ZXti 400.2 leds

Jeroen · Post by **Jeroen** » Mon Sep 29, 2014 9:26 am

Hi there,

Next to my 2 ZPA's I also have a 400.2

The amp is running fine but the leds are not working. I measured the pcb on the top with the leds on it.
29 volts on the powerlines and 100 ohm on the resistor.

Does anybody have any experience with this?

trickyricky · Post by **trickyricky** » Mon Sep 29, 2014 9:52 am

Have you tested each LED? If one LED goes out then it opens the circuit causing the other two not to turn on. PM me if you need some LED's, I have something very close to the same color but just a bit more bright (might have to replace the 100ohm to 1kohm in order to dim it to the same brightness as the original).

Jeroen · Post by **Jeroen** » Mon Sep 29, 2014 10:13 am

Thanks for the help. I don't know how to test them.
It must be a faulty led. The pcb is powered and the resistor
is ok.

trickyricky · Post by **trickyricky** » Mon Sep 29, 2014 10:19 am

Yes faulty LED, if you have a dmm you can set it to diode mode and test each LED. Depending on the dmm's voltage will depend on how bright the functioning LED are, but more than likely it will barely power the LED on so make sure your in a dim room (lights off). Black lead goes to the square solder pad of the LEDs, Red lead goes on the circle solder pad....again keep in mind that the LED will be barely lite, so pay close attention.

Best bet is to remove all three and solder new ones, can't fail especially if you already checked the voltage and resistor.

Jeroen · Post by **Jeroen** » Mon Sep 29, 2014 10:26 am

Ok did the test... and yes 2 of the leds are faulty.

Thanks again.

Are there any specs on the leds. Maybe I can get
them at a local store?

trickyricky · Post by **trickyricky** » Mon Sep 29, 2014 11:07 am

Your welcome.

Don't know what local store your referring to but Radioshack will have a limited amount of LED's size and colors. Fry's electronics (or any other electronics dept) should have a large selection of LED's. Take one of the originals so you can get the right size, last thing you want is to have some bulky big LED's that don't fit through the existing holes.

thedeal7235 · Post by **thedeal7235** » Fri Oct 03, 2014 3:34 pm

I'm in fla and I use Newark element, if u want I can give u the exact part no.; I usually get 12 of them for 4-5 bux-I've done these dozens of time, so much so my little" trick" is to NOT de solder old leads, I cut old led off, then solder led " legs' to the existing ones; the via pads are so small, it doesn't take much heat to pull them off( I learned this the hard way, which is why I use my " trick"& it works for me

vwdude · Post by **vwdude** » Sat Oct 04, 2014 6:40 am

thedeal7235 wrote:I'm in fla and I use Newark element, if u want I can give u the exact part no.; I usually get 12 of them for 4-5 bux-I've done these dozens of time, so much so my little" trick" is to NOT de solder old leads, I cut old led off, then solder led " legs' to the existing ones; the via pads are so small, it doesn't take much heat to pull them off( I learned this the hard way, which is why I use my " trick"& it works for me

Interesting "trick". Someone used that "trick" to replace a PWM on one of my ZPAs that I got off eBay that was non-functioning. I don't frown upon it as much with just LEDs but my thoughts are that you should do it right, don't take shortcuts, even if it's just the LEDs.

Sorry, I'm off my soap box now.

thedeal7235 · Post by **thedeal7235** » Sat Oct 04, 2014 6:59 am

Yeah I wouldn't do it that way with an actual zx's series; only the Ti series , on LEDS only( & I haven't owned a ZPA since 2008,& I sold it to a guy in Russia) Have u ever had to replace ti LEDs? The via pads are so small, prob pull up& off pub with only 70 degrees

trickyricky · Post by **trickyricky** » Sat Oct 04, 2014 7:05 am

It's easy when you got the proper tools, desoldering iron makes thing much easier with it you can remove daughter pcbs with multiple pins like if it were an LED lol. The soldering iron tip has to be the correct size and the temp has to be set just right, its easy to damage via through holes or lift pads when you have a giant soldering tip and the temp set too high.

See no damaged done (I use a scratch pen then MG Chemicals isopropyl alcohol to clean it up), its easy to remove them and to soldered them back on. Once removed you can work on them with ease, no hacks.

Since the LED board is hold with two screws, that makes it much easier to remove and remove LED's....again with the correct soldering tip and heat temp; no damage will be done.

This ZPA got ALL electrolytic caps replaced....again easy when you have the right tools. Even the rail caps are a breeze.

vwdude · Post by **vwdude** » Sat Oct 04, 2014 1:13 pm

thedeal7235 wrote:Yeah I wouldn't do it that way with an actual zx's series; only the Ti series , on LEDS only( & I haven't owned a ZPA since 2008,& I sold it to a guy in Russia) Have u ever had to replace ti LEDs? The via pads are so small, prob pull up& off pub with only 70 degrees

I replaced all LEDs on 3 ti amps actually. Took no time at all and no damage.

I do need to get one of those desoldering tools though, I hear so much about them, nothing wrong with saving time but still doing it right.

thedeal7235 · Post by **thedeal7235** » Sat Oct 04, 2014 1:38 pm

[URL=http://s253.photobuct.com

U mean like this, correct, ( I know, I don't disagree, but shared a tip for what I do, @ this point

thedeal7235 · Post by **thedeal7235** » Sat Oct 04, 2014 1:39 pm

http://s253.photobucket.com/user/thedea ... sort=3&o=8

thedeal7235 · Post by **thedeal7235** » Sat Oct 04, 2014 1:40 pm

http://s253.photobucket.com/user/thedea ... ort=3&o=10

thedeal7235 · Post by **thedeal7235** » Sat Oct 04, 2014 1:42 pm

http://s253.photobucket.com/user/thedea ... ort=3&o=60

thedeal7235 · Post by **thedeal7235** » Sat Oct 04, 2014 1:42 pm

http://s253.photobucket.com/user/thedea ... ort=3&o=61

primergy · Post by **primergy** » Sun Oct 05, 2014 8:11 pm

Thanks so much for this thread.
Timing could not be better!

Found a ZX450ti for $20 at the local Goodwill.
Works, but pots are very touchy, fan and caps need replacement. Already ordered some Elna Simic caps and plopped a Noctua fan in there I had.

LEDs do not burn up that often, so I had suspicions that there is still a bigger issue regarding the dead LEDs.
Tested, 2 LEDs dead.

Instead of going back to the bench, measuring LEDs and browsing in endless online parts catalogs;
does someone here have a part number for a good match?

trickyricky · Post by **trickyricky** » Mon Oct 06, 2014 4:20 pm

It will be nearly impossible to find an exact wavelenght/intensity/radiation diagram, but a good start would be to look for LED's that are; 3mm, around 450-490 wavelenght (color:blue), water/transparent lens.....luminous intensity 800-1200mcd (you might have to adjust it by changing the resistor from 100 or 300ohm to 1kohm in order to tray to match the luminous intensity).

primergy · Post by **primergy** » Tue Oct 07, 2014 1:03 pm

Many thanks. Those specs made finding replacement candidates MUCH easier.

Will order a few of each and see.
http://www.digikey.com/product-search/e ... 60-1603-nd
http://www.digikey.com/product-search/e ... -3lsby4&WT

ZXti 400.2 leds

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