Sony HCD-MJ1 receiver died on me while on standby

[Les Jones]

No, you need something that will pass the likely normal operating current without a significant voltage drop. If the fault is still present a higher current makes it easier to see very small voltage drops (In the milivolt range.) across sections of sections of the track. This helps to isolate the faulty component without having to cut tracks or remove components. (This method only works if there are sections of track that enough resistance to give a measurable voltage drop.)
Edit. You are correct these two fuses blow if anything drawing power from the 10 volt winding on the transformer draws too much current. I would suspect the the bridge, the two voltage regulators fed from the bridge output, the capacitors on the input and output of these regulators and possibly anything fed via R716 (0.33 ohms).

Les.

 

[Nigel Goodwin]

No, you need something that will pass the likely normal operating current without a significant voltage drop. If the fault is still present a higher current makes it easier to see very small voltage drops (In the milivolt range.) across sections of sections of the track. This helps to isolate the faulty component without having to cut tracks or remove components. (This method only works if there are sections of track that enough resistance to give a measurable voltage drop.)
Edit. You are correct these two fuses blow if anything drawing power from the 10 volt winding on the transformer draws too much current. I would suspect the the bridge, the two voltage regulators fed from the bridge output, the capacitors on the input and output of these regulators and possibly anything fed via R716 (0.33 ohms).

Les.

Circuit protectors commonly fail for no reason at all - with the OP's lack of electronics knowledge his easiest solution is simply to replace the circuit protector and then see what happens, most likely it will cure the situation. If not, it will simply blow again - and we can discuss it further if that happens.

Assuming it blows again?, most likely cause would be the bridge rectifier (D821) - the voltage regulators and capacitors etc. are very low probability.

 

[Jean-Pierre]

That's music in my untrained ears. Il report back.

 

[Jean-Pierre]

This is from the part list in the service manual
< IC LINK >
ICP821 1-532-845-21 LINC, IC (4A 250V)(AEP,UK,G,IT,SP,HK)
ICP822 1-532-845-21 LINC, IC (4A 250V)(AEP,UK,G,IT,SP,HK)

Why are these in the US/CND 125 V world called fuses ?
< FUSE>
F821 1-532-782-11 FUSE, MICHRO (4A 125V)(US,CND)
F822 1-532-782-11 FUSE, MICHRO (4A 125V)(US,CND)

 

[rjenkinsgb]

They are fuses that should only ever fail if there is some component failure that could cause more harm or start a fire etc.

They (or similar things) are quite common, but most people never need to know about them, unless they repair things.
A bit like the thermal fuses sometimes built in to transformers or motors, inside the insulation.

Have a look through the 4A ones on here, with axial leads and rated 125V AC or above; Slow blow / time delay types are appropriate for feeding a rectifier and capacitor setup.

https://www.mouser.com/Circuit-Protection/Fuses/Fuses-with-Leads-Through-Hole/_/N-ba8hh?P=1z0x87jZ1yzshenZ1yzshdiZ1z0z819

Some may be too long, so check the dimensions.
You can see some are literally just conventional fuses with leads attached to the end caps.

The difference between Europe and USA is likely down to differences in equipment regulations.

Find the cause of the failure before fitting the solder-in fuses, though.

 

[Nigel Goodwin]

Find the cause of the failure before fitting the solder-in fuses, though.

As I mentioned above, they commonly fail for no reason - so with his lack of electronics knowledge it would be MUCH easier just to replace it and see if it blows again.

Even as a long time professional engineer that's what I (and any experienced engineer) would do - and that picture above shows it's REALLY simple to do, that style of circuit protector means you can just tack in on the top of the faulty one to test it. Or, looking at that image, even use miniature croc clip leads to connect one across it. Obviously it helps if you have them in stock - but if you're ordering one, order 2 or 3 instead

We also didn't stock that exact style (we kept three different types though), and would have replaced those with a plastic 'BC557' shaped circuit protector.

 

[Jean-Pierre]

The old fashion way. To the shop on my bike.

 

[Nigel Goodwin]

The old fashion way. To the shop on my bike.
View attachment 131508

Wow - I'm mega impressed you were able to find a local shop that sells them!

Such a nice blue as well.

 

[Jean-Pierre]

It works !! The Sony is back and I just had Christmas, new year and birthday at the same time. And yes I tacked it on the old one as Nigel proposed.

 

[Nigel Goodwin]

It works !! The Sony is back and I just had Christmas, new year and birthday at the same time. And yes I tacked it on the old one as Nigel proposed.

That was only a temporary suggestion, to see if it blew again or not - but if it's too hard to change, then leave it like that.

 

[Jean-Pierre]

Well I’ll leave it like that, it tells the story. How Nigel took an electronics toddler by the hand and guided me through the wood. Honestly I learned a lot this time. Thanks to your knowledge and patience. Here in Belgium we say : let’s have a beer together. Do I go to my fridge and you go to yours. Cheers.
But I thank also Les and RJenkins who were the first to save me from drowning. From the AC-board to the transfo, to the 14 pins on the main board and finally the blown soldered fuse. I won’t forget the trip in Covid time.

 

[Nigel Goodwin]

Well I’ll leave it like that, it tells the story. How Nigel took an electronics toddler by the hand and guided me through the wood. Honestly I learned a lot this time. Thanks to your knowledge and patience. Here in Belgium we say : let’s have a beer together. Do I go to my fridge and you go to yours. Cheers.

Actually, I have some beer in the fridge - but unfortunately my wife bought it, and wasn't wearing her glasses, and bought alcohol free beer instead!

I've got red wine though.

I've not been to Belgium, but my daughter lives in The Netherlands and has been many times - however, she lives near the German border now, so goes to Germany more than Belgium (cheap beer, and close). All her pictures from Belgium seem to be sat at a table outside a cafe, with a beer in hand - sounds a good place to live!.

 

[Jean-Pierre]

Nigel I hope you enjoyed the red wine ....
Instead of a beer I continued reassembling the Sony. All fine, but the mini-disc auto-loader was not working, there was a disc inside which didn’t want to eject. Damned. I opened the thing again until I could manually turn the mechanism until the disc was free. Done this before, because the initial repair last year was replacing the rubber belt. I close the Sony again again ..... no sign of life ! Opened again, I measured the fuses and found resistance on both. Still the joy of seeing it work was worth all the trouble. Of course I have no use for the Sony cd/md player recorder receiver, as I am hearing impaired and listen to the television with direct streaming. Now it is back on the shelf until I get the urge to tackle it again. And I know who to call....

I am sure you’re daughter enjoys living in Holland. lt is such a well-organized place, very strong economy. Belgium is cut in two because of the different languages. I live in Flandres and our language we call flemish, but actually is like dutch with an accent. Something like English and Scottish.
We have a big garden and for many years we criss crossed Britain, to visit garden en nurseries and went home with the car full of plants. Travelling to the UK was like leaving Europe then, and now it is again..... History repeats itself.
We’ll be back.

 

[Jean-Pierre]

NIgel, the Sony is still safe on the shelf.
What if .... I go for some new blue fuses and replace both this time ?
What if .... the blocked minidisc mechanism made the fuses blow ??
But now it not blocked anymore .....
Just a thought.

 

[Nigel Goodwin]

NIgel, the Sony is still safe on the shelf.
What if .... I go for some new blue fuses and replace both this time ?
What if .... the blocked minidisc mechanism made the fuses blow ??
But now it not blocked anymore .....
Just a thought.

Assuming the mini-disc is fed via those fuses it's certainly possible that the mechanism been jammed could have overloaded the fuses, and would explain the original failure.