Marantz CD5000/Philips CD753

[damiangt3]

Marantz CD5000/Philips CD753 overheat and reset

My first post here and hopefully one of many.

I'm modding a CD5000, so far I've replaced all the electrolytics in the PSU stage and the DAC stage (other than the existing Cerafines). The original 3300uf had literally had one of its legs blown off and some evidence of excessive heat around the 7805 (on the circuit board and case directly above the regulator). As a precaution I've replaced the 7805 and mounted a heat sink.

My problem, is as follows, I can play around 3 songs (10-12 mins) before I can 'smell' the excessive heat and feel it on the 7805 and then both channels start to distort before the player finally stops and I have to let it cool.

I'm struggling to work out what's going on here, does anyone have any pointers?

 

[Mooly]

78 series regulators can be troublesome in themselves... its not unknown... and so I would replace it as a first step. The 3300uF having failed suggest that something else might be going on. It would be advisable to check the voltages being applied to the regulator and across the 3300uF cap. Is it correct and not high ? Any chance the unit could be set to an incorrect mains voltage ?

 

[damiangt3]

78 series regulators can be troublesome in themselves... its not unknown... and so I would replace it as a first step. The 3300uF having failed suggest that something else might be going on. It would be advisable to check the voltages being applied to the regulator and across the 3300uF cap. Is it correct and not high ? Any chance the unit could be set to an incorrect mains voltage ?

Many thanks for the input.

A very odd situation! I ended up with a 'spare' Malaysian built CD5000 thanks to eBay so took my 'modded' AF board and swapped it and it worked, temperatures were fine, no overheating or rebooting.

Would a faulty VAM or display cause the excessive heat issues?

 

[Mooly]

Pleased to hear you have it working. It would have to be a pretty catastrophic failure to pull so much current because the VAM and display are all essentially pretty low current areas of the unit. If it were though, then as far as the display circuitry goes, something would be frying. The VAM, well I suppose its possible but the same applies, something would be getting hot on it.

 

[damiangt3]

Pleased to hear you have it working. It would have to be a pretty catastrophic failure to pull so much current because the VAM and display are all essentially pretty low current areas of the unit. If it were though, then as far as the display circuitry goes, something would be frying. The VAM, well I suppose its possible but the same applies, something would be getting hot on it.

I'll have to see what happens when I power the other unit up


Thanks again!