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Old 21st September 2008, 02:53 PM   #1
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Default Disc spinning too fast

Hi,

I am hoping that someone can point me in the right direction to sort a problem with my Rotel RCD965BX.

I have just put it back together after doing the mods listed below. (I know that I should have done them in stages, but the 965 is such a pig to take apart and work on that I did them together, checking each stage as I did.)

The problem is that after about two or three minutes of playing flawlessly, the disc starts to spin very fast, then stops and spins counter clockwise, also at high speed.

When I turn the player off, wait a few moments and start it up again it plays flawlessly and then starts to spin after a few minutes. When spinning like this, the player does not respond to the stop button but respond to the eject button

I have not done any mods to any of the servo chips or the power supply to the mechanism, thinking I would do that later.

The mods I have done are:

* Installed a Tent XO clock with its own PSU and regulator, which I had been using in a TDA1543 DAC (where it worked fine.)

* Changed the op-amps, added a separate transformer, new smoothing caps and regulators for the op amp.

* Changed the digital supply 5V regs to LM317/337. These all checked out OK.

* Removed the muting resistors

* Following the mod advice on the huge Marantz CD63 & 6& thread, I have replaced the 47uF elctro/47nF ceramics caps with 100uF Os-con/100nF/X7R on the SAA7220 filter and SAA7310 decoder and the MC68HC05 microcontoller.

* Replaced the supply line series resistors on 5V digital supplies with a choke and ferrite beads. I also did the choke mod to the + and - digital and analogueSAA7232 DAC chip supplies, but left the existing Black Gate caps in place.

Why does the player work so well for a short time and then go haywire. What shoudl I check?

Any suggestions?

Joe
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Old 21st September 2008, 03:19 PM   #2
poynton is offline poynton  United Kingdom
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Disk spinning like this is usually a symptom of a clock problem.

Check carefully or revert to original clock.



Andy
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Old 21st September 2008, 03:56 PM   #3
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Hi Andy
Quote:
Disk spinning like this is usually a symptom of a clock problem.
Check carefully or revert to original clock.
Hi Andy,

Thanks for your reply. I had read your advise to check clock on one of your previous response to another members mechanism problem and so that was one of the first things I did, as well as check all the voltages twice. Nothing untoward.

Just after I posted my distress call, I remembered reading something on the Marantz CD63/67 megathread about the laser ribbon cable and its refitting it properly. I took the ribbon cable out and reseated it. The problem was worse and now the motor oscillated back and forth and wouldn't read TOC, nor would it respond to any of the control buttons.

So, went back to the cable and reseated it again and - problem gone. The player has been working flawlessly for the past 30 minutes and with different CDs. Does all the open, stop, skip, pause, play, track stuff like its supposed to.

So I guess that ribbon is a trap for unwary players.

By the way, thanks for your input on the Marantz thread. So much of the advice and mods are applicable to the Rotel. Now that I have gotten over this scare, my is to separate the analogue and digital 5V supplies and put a regulator on each chip. I will add another transformer and to power these regs.

Cheers,

Joe
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Old 21st September 2008, 04:01 PM   #4
poynton is offline poynton  United Kingdom
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One mod at a time ?????


Andy
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Old 21st September 2008, 04:16 PM   #5
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Quote:
One mod at a time ?????
From now on, one mod at a time.

The problem with the Rotel is that it is a monoboard sandwiched between the mechanism and the case. To work on the board I have to dismantle the whole thing. Every time I do that, the ribbon cable has to be taken out and reseated.

But, yes, one mod at a time. I think I was lucky this time. With a single mod you know where to start if a problem arises.

Joe
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Old 22nd September 2008, 02:54 AM   #6
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I spoke too fast.

This morning I switched on and inserted a disc which played no problems. Within about 3 minutes the disc started to spin quite fast. So I switched off, waited a minute and started again. Same problem after about a minute.

This time I pressed stop, and it stopped, pressed play and it started and has been playing flawlessly for the past half hour.

I have been thinking about the possibility of clock problem, but this Tent XO module has been working in an 8 x TDA1543 DDDac for a while. I just transferred it to the Rotel, although I did build a new PSU and the regulator shown on the Tent website. All the clock supply voltages are spot on and the thing works.

Now, here's a new twist. I just went and changed the CD in the player, and when the drawer retracted the disc just spun to a high speed. Pressed stop and it did. Then play and its working fine again.

And another intersting thing. On Jennifer Warnes "The Hunter" track 8, "Way down deep," which has some very deep bass, the player emits a sort of static sound, in time with the bass, and then begins the fast spin routine.

Any ideas?

Joe
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Old 22nd September 2008, 03:50 AM   #7
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Something else to report. I accident;y knocked the player while a disc was playing and got that static sound. It was almost like knocking a vinyl player and the arm skipping. Then the player seemed to lose the plot and started that spinning clockwise and counterclockwise thing that it has been doing.

Does that point to something to do with the laser reading te disc? Perhaps not adjusted properly after the mods?

Joe
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Old 22nd September 2008, 11:33 AM   #8
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Quote:
Disk spinning like this is usually a symptom of a clock problem.
Check carefully or revert to original clock.
Andy,

It seems you were right to begin with. It was the connections from the clock PCB which seemed to be an intermittent dry joint. When I gently tapped the clock PCB, which is connected by two pins to the main PCB, the player went berserk and did the whole fast spin thing. So, I re-soldered the two connections and viola! All okay. No response when I tap the clock PCB and I can't induce any of those previous disc problems, even with a good sharp rap on the player.

Perhaps the jiggling of the main PCB when I re-seated the laser ribbon cable, which I thought had cured the problem, just re-seated the clock PCB pins for a while.

Anyway, it has turned into a good, if humbling, learning experience. I have been into DIY Hi-Fi for more than twenty years and this is the first time that that I had let a dry joint escape my notice.

Cheers,

Joe
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Old 22nd September 2008, 01:02 PM   #9
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A few tips on cdm maintenance to ensure a long (and prosperous ) life of the player:

Those old cdm4 players don't like a lot of vibrations, else they will make a lot of strange problems, so be careful...

Also, when you are still "under the hood" I would suggest that you double-check the end of cd4/19's flat cable contact (which plugs in the player's PCB) and the connector on the PCB for wear - repairing them if needed. This will ensure an optimal contact, which is important since the transport (and it's undercarriage) vibrates quite a lot when playing. The vibration can loosen a contact, and cause a lot of strange problems with the player!

Also, please inspect (and replace if needed) the cable form the spindle motor to the PCB. Those wires are quite old and fragile, which isn't all that great if they are vibrating all the time.

Hope it helps,

Cheers!
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