standard disc. CA1094 or similar if I recall correctly. Servicing CD players is normally enjoyable for me. I love squeezing that last bit of performance out of them.

-Chris
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Old 26th May 2006, 06:31 PM   #7
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Default D'oh

E-F balance, eh? That's bad news, considering this was meant to be a budget purchase .

The service manual seems to be about $25 from Denon, with $10 for the flex cable. Even then, I don't have an oscilloscope or test CDs. Keep in mind my initial investment in this player was $15! So far I'm at $50 (player + soldering equipment + new laser assembly), which isn't bad, but it's also true that a used DCM-370 in working condition goes for about $60-$70. I guess it might develop these same problems over time, though.

If I promise not to blame you when I screw up the CD player, will you tell me where the E-F balance adjustment is located?

I'd consider sending it in for service if it was a more robust or expensive player, but if I can't fix it myself, it probably won't get fixed.

-Jameson
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Old 26th May 2006, 06:59 PM   #8
anatech is offline anatech  Canada
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Hi Jameson,
Deep breath now.

The E-F Balance is on the head (on a 240 anyway). So it's either a defective head or it could possibly be the flex cable.

I do not have the manual for your machine or I'd instruct you more exactly. But you do need a 'scope and test disc to perform the adjustment. You need the manual to start the test mode (can't remember on this one) and step through the program.

The value of the machine is relative. It has a good mechanism for one, the were fairly problem free (up here) for two. That's your call. I'd be fixing it without thinking about it too much if it were mine. You do not have the troubleshooting skills or equipment to narrow down the problem without buying a little extra.

-Chris
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Old 27th May 2006, 12:21 AM   #9
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Default KSS-213C and KSS-240A

I see you're a big advocate of replacing the flex cable from the pickup to the circuit board, so I went ahead and ordered the appropriate replacement (Denon part #: 9580024400). I'll wait to try anything new until the flex cable and the replacement assembly arrive.

Until then, I thought I'd ask about what the single potentiometer on the KSS-213C might be for, since the KSS-240A appears to have three.

Here are some pictures for comparison:

KSS-240A
Click the image to open in full size.

KSS-213C
Click the image to open in full size.

Is the single pot a simplified adjustment?

-Jameson
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Old 27th May 2006, 12:32 AM   #10
anatech is offline anatech  Canada
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Hi Jameson,
I honestly don't know what it's for. I would have to search around for that info. Could be laser power, which is historically mounted on the head. Focus offset and E-F Balance may be servo corrected in the new machines. This means there are no adjustments that you can make.

I see from the main board picture that this is the case.

-Chris
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