Marantz M-CR603 SMPS Failure

[deckard]

Hi All,

I’m new here and this is my first post, although I am an avid viewer of the YouTube channel.

I have a Marantz M-CR603 amplifier that died on me. I turned it on at the mains one day, there was a spark and bang and it would no longer turn on.

As this was a relatively expensive amplifier and I hate creating e-waste from items that can be potentially repaired, I've decided to try and diagnose and fix the problem myself.

I am very much a novice when it comes to repairing anything this complicated, I have the basic tools and some very basic knowledge, but that’s it.

This is how far i have got:

• I have taken the unit apart and there is an obvious area of charring on the power supply module. From the service manual I understand this is a switched-mode power supply (SMPS), although I do not know how these work.
• The charring is on both sides of the PCB around an IC labelled “ICE 2B265”, there is a chunk missing from the IC and one of the pins looks badly burnt / melted. (see Picture01.jpg)
• According to the datasheet the IC is an “Off-Line SMPS Current Mode Controller with integrated 650V/800V CoolMOS” and I have ordered a replacement on the assumption it needs replacing.

What i am unsure about:

• On the reverse of the PCB there is a component labelled “JS93” that also looks badly burnt (see Picture02.jpg). There are other “JS” components on the board and they all have “0” on top. On the circuit diagram it is shown as two circles connected with an unbroken line (see Picture03.jpg), is this just a jumper component, a zero-ohm link?
• I have tested for continuity on this component and there is none, whereas there is on the other JS components, so I assume if it is a zero-ohm link I just need to find another that will fit the space?
• The trace leading to “JS93” also appears to be damaged / melted (Picture04.jpg). I've looked up methods for repairing this, but this isn’t something I've done before, is there a recommended method for beginners?

Given all of the above I am starting to doubt if the failure of “ICE 2B265” could have caused all the damage or if its failure is just a symptom of an issue somewhere else. The rest of the PCB looks fine, there were a few spider webs inside when I opened it up, not sure if they could’ve possibly caused a short that led to the failure.

Is there anything else I should be looking for before attempting to fix the issues I can see? I’m reluctant to poke at it with a multi-meter while it’s connected to the mains, but I'm willing to attempt the replacement of the components that are visually an issue.

Any help or guidance would be greatly appreciated.

Thanks

[FIXITNOW2003]

i would check the ESR of the electrolytic capacitors especially the main smoothing one

[Chris56000]

Possibly, but that's not the first thing to go for in dealing with a catastrophic failure like this!

What is far more important is that a regulation fault may have caused this, and as well as the smps IC itself, any of the following could also have been damaged :–

R910, D913, D914, D935, Q901, as well as jumper link JS 93 and the i.c. itself!

The OP needs to replace as a minimum :–

C906, C907, D913, D914, D935, IC92, PC92, PC93 (Opto–couplers for feedback and standby control), Q901, check and replace R910 if damaged, and make sure that the 330K resistors R981, R982 and R983 aren't high in value or open circuit, as these last three resistors can cause the i.c. to fail if one goes o/c!

Chris Williams

[strawberry]

C910 ?

[Chris56000]

C910 is part of the snubber protection network for IC92 so it's definitely worth a check – these high voltage ceramic or film type capacitors usually show obvious signs of failure when defective – if it looks OK it probably is, but obviously make sure it isn't simply dry jointed!

Chris Williams

[David_AVD]

I've seen SMPS IC and FET failures due to the main filter cap going low capacitance / very high ESR.

In those cases I would guess that the peaks that are no longer being filtered exceed the ratings of the active devices.

Something else to check after a primary side failure is the NTC in line with the active. I've seen them go high without any visible damage.

[deckard]

Many thanks for the feedback, and apologies i haven't looked at this in a while.

I have:

• Replaced the blown SMPS IC (ICE 2B265)
• Fixed the broken trace, with a bodge wire
• Replaced the blown fuse

The good news is it didn't blow up, the bad news is it still doesn't work. The caps are charging on the AC side, but nothing is getting through to the DC side.

I'm going to work through the suggestions here and see if i can find any more faults and i'll update if i have any luck.

Thanks again

[David_AVD]

Also check all the resistors on the primary side, especially the lower value ones.

When a switcher chip or FET goes bang, it often takes out the sense or gate drive resistor.

[fmashockie]

In the photos you shared, one of the joints to the zener diode D913 is in real bad shape (see attached).  Could be causing an open connection.  I would be checking the electrolytic caps, and any diodes (like UF4007 D905) in close promixity to the AC/DC converter that fried, as well as the zeners that make up the feedback circuit. 

[David_AVD]

Looking at the diagram, it's likely that R910 (0.68R 1W) will be open circuit after a blown chip.

[deckard]

Many thanks, I have had another look at this again today; the R910 (0.68R 1W) resistor was indeed open circuit and the zener diodes near the optocouplers and blown SMPS IC were short.

I wasn't sure how to properly test the optocouplers as didn't have the bits needed to put them into a circuit, but i put the diode side into my cheap TC1 multi-function tester and it tested okay, and the sensor side wasn't short, so i am assuming they are okay for now.

Every cap i have tested was reading okay and the resistors R981, R982 and R983 also tested okay.

• C906 - okay
• C907 - okay
• D913 - okay
• D914 - short
• D915 - okay
• D916 - short
• D935 - short
• IC92 - blown - replaced
• PC92 - seems okay, diode tested okay, not short
• PC93 - seems okay, diode tested okay, not short
• Q901 - okay
• R910 - open circuit - replced
• R981 - okay
• R982 - okay
• R983 - okay

I have replaced the R910 resistor, but will need to order the diodes, i will update once i have replaced them.

Many thanks again