Hello,
Since my marantz M-CR603 will not power on, I've decided to repair it.
From the main Switch Mode Power Supply board, no voltage is going out. Especially, a +6V is constantly supposed to go to the CPU for powering on by a push button.
I've investigated the transformer responsible for the +6V. If I understand well, TF91 receives at pin 4 the supply, and IC 91 switch it to have the transformer do his job.
Now I have two questions :
. Where is the Vcc voltage supposed to come from ? I see nowhere for it to go to the chip. Is the chip kind of self powered through the Drain input ? (I have the feeling to go crazy)
. When I measure Vcc, I find 9.2V. The datasheet says that working voltage is 10.3V, with on threshold at 18V. So maybe the chip is just off. A measure at the Drain input shows a stable 320V, the same voltage as the input of the chip, so no switching as it would do if on I guess
But still : where is this 9.2V coming from ? Not from TF91 since I measure 0V behind D901 ...
Thanks all !
EDIT : After attentive reading of the documentation of the switching chip, I think I've found the thing.
Actually, the switching chip is itself charging the capacitor at the beginning in order to activate himself. Once activated, the switching occurs, and then the transformer begin to create a voltage at its secondary winding on the primary side. Thus, the chip stays on. Finally, the Zener diode is there to prevent the voltage to go higher than 20V and protect the chip from over voltage.
Thus, I've measured the capacitor C902 who is supposed to charge up to launch everything : it's broke !
I am simply going to replace it. Hope this could be useful to someone else !
Since my marantz M-CR603 will not power on, I've decided to repair it.
From the main Switch Mode Power Supply board, no voltage is going out. Especially, a +6V is constantly supposed to go to the CPU for powering on by a push button.
I've investigated the transformer responsible for the +6V. If I understand well, TF91 receives at pin 4 the supply, and IC 91 switch it to have the transformer do his job.
Now I have two questions :
. Where is the Vcc voltage supposed to come from ? I see nowhere for it to go to the chip. Is the chip kind of self powered through the Drain input ? (I have the feeling to go crazy)
. When I measure Vcc, I find 9.2V. The datasheet says that working voltage is 10.3V, with on threshold at 18V. So maybe the chip is just off. A measure at the Drain input shows a stable 320V, the same voltage as the input of the chip, so no switching as it would do if on I guess
But still : where is this 9.2V coming from ? Not from TF91 since I measure 0V behind D901 ...
Thanks all !
EDIT : After attentive reading of the documentation of the switching chip, I think I've found the thing.
Actually, the switching chip is itself charging the capacitor at the beginning in order to activate himself. Once activated, the switching occurs, and then the transformer begin to create a voltage at its secondary winding on the primary side. Thus, the chip stays on. Finally, the Zener diode is there to prevent the voltage to go higher than 20V and protect the chip from over voltage.
Thus, I've measured the capacitor C902 who is supposed to charge up to launch everything : it's broke !
I am simply going to replace it. Hope this could be useful to someone else !
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