Marantz cd94 mk1 power supply problem

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I’ve just picked up a tatty cd94 mk1 that i am hoping to tweak over the coming months. (I can’t bring myself to modify the other ones that i have as they are in such good condition).

When a cd is inserted, the lens attempts to focus but the spindle does not start. The display then shows ERROR. I have replaced the notorious 33uf caps on the cdm, thinking that this might be the problem but this has not helped. I then proceeded to check all of the power supply rails. These all check out except for the neg 6 volt feed, which measures +0.755 volts. This appears to control the laser on/off from what i can see in the manual, so i assume that this is the problem.

I traced the rail back from the point of measurement (connector J802 on the lower LHS of the power/dac board) to the components that i assumed were at fault - D821, 6.8v zener; Q821, 2SA1358; C821, 220uf cap; and Q822, a 2SA1175. Interestingly Q822 is shown in the service manual as being a fuse, and not a transistor. All solder joints were old so i am sure that the parts were all original. Nevertheless, I have replaced these parts but the problem is still there.

I have also checked for dry or cracked solder joints on the power/dac board but can find none.

The player has an early non-A dac and i have been unable to find a circuit diagram that exactly matches. As i said above, there seem to be a few differences between the only circuit diagram i can find online and this machine. My other 1541A mk1 is slightly different to this one.

Can anybody offer any advice?
I have a MKII circuit diagram, but I could identify the components you mentioned. The -6V is derived from the -12V from Q831.
There are only a couple of components, but first I would check if there is no excessive load on the -6V. Cut the trace after C821 and check.
Check also -5V going to R824, and the voltage on D821 Zener diode (7.5V).
Hi Simtu,

The Philips CD960 is basically the same player as the Marantz CD94 mk1.

The CD960 service manual (in Dutch) is available from The HiFi Engine.

I own an early CD960 (now sympathetically modified) and I can take measurements from it for you if you need any.

Regards, Mike
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