Help me with burnt board/$35 ms275

[ajaye]

So I finally got around to recapping this zx350, and removed the 2 roasted resistors while I was at it. I don't know what to do now, is this something I can work around/address easily? Appreciate any input on that. I didn't want to start 2 threads so I'll show off my ms275 and ask for help with that in post 2.

[ajaye]

I got this off a craigs list ad from a guy that lived a couple hours away, he sold it to me as-is for $35 shipped and so far I'm not complaining. Clearly the caps have puked a bit. There is also a blown diode near the caps...any idea what could cause that? I also noticed, and you can just barely tell in one of the pics below, that the insulation of the remote lead where it connects to the board is a little discolored. Could shorting it to ground have opened that diode maybe? I'm just guessing, but would like to know so I know what to keep my eyes open for if anything. Also as you can see there was a strand or two in here lol. They were mostly stuck in the thermal past where the devices and the heat sink meet, but I'm assuming there will be more when I get the board off, I don't want to remove it until I'm ready to do the work and have everything to replace so I don't forget how to put it back together

[trickyricky]

Reverse polarity could have cause that diode to pop.


In the 350 , clean it up real good and place new resistor just a bit off of the board.

[ajaye]

In the 350 , clean it up real good and place new resistor just a bit off of the board.

I was hoping that's what you were gonna say thanks a lot man for all your help so far.

[zeropoint0.5]

i would not worry about a blown diode or leaking caps....

i've bought worser damaged amps before.... take out the burned components/leaking caps and clean up the board.....

don't forget to put in new silpads on the ms amp.....

when you think you're finished, please always start to power the amp up with a 10A fuse....in a worst case the fuse will blow....

i once had two traces burned by powering it directly on a 30A fuse so it is better to start first with 10A......

if it does blow there will be more damaged then what you visually see....

you'll love the amps when there back fine !!!!!

[ajaye]

i would not worry about a blown diode or leaking caps....

i've bought worser damaged amps before.... take out the burned components/leaking caps and clean up the board.....

don't forget to put in new silpads on the ms amp.....

when you think you're finished, please always start to power the amp up with a 10A fuse....in a worst case the fuse will blow....

i once had two traces burned by powering it directly on a 30A fuse so it is better to start first with 10A......

if it does blow there will be more damaged then what you visually see....

you'll love the amps when there back fine !!!!!

Oh hell no for $35 bucks even with the minimal work needed (that I know of so far) I stole it! I want 1 more, then I'll swap out what's in the car now for the 2 275s bridged for the fronts and the zx on the sub(s). They are actually somewhat similar in shape I think it will look sharp w/ the zx between the 2 275s, on top of the performance gain I'll be getting.

[valeks1]

Replace two resistors with 1/8 Watts 100 ohms 5%

[valeks1]

You have bigger problem with MS275. B+ and B- was connected backwards. Try remove that diode, and if amp didn't work after that than you will need replace lots of components.

[ajaye]

Replace two resistors with 1/8 Watts 100 ohms 5%

Valeks my question is every zx schematic I can find shows those as 100k (pretty sure, I haven't traced the melted spot one back yet but it appears to go to ground.) I have some 100 ohm 1/8 watt here so it would make my life way easier but im just wondering why that value? Appreciate your advice so far as well.

[valeks1]

100 ohms is part V.2 modification.

[trickyricky]

Valeks, is this just for the ZX or for the ZX-ti's as well? I ask because I've notice my ZX'ti's have the same 100k ohm resistor....Haven't checked the TI's but am sure their 100k as well.

[ajaye]

Valeks, is this just for the ZX or for the ZX-ti's as well? I ask because I've notice my ZX'ti's have the same 100k ohm resistor....Haven't checked the TI's but am sure their 100k as well.

Yeah mine went in for the V2 upgrade when the original owner blew it up and I got it from him when it was finished, still have the paperwork actually. I've seen enough on the forum to feel confident in taking valeks' word, but I just like to know why from a learning how this shit works aspect.

[trickyricky]

Valeks, is this just for the ZX or for the ZX-ti's as well? I ask because I've notice my ZX'ti's have the same 100k ohm resistor....Haven't checked the TI's but am sure their 100k as well.

Yeah mine went in for the V2 upgrade when the original owner blew it up and I got it from him when it was finished, still have the paperwork actually. I've seen enough on the forum to feel confident in taking valeks' word, but I just like to know why from a learning how this shit works aspect.

On ZXti's? Or your just your ZX? Any ideas on the TI's?

[ajaye]

Valeks, is this just for the ZX or for the ZX-ti's as well? I ask because I've notice my ZX'ti's have the same 100k ohm resistor....Haven't checked the TI's but am sure their 100k as well.

Yeah mine went in for the V2 upgrade when the original owner blew it up and I got it from him when it was finished, still have the paperwork actually. I've seen enough on the forum to feel confident in taking valeks' word, but I just like to know why from a learning how this shit works aspect.

On ZXti's? Or your just your ZX? Any ideas on the TI's?

Sorry, I meant I don't know either...I couldn't tell you if my zx even came back from PG with 100 ohm in those places or still had 100k ohm, they were too toasty to even try to decipher it. All the paperwork said if I recall correctly was "V2 upgrade, replace board" or something to that effect.

[valeks1]

ZX-TI and TI also use 100ohms resistors between RCA Ground and Audio Ground.