SMPS from Marantz UD-5007 defective

[Vintagelover]

Hello guys,

I'm new to this forum but as many of you I'm very interested in the technical side of electronics, especially about audio equipment.
To enhance my knowledge I started to recover defective audio products and try to repair them.

I have a Marantz UD-5007 bluray/CD player that doesn't turn on.

When measuring the voltages I noticed the 5V standy voltage isn't there.
In fact it's only 3.7V. I replaced the ZD502 with a new specimen but that didn't help.
I also replaced all electrolytic capacitors, there no solution either.

Now I'm starting to wonder if the regulating IC U503 does work properly.
The resistor R552 measures just fine, R554 is difficult to measure. My multimeter swings from 6k to 10k, even if I measure exactly at the resistorlegs.
Could this be because one of the capacitors is throwing off my measurement?

Also the optocouplers are hard to measure because they both have resistors parallel over them.

So, in short terms, I don't know what to do next. My plan was to replace U503 but since I have 3.7V it seems to work, only not in the right voltage...

Thank you in advance

[Phil1977]

Hi and welcome!

Can you please post a picture of the power supply board and note where you have measured?

There are a lots of geeks out here, but chances of someone having the internals of this vintage device completely in memory are small.

[wasedadoc]

A tip for anyone seeking help with a repair. If you have already found a link to a free online copy of the service manual or schematic please include it in your post. Saves everyone else having to search.

[Vintagelover]

Thanks for the reply.

You're right, a schematic is very needed

This is the service manual:

[Vintagelover]

 Anybody a thought? It’s much appreciated

[squadchannel]

have you checked to see if there are any other voltage rail issues? just 5V?

The U502 optocoupler is another suspect. performance may be degraded.

[Vintagelover]

There is also no voltage on some of the zenerdiodes like ZD505 and 506 if I remember correctly. I can measure it again tonight. In the attachment there is only a part of the service manual as the file (10 Mb) is too big.

On other pages there is stated that the 12V is enabled when you activate the unit via the 5V line. So the last one should always be available.

So an optocoupler can be worn? It would explain why I have a voltage but not enough.
Does the diodetest work even when there is a resistor parallel? Or will it affect my readings?

[wasedadoc]

In the attachment there is only a part of the service manual as the file (10 Mb) is too big.

Can you post a link to the complete service manual?

[Vintagelover]

Here is the complete service manual, I compressed it.

[FIXITNOW2003]

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