voltage spike ?

[kk4fpx]

I traded for a Yaesu FT-450AT that didn't work. The guy I got if from said he was quoted $150.00 to fix it from the factoty. Actual charges came to $300.00. Anywho They ( the factory tech ) said it had most likely received a high voltage spike. The guy I got it from thinks it was because he had it hooked to a switching power supply ! Now I'm afraid to hook it to my SEC1235M switching power supply. but it's the only supply I have with enough amps.
Any Ideas ?



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[NQ6U]

Don't sweat it. Almost all the 13.8 VDC power supplies out there are switching power supplies. I've been using one for years without any problems.

I'm guessing that the guy who sold you the radio either had a really bad power supply or—more likely—he's not telling you the complete truth. He probably did something dumb and is embarrassed to admit it.

[N2CHX]

Almost every power supply in every computing device today is a switching power supply. All a "switching" supply is, really, is a high frequency (within the audio range, usually) oscillator, which drives high-current transistors in a switching (on-off) mode and a feedback loop which changes the duty cycle for voltage regulation. The output is smoothed/filtered by capacitors and sometimes inductors, and the filtering is much easier to accomplish than with a traditional power supply because of the higher frequency requires much less capacitance to remove the ripple. The biggest problem with switching type supplies for radio communication devices is the fact that amplifiying square waves creates a lot of harmonics and noise (from internal intermodulation byproducts); but that noise is easily filtered out if the supply is well-shielded and the output well-filtered.

In summary, I think the guy you bought it from doesn't really understand what a switching supply does and how it works. I'd bet my money on him connecting the radio to the supply backwards being the culprit here. ANY power supply can fail in a manner which would create an overvoltage situation at the output. There is usually a crowbar circuit at the output to prevent slower overvoltage "spikes" and MOV's to kill smaller, faster ones.

In summary; I wouldn't worry about using a switching supply. Your biggest issue is likely to be noise in the receiver, but if that happens you can add your own filtering to quell it.

[N2CHX]

Don't sweat it. Almost all the 13.8 VDC power supplies out there are switching power supplies. I've been using one for years without any problems.

I'm guessing that the guy who sold you the radio either had a really bad power supply or—more likely—he's not telling you the complete truth. He probably did something dumb and is embarrassed to admit it.

Well damn, you beat me to it lol. I was typing as you were posting.

[NQ6U]

Well damn, you beat me to it lol. I was typing as you were posting.

Yeah, but you went far deeper into the topic than I did. Good info there.

[K0RGR]

There could have been a voltage spike down the power line, too. They take out switching supplies just as well as linear supplies. Usually when a switcher fails, though, it results in less output voltage or none at all - they don't usually fail in a way that would produce too much voltage. Linear supplies on the other hand can and do fail in a mode where they put out too much voltage. Most good linear supplies have crowbar circuits that effectively short the output in the event the voltage is too high. Unfortunately, sometimes the crowbar circuit doesn't work, doesn't work fast enough to prevent damage to this jewelry we call electronics.

[n2ize]

Not to mention that MOV's also go bad. They might protect you from a spike the first time round but may do nothing the next time.

[K7SGJ]

Just to be on the safe side, you may want to hook a 16v 1A ( or choose a value for the voltage you don't want to exceed) zener diode across the output of the supply if it doesn't already have one. Give yourself a little head room in choosing the value, as most radios will tolerate around 16 volts, but your needs may vary. If your output voltage ever goes above the value of the zener, it will turn on and blow the fuse on the PS, and maybe the zener, too. Very cheap insurance. I have one on all my supplies that don't have one. Even the ones that have over voltage protection circuits. It's a great last line of defense that may save a radio in the event of a PS catastrophic failure.

[kk4fpx]

Thanks for all the good info. I'll feel a little more comfortable using it now. I kind of think I did get some bad info from the original seller also. I think I'm going to really like this radio once I get used to it.. Can't find user manual for it FT-450 and FT-450D and they are 100 pages long.

[K7SGJ]

Thanks for all the good info. I'll feel a little more comfortable using it now. I kind of think I did get some bad info from the original seller also. I think I'm going to really like this radio once I get used to it.. Can't find user manual for it FT-450 and FT-450D and they are 100 pages long.

Try the Yaesu website, and download the manual for the FT450. I think the ATU (which is an accessory for the FT450 which would then make it a 450AT) installation and operation information should be towards the end of the manual. The 450AT is the same radio, only the ATU was factory installed. All the available accessory install/operation information should be covered towards the end of the manual, unless you happen to find an individual file that covers a specific accessory, which is rare. That's the way Yaesu use to do it, I doubt they have changed. But then, I could be full of shit, too.

[NQ6U]

But then, I could be full of shit, too.

Could be??