When I bought the icom PS85 power supply one thing inmediatly catched my attention, THE NOISY FAN

You would expect if You pay $450 usdollar (in the Netherlands) that this would be a great power supply and not a noisy one !


Well after 2 day I decided that it was time to do someting about it, after contacting icom I heard that there was no mod. for it so I had to do it myselve.

This mod is using a NTC to sense the temp and control the speed of the fan so the temp wil not exeed 50 degrees celcius.

potentiometer P is used to adjust the lowest speed of the fan (I set P so that the fan gets at least 6,5V at 20 degrees celcius)

I have tested this mod with a ic-756 and it works great, the noise has gone down with about 50% and the PS85 works as good as before the mod.

NOTE: some people have a hard time finding the TAF1453 if you can't find it trie TAE1453, if someone finds a replacement for this ic pse let me know


How to proceed (after building the above)

Remove upper and lower covers.

You must find a place to drill a hole for the NTC close to the diodes

Begin with drilling a hole of 3.5mm (just look on the inside so You wont drill thru a component)

How further up the hole is the better, now You have to tap M4 in the hole (be sure to use a drop of oil)

Now carefully srew in the NTC with a bit of cooling paste on the thread.

Now use 2 sided sticky tape to place the fan control on top of the coil

Connect the NTC, FAN and power and adjust with P the voltage the fan gets (6.5V at 20 degrees celcius)

Just trie it and You will be amazed (and think by Yourselve why did'nt came ICOM up with that idea)

The cost for all of this was just $10 us dollar and 1 hour of work

Thanks to C@rlos for sending me the schematics.

When You turn on the PS85 the fan will start at full speed (to remind You how noisy it can be) after about 2 seconds it will slow down.

I thought about replacing the red LED in the front for a dual colour one so You can see what the fan is doing but decided not to that (yet)

anny suggestions ?

just e-mail me