Amplifier repair: new MOSFETs / what else? vregs?

[theCybe 5,000+ posts]

The typical 'blown mosfet' amplifier repair;

Any information? Where to obtain replacement mosfets, how to interpret part-numbers/codes - can an amp be improved by replacing the mosfets?

What are the most common parts I'll need to replace?

Any tips?

Thanks.

(( for a silver bx1500d.))

Oh - looks like only one side is blown - typical?

ie;

_ _ _ _ _ _ _

xxxboardxxx

` ` ` ~ ~ ~

Click to read more...

 

[GCAdidas13 10+ year member]

k, i gotcha.

seeing as the problem that caused it to blow is unknown, what you have to fix is unknown. The only reason my repair was successful because i know what made it break, therefore i know what i had to fix.

You can try replacing the mosfets if you wish, and yes only one side of mosfets typically blow. You now have to replace the entire side of mosfets. Partsexpress will probably have your mosfets. Will probably run you $15 plus shipping, or so.

As for which numbers are the part numbers, you just have to try each line. In my case there were three lines of numbers, and the middle number coorelated to the part number.

An amp can be improved by replacing the mosfets, however there is most certainly something else wrong with the board. I'm told by everyone I know and also it was a part of my install, that something else is wrong with the board.

Check for browned resistors and popped capacitors, blackened parts of the board, anything. On the browned resistors check the resistance against other identical resistors on the board with a DMM.

Good luck!

 

[theCybe 5,000+ posts]

Thanks - I scoped it carefully, and it seems that only the mosets, and one resistor are toasty; Judging by the char marks on the board, it looks as though the resistor may just be coated in funk from the blue smoke.

I'm going to guess the amp blew because of a low impedance, and also that this particular amp is NOT as one-ohm stable as they advertised.

What about damage to the traces on the back of the board?

I assume the length of the traces are critical for timing, etc; if I were to alter or replace those traces (ie; jump them to the new mosfets) would I be doing the board an injustice?

Thanks for the reply, I apprieciate it.

Is your board performing to it's fullest?

 

[GCAdidas13 10+ year member]

Check the resistance of that charred resistor against a similarly shaped and colored resistor on the board. Make sure that the colored stripes (that determine resistance of a resistor) match up. If they're equal, you're good, but if not, it needs replaced. RadioShack should have the resistor.

It is a Hifonics, so maybe low impedance could be the issue here, in which case all I believe you have to replace is the mosfets. No harm in trying.

About the back of the board - I only told you to look there because that is where I found that the voltage regulator was fried - the vreg looked nearly fine on the top of the board, but the bottom of the board where the pins stick out was blackened to hell.

As for repalcing the traces from mosfet to mosfet, I don't have the knowledge to comment on that.

My board has been pushing a pair of Magnum 12's in my friend's trunk for a few weeks now, and yes they are loud as hell with great SQ.

Brian

 

[theCybe 5,000+ posts]

Thanks, I'll keep you posted.

 

[theCybe 5,000+ posts]

Part;

______

|__o__|

|fWE21| Fairchild Semiconductor

|fQP(w)| Plant of origin

|65N06| Part Number

`|`|`|` Leads

Found @ mouser.com

$2.33 each; I figure I'll order a few extra, in case I melt some.

Soldering tips?

 

[theCybe 5,000+ posts]

Bump, non-n00bs please?

 

[GCAdidas13 10+ year member]

Shit, I saw this on my user CP but had no time to respond, before I knew it it fell off the CP and I forgot. Thanks for the bump.

Defiitely get a few extra; also see if PartsExpress has them; they might be cheaper there.

As far as soldering goes, I hope you're well equipped.

This is how my repair went:

1. Use cutting pliers to snip off as much of the mosfet as possible

2. Use gripping pliers to grab the existing mosfet's pins on the top of the board

3. Use soldering iron to heat the solder on the underside of the board as you pull up on the pin.

4. Use solder sucker to **** solder out of holes while you hold the soldering iron in the hole from the other side.

Now you have empty holes that your mosfets will fit comfortably into.

5. Drop mosfets into the holes and bend them at a 90 degree angle to replicate how the old ones sat in the board before you clipped them.

6. Use soldering iron and the Flux solder available at RadioShack to solder the bottom tips to the board. Usually as you do this a little bit of solder will seep through the board and give you quite a thorough connection; however it won't seep through the board too much because it dries almost instantly.

7. Some mosfets have resistors right next to them, and one of the pins is connected to that resistor. Before you clip your resistors, examine carefully if your mosfet is supposed to be attached to that near resistor.

8. Now that you have all your soldering points soldered, first make sure to break the connection in the solder as much as you can with the soldering gun and a solder scraper (or small flathead screwdriver). Be sure not to damage the board, and make sure you leave the connection where it needs to stay, such as those mentioned in step 7.

9. Clip off as much of the mosfet's pins as you need to on the bottom so the board will sit comfortably in the case.

10. Apply a few layers of electrical tape if the pins of the mosfets could come in contact with the board case under the board.

Any questions?

Brian

 

[ngsm13 5,000+ posts]

Got mine from a guy off ebay for 59 cents each //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Just type in the part number, the guy I bought from had THOUSANDS of multiple types of MOSFETS //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

NG

 

[theCybe 5,000+ posts]

^ thanks for both of those replies;

I'll investigate the resistor issue, that's the kind of information I was looking for.

Apprieciate it, guys! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Brian; Notice your RE SE is on sale? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[phyphoestilic 5,000+ posts]

Update on this? I own a BX1500D that has fried Mosfets too, I rather repair it than send it into kbaudio and have them repair it for $100+.

 

[theCybe 5,000+ posts]

FETs have been replaced, amp has not yet been tested, but the work looks good.

 

[phyphoestilic 5,000+ posts]

can u give me the exact link for the ones u ordered? I looked on mouser and there was 2 65N06 fet things, so I didnt know which one was right.

 

[theCybe 5,000+ posts]

IIRC, one has a lead-free packaging, and one does not.

As long as it's a 65n06, it doens't matter if it's an FQP or otherwise.

 

[theCybe 5,000+ posts]

I'll check, I might have some spares.