Marantz 6000 ose error

[davidsrsb]

My cd player started to get hard to start as soon as the warranty expired.
What happens is that when a disk is loaded, the disk is not detected and I see that is does not spin. After several loads and waiting the disk spins and reading the TOC gets ERROR
After a couple more tries it reads the TOC and I get another ERROR on play. Then it works for the whole CD without problems. Playing another CD quickly has no problem. If I wait a bit I get a couple of cycles of problems. The next day back to square one.
If the machine is left off for weeks, the "warm up" can be a few hours.
It has behaved like this for a couple of years.

I tried the 10pF capacitor next to the 74HCU04 mod, but no change.
Anybody know if this machine has a service mode?

My digital camera shows the laser is pulsing and I tried cleaning the lens.

[Fidelity Audio]

This may not be your problem but I have found the grease on the traverse deck to go hard (especially in smokey homes) and this softens has the player warms up. It stops the laser tracking.

Clean the grease off and see how you get on.

[davidsrsb]

There's no smokers around, but I will have a look.
I took it into my (air conditioned) lab and it worked fine. I have had a very good look under an inspection microscope for dry joints.

I am not too impressed with the master clock quality on the TC160, it looks jittery and this is an oversampling single bit player, which is supposed to be very sensitive to jitter.

[Fidelity Audio]

The marantz (like many other manufactures) have bad clocks.
They run just in spec for the standard 50ppm max.
Fortunatly the rest of the player is good so changing the clock for an after market one will bring big benefits to the audio.

[Extreme_Boky]

CD 6000 models have problems reading some disks. It is a known problem, so you should search the forums. There's a 10pF cap missing that causes grief. See attachment (and search the forums for more info...)

Cheers,
Extreme_Boky

[davidsrsb]

As I said, I have already made the 10pF mod.

I took the unit home, put it back together and immediately back to faulty behaviour. Thinking about it, the problem may be light level related. With the case open and in my well lit lab no problem. I could see 100 Hz signals on the servos caused by the room lighting. Stray light could easily reduce the laser output a little and modify the focus diode outputs.

I don't have a schematic for the VAM1201/2, only the CD12.x so what is the 74HCU04 doing?

I hope the mechanism is not failing as I don't know where to buy one here.

[Fidelity Audio]

The 74xx04 family of ic is a HEX INVERTER.

It is probably used as a linear amplifier.

Pin outs-

in - out
1 - 2
3 - 4
5 - 6
9 - 8
11 - 10
13 - 12

7 = gnd
14 = Vcc

Hope this helps

[davidsrsb]

I know the 74HCU04 pinout, thanks.
I now know that during the fault the diode amplifier outputs of the TDA1302 barely rise above 0V and even dip below.
Once working the outputs are around 3V. This is pointing at either the laser not firing properly or a missing Vdd on the 1302 or the servo amplifier chip. I measure 5V on the laser board, but it does drop down by 100s of mV when the laser is active.

It would be very handy to have a schematic for the cd tray assembly. I hate track tracing on flexible pcbs.

[davidsrsb]

Correction to my previous post, the pinout of the 1210 transport is very different to the CD12 and I was getting mixed up.
The diode inputs to the 1302 are around 1V, the outputs very near zero even when working, this must be a true current interface to the servo.

Does anybody know the "correct" laser current on one of these?

Assuming that the laser stabiliser is the same as the CD12, the circuit settles to the point where the voltage caused by the monitor diode current across the variable resistor is one Vbe. As my ambient is around 30C, Vbe will be 20mV lower than in a typical factory so the laser output will be slightly down.

[davidsrsb]

This looks like a similar problem to an earlier thread:

Cold start problems with CD transport

The laser is OK, I tried turning it DOWN and the drive still works fine when warmed up at home. I tried changing the 47uF capacitor between the TDA1302 and the 74HCU04 as it measured leaky, there is very little dc bias on it.

In my lab there is no warm up problem. I am thinking about the mains supply. There seems to be plenty of headroom on the 5V regulators, but in the lab I noticed that the 7918 has very little voltage across it. This seems to be sitting on top of a -12V giving -30V. Could this be for the flourescent display? I don't see why this dropping out would cause the cd to malfunction betond display flicker though.