Check power supply first. It's where most problems are.
Air-Force Schooling 101.

Edit: How do you check the power supply in a switch mode power supply?

Edit2: attached file

 

This is a great thread and it is nice to see so many sharing their experience. It is too bad there are not sticky threadsor something on doing things exactly like this. How many inquisitive minds follow this forum and have to piece together some way of repairing their own equipment. You guys have sort of laid out the foundation for going at a radio problem. But how do you inject a signal, where do you make these test points, how do you put a scope on this equipment and what are you looking for? A lot of hobbyists don't have time to go to school but they are doimg this on their own and risking their lives to do I because they dont know better. I know the first AM/FM stereo I did, it was a large learning curve and a lot of help from forums but I got it done and still here to tell about it. Thank you guys for all that you do on this forum. CHEERS!

That is an idea that I would love to see too. I am currently writing some of my experiences on smp fault finding. I only get odd moments (baby sitting duties permitting) to compile it so it gets randomly inserted and I wonder how many readers start at the beginning or just see the odd one or two. Maybe we need a "Thread series" heading.

 

Check power supply first. It's where most problems are.
Air-Force Schooling 101.

Edit: How do you check the power supply in a switch mode power supply?

Edit2: attached file

Have a look at my currently running thread "Switch mode Power supplies, My experience" If you have your own experience repairing them, please feel free to add any comments. I did post the On semiconductor link on there a while back, (post #19) Excellent info for those trying to get to grips with them

 

My first job was repairing oscilloscopes. One of the hardest faults to get started on was no display even with the beam finder - the fault could be almost anywhere and there is no obvious way to track it down. I came up with this to narrow it down:
Select channel 1, XY mode, turn up the brightness.
1. Check low voltage power supply.
2. Check high voltage supply (cathode supply)
3. Connect voltmeter between Y-plates and adjust Y-shift to get zero volts. Investigate Y amplifier if you can't get zero.
4. As 3 except for X-plates.
5. Short grid and cathode of the tube. If this produces a trace investigate Z circuit.
Now you are left with the tube or the anode supply.

 

I did post the On semiconductor link on there a while back, (post #19)

that's where I got it I thought it was good enough to put in again, Thanks for the link.

 

that's where I got it I thought it was good enough to put in again, Thanks for the link.

You may also like this one:-
There is not much else that isn't covered in here, and it contains many device specifications and other useful info.
Note to moderators, is there a way to link two threads as the two I'm running currently are now overlapping? Otherwise I will Have to post the same info on both threads.

 

To the other readers following this, I apologise for the diversion, but N11778 raised a point that needs to be covered, perhaps in more detail on my thread "Switch mode power supplies, My experience" to which I have a lot more to divulge as time permits. In the meantime, I will continue on My approach that was used in my business to repairing the radio asap.