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Old 22nd December 2005, 02:33 PM   #11
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Looking at the cd63 circuit (which will be similar) The 7918 outputs -24.4 volts and -31.5 on the input in stop mode . It has a 6.8V zener diode on its gnd to raise the volts. So if your input is the same as mine and it has a 12v zener on the gnd pin then there will be little voltage across it.

The output is labeled VFTD.

VFTD is the supply voltage to two transistors , one has its collector connected to the tube heater rails via 47 ohm resistors.
The other transistor controls the base of it. This one is connected the the 5 V rail.

You may have a dry joint on a smoothing cap on one of the voltage rails around a reg.
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Old 23rd December 2005, 02:26 AM   #12
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The layout of the CD63 is very different.
I cab see a 6V2 and a 4V7 zener near the 7918, so one or both of these could be used to lift the voltage for the FTD.
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Old 28th December 2005, 11:17 AM   #13
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Still working in the lab and severe warm up problems at home. I tried running from a Variac to see if it was fussy about the mains voltage but it works over a ridiculous range.

The diode outputs from the TDA1302 diode current amplifier to the servo chip look odd. During the disk check these pulse negative to -0.3V for 40mS. As there is only +5V power in the area this is hard to understand. I checked that the TDA1302 ground was actually at a clean 0V.

The decoupling in this player is awful, the lack of plated through holes means that chip decoupling caps have tracks several cm long to the nearest topside ground connection.
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Old 28th December 2005, 01:06 PM   #14
Arjanvm is offline Arjanvm  Netherlands
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Default here's service manual 6000

In case you need the service manual for the Marantz 6000 (maybe you already have it), have a look at my web server:

http://www.g-square.nl/manuals/maran..._CD6000OSE.pdf

good luck,

Arjan
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Old 28th December 2005, 04:00 PM   #15
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Thanks, I now find that once running, this machine is happy to play CDR, but does not play a very dark CDRW

There are 10k resistors on the servo inputs, it might be possible to see which way the current is flowing to get the -0.3V step.
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Old 29th December 2005, 08:26 AM   #16
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Quote:
In case you need the service manual for the Marantz 6000 (maybe you already have it), have a look at my web server:
Thanks Arjanvm !!!!!!!!!!


Quote:
Thanks, I now find that once running, this machine is happy to play CDR, but does not play a very dark CDRW
Your CD player (as all others that play CDRW) has detection mechanism (some sort of over-scanning) to detect CDRW disks. They have very low reflectivity, which needs gain compensation. Check if you have +5V on pin 11 - IC 7500 when you try to play CDRW disks. Same IC, pin 9 should have eye pattern signal of approx 1.5 V pp around 2.5V DC. Measure the amplitude of this signal when playing standard CD's. Now insert CDRW disk and measure the amplitude. It should be the same or within max (+ or – 0.3V), if gain correction works properly.

It is possible that laser diode is not receiving a full 4.5V in play mode. Replace resistor 3500 with 100K trim pot and adjust this voltage to exactly 4.5V (you can go a bit higher at the expense of laser diode “longevity”).

It is also possible that it IS receiving 4.5V, but the light output is low (aged - not likely, though).

It appears that IC 7404 is used to invert (and possibly amplify) HF signal to suit IC 7405 servo + decoder chip. The 10pF cap (2509) is there to prevent very high frequency rubbish to reach IC 7405. You can experiment with larger values (12pF).

Extreme_Boky
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Old 29th December 2005, 01:32 PM   #17
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IC7404 is a 74HCU04 and is being used as an inverting rf amplifier. This is a common way of getting a low performance wideband amplifier at a low cost. Video opamps only became cheap when adsl took off a few years ago.
This machine has had light use and the warm up problems started years ago, so the laser is probably ok.

The feedback loop on the flexible pcb using the monitor diode should make the laser reasonably independent of the supply voltage.
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Old 30th December 2005, 08:00 AM   #18
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I found that the diode inputs to the servo chip swinging negative is due to the chip itself, by disconnecting the ribbon cable. There must be an unusual ADC circuit.

The high gain switching is working, but the startup does not get that far as the disc does not spin and there is no RF output. The diode inputs to the TDA1302 show signal, but two of the centre diodes do not get near 1V. Time to start experimenting with the laser setting, what should the current be?
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Old 30th December 2005, 11:26 AM   #19
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Default Fixed

The High Gain line was always high and RF was about 0.5V pk-pk with a pressed cd.
Increasing the laser dirve to about 100mA and now it switches High Gain according to disc type and will play the dark CDRW

Another weak laser then, though I suspect this one was bad from new, this player never worked well with CDRW
I wonder how much a new VAM1210 tray or laser assembly costs?
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