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[danzigfan]

Few pics of it (I'm at work and forgot which model it is but I'm searching for it)  

[danzigfan]

Found it Marantz MX550

[SIR Philbutt]

This is definately a switch mode psu. There does not seem to be any visible problems so this is a good sign

Problem is that some have to be connected to actually work and be tested, If I recall correctly

Obvious things to check are the fuses next the transformer
Also the two transistors 7431 & 2. These are the ones that do the switching (with the chip 7352) and tend to be the ones that fail. Look up online the type and you should be able to find an uprated replacement. RS components or even Farnell.

Also 7351 & 2 may not be able to be tested by resistance. re-connect and see if they get hot. if so replace if you can find

Best of luck
Phil

 

[Marks DTM Calib]

Its a proper linear supply.

Measure those three round fuses and check they are ok.

I suspect connector 1345 has AC volts on it so check for AC here when its on (if you tried measuring for DC you would get weird readings).

The rest of the components look to be a HT power off circuit (7353 is an opto to support issolation for the switching) and hence for the rectifier diodes to support generation of a low current standby supply.

The disc in question is a ceramic cap and in conjunction with the common mode choke next to it (the toroid with the wires) its allowing the unit to meet emc emmisions by blocking the common mode noise.

[Marks DTM Calib]

This is definately a switch mode psu. There does not seem to be any visible problems so this is a good sign

Problem is that some have to be connected to actually work and be tested, If I recall correctly

Obvious things to check are the fuses next the transformer
Also the two transistors 7431 & 2. These are the ones that do the switching (with the chip 7352) and tend to be the ones that fail. Look up online the type and you should be able to find an uprated replacement. RS components or even Farnell.

Also 7351 & 2 may not be able to be tested by resistance. re-connect and see if they get hot. if so replace if you can find

Best of luck
Phil

 

Nah, not convinced it it 

[SIR Philbutt]

This is definately a switch mode psu. There does not seem to be any visible problems so this is a good sign

Problem is that some have to be connected to actually work and be tested, If I recall correctly

Obvious things to check are the fuses next the transformer
Also the two transistors 7431 & 2. These are the ones that do the switching (with the chip 7352) and tend to be the ones that fail. Look up online the type and you should be able to find an uprated replacement. RS components or even Farnell.

Also 7351 & 2 may not be able to be tested by resistance. re-connect and see if they get hot. if so replace if you can find

Best of luck
Phil

 

Nah, not convinced it it 

Not going to argue - been a long time since i did this type of stuff. will give in to more recent experience 

[Marks DTM Calib]

A few reasons

1) No secondary control section
2) Transformer has a LOT of iron in it (key reason you use a switch mode is to reduce the iron and hence the size and weight)
3) Marantz pretty much always have linear supplies which gives a better transient response for the audio
4) No large HT cap to create the required HT DC supply required switcher primary
5) No where near enough EMC filtering

 

[Kevin Wood]

A few reasons

1) No secondary control section
2) Transformer has a LOT of iron in it (key reason you use a switch mode is to reduce the iron and hence the size and weight)
3) Marantz pretty much always have linear supplies which gives a better transient response for the audio
4) No large HT cap to create the required HT DC supply required switcher primary
5) No where near enough EMC filtering

Yep, agreed. Although on first glance the amount of circuitry on the primary side suggests it might be a switcher, It's not.

[danzigfan]

My face at the moment is like this... After I get home and take a sleep I'll take another detailed read trough all posts and hopefully make some progress. Guys, thanks for help. I will keep you informed of progress

[SIR Philbutt]

A few reasons

1) No secondary control section
2) Transformer has a LOT of iron in it (key reason you use a switch mode is to reduce the iron and hence the size and weight)
3) Marantz pretty much always have linear supplies which gives a better transient response for the audio
4) No large HT cap to create the required HT DC supply required switcher primary
5) No where near enough EMC filtering

Yep, agreed. Although on first glance the amount of circuitry on the primary side suggests it might be a switcher, It's not.

Right ok guys have given up - your right  what does he do to fix it 

[zirk]

looks like a normal old fashion transformer to me, so if its got 240 volts going in to it (and thats confirmed) I would check if theres a link some where in the middle for the 110 v market, normally goes 110v, plus link, 110v, check for dry joints etc, failing that I would diss one side of the output of the transformer so as to isolate the the rectifiering cct and see what its pushing out AC wise, guessing 20v AC o/p would give around 24v+ DC once rectified and smoothed, if the AC o/p volts drop with the rectifier cct back in play the check the DC rectifier, smoothing Caps and Voltage stablisers etc.

Chris.