Help 15vdc too much

[Snipervision]

I have a 15vdc 10a power supply that is putting out 15.15vdc & of course the item I am powering says it will not work with more than 15vdc. What can I do?
Here is a link to my power supply: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXVCL0&P=7

MRC #RB982 power supply. It is powering a ICE radio Control battery charger.

Thx in advance for any help.

 

[duke37]

Welcome to the forum.

I doubt if 0.15V is significant but a silicon diode in series will drop about 1V. You will need a diode that can take the current that the charger demands and may need a heat sink.

 

[Resqueline]

It can probably be adjusted but I'd need to see its guts in detail to say if & how.
Not that I believe that the 0.15V overvoltage will matter for your item.

 

[Snipervision]

My Ice charger won't run per se as charger says input voltage exceeds 15vdc. Current voltage = 15.15vdc. I will see if I can open the case tonight & snap some pics. Many thx for your help so far. Cheers!

Here is info on the Ice charger I am powering with my power supply. http://www.google.com/products/cata...X&ei=KvkFT6HiO8KMgwfl8NSWAg&ved=0CIwBEPICMAE#

 

[Snipervision]

Here are some pics. If you need different angles or close ups just let me know. Thx again!!

 

[(*steve*)]

Stick a diode in series with your incoming power. It's a very cheap fix.

Ensure that the current rating is sufficient, the voltage rating will not be important.

 

[Resqueline]

Wow, 10 pic's.. Still it was hard to get a glimpse of the vital parts..
First of all, you'll need to service that PSU anyway - since C7 is on its way out.
Next, IC3 is determining the output voltage, together with a couple of resistors (possibly surface mounted, on the solder side).
If you're not up to smd modding the series diode trick Duke & Steve mentioned will also work.

 

[Snipervision]

Would I solder the diode on the 2 outside points & not the high center one where power cord plugs in for inconing 120v?

Could you be a little more specific on the exact diode when I stop at Radio Shack?

 

[davelectronic]

You have what looks like a bad capacitor in there, next to the red ZD markings, in the final output i think.

 

[duke37]

You will need a 10A diode in series with a wire from the power supply to the charger.

The diode will dissipate 10W at full current so will need a heat sink. You may be better off getting a 10A or 25A bridge rectifier which can be bolted directly on a heat sink. You can use one diode to get a drop of about 1V or two diodes to get a drop of 2V (20W).

Voltage rating is not important since the diode will be forward biased.

 

[davelectronic]

Then wait for the bad capacitor to go pop, as if you dont replace it then it will vent, possibly doing damage.

 

[Snipervision]

You will need a 10A diode in series with a wire from the power supply to the charger.

The diode will dissipate 10W at full current so will need a heat sink. You may be better off getting a 10A or 25A bridge rectifier which can be bolted directly on a heat sink. You can use one diode to get a drop of about 1V or two diodes to get a drop of 2V (20W).

Voltage rating is not important since the diode will be forward biased.

Can you elaborate a little more on the 10a bridge rectifier & where it bolts? If I go into Radio Shack & ask for a 10a rectifier is that all they need to know?

 

[(*steve*)]

Ask for a 10A (or greater) bolt-on bridge rectifier. If they press for a voltage rating, say 24 volts or higher.

(One reason for getting this rather than a simple diode is that you can be almost totally sure a bridge rectifier will be isolated from where the bolt goes.)

Any reputable electronics retailer should find this a sufficient description. It may or may not be sufficient for Radio Shack though.

Connect the +ve output of your power supply to one of the legs marked "~", and then your new +ve output will be the "+" leg of the rectifier. You may need to use spade connectors if it is not possible to solder directly on to the terminals.

 

[duke37]

Radio Shack have a bridge rectifier, 25A 50V #276-1185 $3.49, which should do. Remember that this will dissipate quite a bit of heat so will need boltng to a heat sink if used at full current.

While you are at the shop, get a capacitor to replace the dodgy one as others have said.

Have you thought about putting a light load on the power supply to see if the voltage drops within your specification?

Have you had a look to see if there is a trimmer (potentiometer) to set the voltage of the PSU?

Have you checked your voltmeter to see that it is accurate?

 

[Snipervision]

I purchased a 50v, 25a, 1.7v drop, 100ua bridge rectifier as per duke37 from Radio Shack. The opposite corners are marked + & - & the other opposite corners are marked ac & ac. If I am correct you take the positive output of my power supply & connect it to one of the corners marked ac & the rectifier + is my new positive output?? How did you know the capacitor was bad...the one by the "ZD" symbol. It looks just fine. When I check the output with my meter it read 15.35vdc. Thx again everyone.

 

[(*steve*)]

The capacitor has a domed top. they should be flat. This indicates that bad things are going on inside it.

You won't be able to measure any change on a multimeter (or frequently even on a capacitance meter). An ESR meter will show a degradation though.

Connect the +ve output to one (either, or indeed both) lead marked AC and the + lead is your new +ve output.

If this is insufficient, connect the +ve output to the - lead on the bridge and use + as your output. This will give twice the voltage drop.