Technical Topics > The RF Workbench

ICOM AD-55 power supply output voltage adjustment

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alpard:
No, haven't done it yet.  I wouldn't imagine the output voltage from the AD-55 would drop a lot under the load. Would you?

Stretchyman:
A schematic would be useful!

However if it's a simple pass transistor linear jobbie then the smoothing cap may be shot and passing A.C. ripple, just a guess.

Put your meter on A.C. see anything? If you do it's the cap.

Str.

alpard:
Great idea on reading AC from the output DC. If the smoothing cap is bad or diodes are bad, then it will show
solid AC voltage readings.  Will try that.

I don't have the schematic, and couldn't find it anywhere.

M0DOU:
Just found this post after measuring two acquired Icom AD-55 power supplies to check voltage and polarity was correct before using it on my Icom R75 receiver.

Both measure around 20V output. This does seem a bit high but might be by design, if you look at the circuit diagram for the R75, the input voltage goes straight into a couple of voltage regulators (14V and 5V).

Checking the datasheets for these shows they can handle up to 30V input which is well above the 20V input.

Still, I'm a little surprised and disappointed, I'd have expected the NS-55 to be properly regulated at 13.8V given it is manufactured by Icom and is labelled as such on casing.

I probably won't use them as it's only going to generate excess heat from the R75's regulators and reduce their lifetime.

redhat:
Doesn't surprise me.  I've seen more than a few questionable designs come out of icom over the last few decades.  From filter boards that zorch and smoke, to things like this...no thanks.

+-RH

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