KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

[altavek]

Apparently this was a known issue with these speakers. Can't seem to find any info on what exactly causes the problem though. Usually, I would replace the entire board but that is not any option anymore. Was hoping that someone here may have either encountered these specifically or something similar. I'm including pics of the inverter board. Thanks in advance!

[Pentium4]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Please post pictures using the attach function. You should upload some overhead shots of all the boards

[budm]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Straight shot of the top side of the board so we can see the components. Rectifier diodes will be the first thing to check, then the audio output transistors that are mounted on the heat sink.

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Sorry about that. Here's the inverter board from overhead.

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

One more with the heatsink off

[Khron]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Gotta love how the copper bottom layer is silkscreened on the top - easier to trace stuff

Hint: this is the "power board"; inverters are mostly found in UPS's (turning the battery DC into the AC that mains-powered things are fed with) or they supply fluorescent lamp (turning whatever DC they're fed with into the high-voltage AC the lamps need)

As budm said, the first place to check would be the rectifiers - these are the four fat-ish "upright" diodes (D108, D110 and the other two like them, around the two big main filter caps). Just to be on the safe side, you could consider checking the small rectifier diodes too (D101-104, right next to the two white connectors).

Seems these Rokits use some chip-amps to power the speakers -these are the two seven-legged devices that are screwed to the heatsink. What do the markings on those say?

My guess is they're some TDA chips; LM1875's only have 5 legs. A quick search on Digikey turned up stuff like TDA2052, TDA7240 and TDA7298. I kinda doubt KRK went with anything more "exotic" than that

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Both the transistors say TDA2052

How would I test the rectifiers? (Sorry, been a while since electronics class)

[Khron]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Those are $2.47 a pop, from Digikey

Checking diodes is best done with them removed from the circuit (so that other components and connections won't interefere and cause false readings).

You've got a (digital) multimeter, right? Switch that to the diode range (the -|>|- symbol), place the black probe on the "band" (cathode) terminal of the diode, and the red probe on the other end (anode). A good diode should show something in the range of 0.5-0.7 volts - this is the "forward voltage drop" that you'll find in datasheets.

If it's higher than that (unlikely) or the meter goes "over the top", the diode failed open. If it's lower than that (in the 0.00x range), it's shorted

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

So just tested the diodes and the top one of these 4 (D102?) metered 000. So as soon as find my soldering iron, I'll pop it out and get a replacement. Thanks!

Should I go ahead and just replace the transistors while I'm at it?

[Khron]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Mmm... Not just yet. Or better yet, pop all four diodes out, and using the Ohm (resistance) range on your meter, probe between the positive (+) rail and ground, and then the negative rail (-) and ground.

If neither of those shows a low resistance (give it a few seconds before drawing a conclusion, until those big caps charge up to the low voltage the meter provides), then it's safe to assume the two amplifiers are fine (PS: they're not just plain ol' transistors )

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

So I got the diode off. Markings are IN5392 GW. Not seeing this in DigiKey nor does a google search lead me anywhere useful. Suggestions?

[budm]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

It is 1N5392, not I N 5392.
http://www.digikey.com/product-detai...ICT-ND/3711758

[lti]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

If this is a common failure, you shouldn't use an exact replacement. Find one with a higher current rating. I don't think the voltage rating will need to be increased since it looks like the filter caps are rated for 35V. None of the other specs really matter since it doesn't use a switching power supply.

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Awesome, Thanks!

[ben7]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

You could use a diode with a lower Vf, therefore it isn't as likely to overheat.

Also, maybe a 1N5401 will be useful, it is rated at 3A instead of the 1.5A that the original is rated at.

[altavek]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Big ups Budm!

The new rectifier has my monitor up and running like a champ! Guess it's time to get back to work…

[budm]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Great job, thanks for the feedback.

[Boh2k]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Sorry about that. Here's the inverter board from overhead.

Hey New guy here looks like a great place electronic info! So on to what brought me here.

I just was given a pair of rocket 5 g1 and one has (D110 & D108) busted!!
What are these and where can i buy replacements for these?

Thanks in advance!

[vinceroger69]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

can you upload a picture of the part? also has it any writing/number on it thanks

[Khron]

Re: KRK Rokit 5 Gen 1 pops fuses as soon as it's powered on

Might as well replace all four from that set. Going by their "fatness", they may well be some 3A diodes.

If ordering from Digikey is ok, this looks like a good-enough and dirt-cheap option:
http://www.digikey.fi/product-detail...4-3-ND/6022614