Repair Marantz M-CR603 - asking for help

[Nikske]

Hi all, I am not a specialist at all but I am interested in repairing stuff, I can read schema's, I know to measure some things, and I have a Marantz M-CR603 CD receiver which is completely dead.

I have the service manual, opened the Marantz and discovered quickly there was a problem on the power board (SMPS), as expected.

On the connector to the main board, there was no power on all of the pins.

So I measured at both sides of the three transformers TF91, 92 and 93. I had 318V at the high voltage side, 0V at the low voltage side. So the problem is somewhere at the high voltage side.

Examing the board, I saw no distroyed components like capacitors, ... , the fuse is OK. I measured the big capacitor, is OK. I checked all the diodes I could measure, they seam ok.
There was a slightly darker zone on the board, maybe D908, C917 or R928 where bad. But I measured R928, seems ok. C917 is a ceramic capaitor, compared with the other one (both 0,01µF), seems like they are both ok (not really sure, capacitor tester showed not really 0,01µF but for both the same value - not sure of ceramic capacitors can be measured with my tool).

When I looked at the power diagram, I thought it could be one of the IC's, but that's not right because I get power on the high voltage side.

Can anybody help me a little bit please?

[jonpaul]

Bonjour, troubleshooting  of off line SMPS can be complicated, as the most likely cause is a blow power transistor, FET or diode, with cascade of fail to other connected components  like drivers.

The fail; is seldom a transformer or just one part.
Do you have service manual? If yes it may have a flowchart for SMPS dead.


finally Beware that SMPS  has  360V , stored energy,   hazardous to your equipment and to you.

 SMPS folk will use a mains 1:1 isolation transformer, and perhaps a variable autotransformer (Variac)

Bon chance

Jon

[Nikske]

Merci bien jonpaul!

I am aware of the high voltage and the stored energy (measured the capacitor already, stores high voltages during many minutes).
In the service manual nothing is mentioned about the SMPS....

So a new SMPS will be the solution?
Still, I want to learn, but because of the high risk maybe not interesting....

[jonpaul]

Rebonjour cher Monsieur, bon pour  un  Belgique, BRAVO pour votre efforts!  j'ai fort connexion U. Kathloc   Louvain , et Sylvania, a  Tijenins,

1/  old Marantz were made in China and generally have little value or service info.  We knew the 1960s original USA Marantz valve classics, and Sol Marantz sold his business, name and trademark to Sony Superscope in 1972 for $100K.

2/ Replacing the SMPS will be a project as the output voltages, secs and size need to be duplicated.

3/ Your excellent photos of the SMD PCB show possible damage/corrosion/burn but will not aid diagnostics much.

4/ I would start at the switch transistors, remove the test the transistors out of ckt.

Likely you will see one or more blown open or short. The trace back to the drivers.

5/ Softstart, startup sequence, and feedback loops will need to be studied and understood.

See the many fine texts and sites on SMPS design and theory of operation.

6/ EEVblog has many threads and posts re isolation transformers and diff probes for lab use.

Grounding and safety is an issue as 360V bus can be lethal.

Many scopes cannot probe >300V safely even with X10 probes.

Bon chance avec  les traveaux....

BON NOUVELLEE AN 2024

Jon

[fzabkar]

Is there a supply voltage at pins 4 and 5 of IC91 (bottom left corner of diagram)? If not, then one of the 330K startup resistors (R981, R982, R983) may be open.

Also check C902 (Vcc pin #7). These capacitors often go high ESR, resulting in "hiccuping".

[Nikske]

Is there a supply voltage at pins 4 and 5 of IC91 (bottom left corner of diagram)? If not, then one of the 330K startup resistors (R981, R982, R983) may be open.

Also check C902 (Vcc pin #7). These capacitors often go high ESR, resulting in "hiccuping".

I get voltage on pins 4 or 5. I don't know if it's the right voltage, but there is. (> 100V).

But...... thanks for the tip -> C902 desoldered, and there is no capacitance. I also checked the other two in the neighbourhood on the print (C906 and C907, allthough they are in the IC92 part), they where correct.

I looked in my personal stock and only have 50V 22µF zo I will order one (original is 100V). I'll keep you updated!

[fmashockie]

You're off to a good start! C902 is part of the feedback circuitry for IC91 (ICE3B0365) which is an AC/DC converter.  You cut off the remainder of the schematic but if you follow that trace, it should run to some optocouplers which get feedback on the secondary side.  If that path is interrupted (for example by C902 going bad), you power supply will 'hiccup' or go into an auto-restart mode. Also, C902 is charged by the Startup cell of the IC to above the IC's turn-on threshold voltage of 15V.  Once that 15V is reached, the IC's internal circuitry begins working.  So again, if that voltage can't be reached due to C902 being bad, the IC goes into auto restart mode.

You can tell a lot about these ICs by checking the waveforms of specific pins on them.  It can tell you a lot about the state of the IC (normal operation, active burst mode, autorestart, etc).  And these waveforms are available in the datasheets for these ICs if you look up their part #s.  Also, here's a link to an application document on these CoolSET F2/F3 AC/DC converters that provides more waveform examples and details on how they work.  Just be careful like Jon says about probing these ICs due to the high bus voltage nearby.

https://www.infineon.com/dgdl/Infineon-Design_guide_integrated_power_stage_CoolSET_F3_ICE3Axxx-ICE3Bxxx-AN-v01_01-EN.pdf?fileId=db3a304412b407950112b418ff04272e

[Nikske]

Thanks for the interesting explanation! When I will look at the info of the IC's.

I looked for some info of that particular capacitor too, and it is designed for about 2000 hrs of operation. Time to get a replacement capacitor with more decent hours to go. And that means the other capacitors "can" die soon, too (or are almost dead, but now I'm not going to desolder them all to check the ESR values).

[Haenk]

Thanks for the interesting explanation! When I will look at the info of the IC's.

I looked for some info of that particular capacitor too, and it is designed for about 2000 hrs of operation. Time to get a replacement capacitor with more decent hours to go. And that means the other capacitors "can" die soon, too (or are almost dead, but now I'm not going to desolder them all to check the ESR values).

The lifetime is always given at maximum operating temperature (plus some other electrical parameters); if you are not running at that temperature, the expected lifetime will go *way* up. But it's always a good idea, to use a major brand capacitor with a good temperature rating. 105oC is a good choice.

[floobydust]

[...] old Marantz were made in China and generally have little value or service info.  We knew the 1960s original USA Marantz valve classics, and Sol Marantz sold his business, name and trademark to Sony Superscope in 1972 for $100K.

What is "old"? I have late 1970's-80's Marantz- all made in Japan.

[fzabkar]

I remember when Marantz was an upmarket Philips brand.

[Nikske]

@fmashockie: SUCCESS!

Thanks @everyone for helping.
C902 was indeed the guilty one.
Changed it today and hooray!

(and I learned some extra "circuit board understanding", thanks!)

see the 3 images below...

[fmashockie]

Awesome! But fzabkar called it first!  Glad you got it back up and running again! 

[Nikske]

indeed, thanks to fzabkar and jonpaul too!