I can't count the number of times in the 80s and 90s when I worked on Japanese-made products when the glue on the board to hold down components would become conductive and just give me fits. It was very common in VCRs and TVs.

Problem with most switch mode supplies is that schematics for them are not available. If you would have found the switching transformer had an open primary, that would probably have been that?

Thank you so much...

Futaba does RC stuff dont they ??? controlers and servos . had few of there servos in rc cars and helis

Could we solve this by using component tester to show high leakeage? If we dont have curve tracer, can we use simple component tester and pay attention to leakeage current? Its Reverse Current, Ir? Or I am wrong?

It was the first video that I watched as well and then I was hooked : )

Same here. I'm an industrial electrician now. Thanks, Mr. Carlson. You'd be surprised how much these videos you make have given me joy. There was a time when i had none, and now I have a family and career i love. I'll watch every video you ever put out.

Same and this radio reminds of that.

Lol, I don't know about it being a treat, more like scary, cause I have one of these rigs. I need to make sure and put Mr.Carlsons vids in a playlist in case mine dies

Thanks for your kind comment, and feedback too!

Thank You for your kind comment, and feedback.

Glad you enjoyed David!

What I would have liked is to see another method to find this issue, since a multi-meter was unable to do it, but hardly anyone is going to have a curve tracer.

Loecurious,@@leocurious9919, An alternative would be to use a variable DC power supply and connect zener diode and your multimeter in series with the variable voltage source and look for leakage as you increase voltage. If you see a gradual increase in voltage before getting to the zener regulating voltage. You would then know the diode is leaky. Hope I explained it good enough for you.

@@leocurious9919 Realistically, a simple curve tracer can be built by anyone with an oscilloscope, old or new, plus a small transformer, one resistor and a set of probes. Mr Carlson's tracer is just a slightly more advanced take on the old "Octopus"-type tracer You sweep the x axis with a sine voltage, current limited (usually you do 1.5 to 5V to avoid damage to TTL circuits, and limit the current to maybe 1mA max due to a direct short) by a 1k resistor and read off the current with the resistor. A scope in XY mode provides the display, and since the resistor is 1k you read off mA directly on the scope, and volts across the X axis. Simple as that, less than ten components and you have pretty much the same curve tracer. Just search for "Octopus curve tracer" and check the images, you'll have a visual description of what I've just said. Diodes act the same way as on Carlson's video, resistors, capacitors and inductor all have their own "signature" curve. Combinations of them, too, are visibile and very informative!

I have a curve tracer oscilloscope kit, which I rarely use. This video reminded me to use it more often. I certainly would have probably thought that Zener was fine.

HO yes, feedback loop, big voltages, lots of power... I'm not an expert so what I usually do is find the loop, open it, and start from there by seeing what it does section by section with a dummy load. Of course, if the first thing it does is explode, you know you had RIFA caps somewhere...

My experience told me I would have never figured that out. I have no tool that would have let me diagnose a zener diode failure like that of even to check it past the multimeter. I probably would have just slapped a resistor in there and left it at that.

@@coll6 either substitution or a series resistor and power supply to see what it breaks over at would easily tell you. I usually went with substitution, as I kept a shelf full of parts in stock for repairs.

You're very welcome!

Howdy! That is real interesting, I must admit. Could you please help a fellow and share the link to one you've made? Thank you.

That used to be a beginners project, with a complete discussion of theory of operation, back in the day. If there's one thing I've never declined, it wasn't another drink, it was offered free training. :)

You bet!

You are very welcome!

Now that sounds logical…. Lol

I find his voice so shooting and relaxing that is actually therapeutical for me. My down trobleshootings are a lot more frustrating, usually!

SMPS can be designed as quiet as you want it to be, it doesn't have to be noisy. They're only ever noisy if they don't need to be quiet!

My Icom IC 736 has a built in switching supply. I bought it new in 1995 and it is still A-OK to this day. No noise, quiet as a mouse RF wise.

@@jagmarc True. And Yaesu employed a significant amount of shielding; in SMPS the transformer itself ends up being a 100 kHz or 200 kHz 'LF antenna'. I have a few LED ceiling lamps and 5 VDC USB power supplies which can wipe out the entire LW and MW band on every radio in the house with exception of a few 50 kW 'local' AM stations, and even they suffer noise. It is amazing Yaesu was able to shield the SMPS so well it can be located right _inside_ the radio with no trouble.

This particular SMPS is a *Forward* Converter, inherently quieter from the start. Plus it includes some neat architectural features to make it quieter (someone else can mention them). It's the *Flyback* Converter type SMPS which gives all the bad name to switchmode supplies and it's because they're so cheap to make, mainly a flyback transformer is trying to do two jobs in one. Instead of it having an outboard inductor to store energy (i.e. L3 on this psu), with a Flyback C. the energy to 'flied-back' is packed inside a teeny weeny little gap put in the magnetic flux path, a gap in the core. Then with a sharp bang the energy flies over to the secondary, and zapps through leakage inductance, like a genie escaping a bottle, no wonder it's so noisy. These Forward Converters are a completely different animal. They don't store energy in a gap in the magnetic core, in fact it's the opposite there needs to be an active clamp to *reset the core* every cycle, if not it'll 'pump-up' and then saturate, ... bang.

Thank you kindly!

My pleasure

Good on you Dennis. Go for that repair. I adore my 990s. Dont hear them so much now. But when you you do.......... The reports I have had. 73 de Mike.

No problem 👍

Hey, it is Mr. Carlson :)

Many thanks!

I appreciate that!

My pleasure!

You're very welcome!