[Accorigang]

I don't understand why my luck with DSPs is so dogshit

Today I was /going to/ do an official gain setting on my newly acquired Helix Mini DSP mk2

As I'm about to start I go to unplug the RCAs from the DSP into my amp and the ****in DSP starts smoking

I turn the car off and unplug everything, open the DSP and see this

I have no clue what's going on, I don't think any wiring I have is bad since I've had no other problems, but literally both times I do anything DSP related (EQing on my RF 360.3 then it explodes when Im cleaning everything up) something has to go wrong

I understand the DIY nature of this forum/car audio but God damn man it's just so disheartening dealing with this less than a month later

Is there anything I should do before I set up the next one? I just don't know what could be happening other than poor luck

 

[Accorigang]

Make sure you don't have an rca cable plugged into the positive battery post? Seriously, I'd use a dmm on all of the rca cables getting hooked up to the dsp to see if there's some dc current running through one of them.

I don't have RCAs running "in" to the DSP, just high level speaker signal

I do have 6 rcas running out of the dsp into the amps, would it be possible for an amp to feed power thru the input rca plugs?

 

[Accorigang]

You shouldnt hot plug rca cables

Where were you 5hrs ago lol

Is that standard practice? I've had no issues doing that before in any of my other cars, granted I've only been in the diy audio stuff for a couple of years

 

[Accorigang]

Man that ****ing sucks. I can be pretty careless, have blown a speaker or 2, but have yet to smoke a DSP.

Both DSP's did the same thing? In the same car?

Not the exact same, the 3sixty.3 blew a resistor, the Helix looks like it blew some IC,

The 3sixty had nothing going on when it blew, just sitting there

The Helix when unplugging RCA cables

 

[Accorigang]

Is dsp ground solid?

It's grounded into ground distro into a 0ga to bare chassis, I think it's good

 

[Accorigang]

What vehicle/setup is this used in?

First thing to do is use a DMM to check the voltage on those hi-level input signals, should be between 5V to 10V.

2021 Accord, no factory amplification

I'll be checking that voltage in later, however now that I think about it when my Helix blew there was no signal going into the dsp since I hadn't connected my phone yet

 

[Accorigang]

Was your laptop plugged into ac power and connected to the dsp at the same time? I’ve heard of this releasing the magic smoke before. Where are you located?

Nope, only thing different than "normal operation" was me unplugging the rcas going from the dsp to the amps

And I'm in Rhode Island

 

[Accorigang]

That is an op amp for the RCA outputs.. so whatever happened I am assuming it was directly related to you plugging and/or unplugging the RCA output from the DSP.

I had no idea it could damage it if you did this while in use.. i am assuming one part of the RCA disconnected faster than the other.. or the positive center touched the negative outside of the RCA.. something.. that something I am not sure but i do know thats an OP1678 its the same output op amps as my helix DSP ultra.. which is pretty cool im surprised the mini uses that nice of op amps.. they are from the same family as the burr brown ones from texas instruments and one of the nicest fet op amps you can get.

the one to the left im guessing thats a 4 channel (quad) op amp "OP1679" and then the one you blew is the two channel op amp "OP1678"..

so I am guessing only four out of six RCA output channels are working.. but i would not even operate it in its current state.. it could cause more damage if something is shorted.

The rcas plug touching the barrel is entirely possible as I'm thinking about how it happened, I wasn't very careful in unplugging and just kinds yanked them out

I'm glad for the info you provided, assuming if that's the only thing damaged it could be repaired? I looked around the board and that's the only thing I saw burnt, no other caps and such looked bad

 

[Accorigang]

It can probably be repaired... you need experience and a good hot air rework station to desolder and solder surface mount components like that.. so definitely do not try doing it yourself..

there are some guys who upgrade the op amps on the helix DSPs (i cant remember who) you might be able to get one of them to swap it out but i don't know if it took out any of the components around it too...

i think the best idea would be to send it back to audiotech fischer or msc the american distributor for helix. they will send it to Germany.. although international shipping is not super cheap.. it could be cheaper to reach out to some people in the US that do repairs and see what they say.. I don't know any off the top of my head but i know I've heard of people on facebook and here talking about a few different people that do repairs on amps, or op amp upgrades on dsp's.. so one of those people might be able to swap it for you (granted the surrounding components are not also damaged... i think that is a resistor below it and it looks a little toasty.. if that is a resistor the numbers on it look to be the same as the ones to the left of it.. you can test its value and compare it against the one to the left.. to see if its still goood..

i circled the two i am talking about.. you can test them with a basic multimeter on the ohms setting

View attachment 337417

Yeah I also noticed that resistor pair below, good eyes with the similar pair to the side, couldn't find a schematic but those being identical would make some sense...
I tried contacting audiotech but looks like they're closed on weekends

I'll look into anything in the US as far as repairs go, really appreciate that info with people who work on them

Worst come to worst the item came with a squaretrade warranty so I can hopefully fall on that, just sad not having music for the time being

 

[Accorigang]

DSP mini mk2 with squaretrade warranty rings a bell... it isn't this one by any chance?

FS: BNIB Helix Mini DSP MK2 w/2yr Warranty

I had originally picked up these units before I completely thought out my build. The seller I got the Helix from is looking to give me a bit of a run around returning it. I purchased it from a recommended eBay seller I got from a few posts here (audio_for_fun ) but even though I just received...

www.diymobileaudio.com

Then I would push for that warranty by any means possible.

Thats the one, literally less than a couple weeks with it

 

[Accorigang]

Did it work when you first got it?
In other words; did it play for a while, and then fried after listening to it for a while (after hot pulling the RCA's)?
Or was this the first time you hooked it up, and it cooked the very first time you used it?

Yeah worked flawlessly until this incident

 

[Accorigang]

Hey if that's the one then you should be good to go.. squaretrade should pay out, I have used it before. Just read ALL of the terms and conditions before even contacting them.. i do not know if the warranty is transferable, so check that in the terms or ask them before making a claim. if it is not transferable have the guy you bought it from make a claim.. i can almost assure you that the square trade route will be cheaper than sending it back to ATF since square trade normally pays for shipping.. and in most cases like this where they don't have the capability to repair it they will normally just pay out cash for it granted you do not violate the terms and conditions of the contract... if its just a regular warranty and not accidental coverage i would shy away from saying anything about plugging or unplugging the RCAS..

you or the original purchaser should contact square trade (after reading the terms very thoroughly)

they will send you a shipping label and have you send it back to one of their "repair centers" to evaluate it

what this really means is they are probably sending it to their facility where an insurance adjuster glances at it to see if they can fix it for cheaper than the payout amount is.. in this case they will not have the capability of fixing it if I had to guess.

they will probably ask you a bunch of questions, and should cut you a check for the amount of the original purchase price.

what they will definitely ask you is if there is a manufacturers warranty.. because the square trade warranty is only good if the manufacturers warranty will not cover it.. in this case it will not because helix only gives a warranty if you buy from an authorized dealer in the united states.. So you might be able to send it back to the guy in Europe that sells them on eBay.. but I doubt square trade would be ok with sending it to anybody other than the OEM manufacturer unless its one of their "authorized repair centers" .. so if you get an email from audiotech fischer or MSC (american dealer for helix) saying "no there is no manufacturers warranty because you bought it of ebay" then you should be able to use the square trade warranty.. but once again, I would probably leave that part out unless asked about it... i would simply tell square trade there is "no manufacturers warranty because the manufacturer is in germany" and they can check that themselves if they really want to. worst case audiotec fischer will accept it and make you pay for repair since it does not have a manufacturers warranty in which case square trade is supposed to pay for shipping and the repair (good news for you since international shipping is insanely expensive)

square trade advertises their warranty on eBay when you buy an item listed as "brand new" so they should honor that warranty since that warranty was bought in conjunction with that product as an add on with the sole purpose of being used for that item purchased on ebay. so there is no way they can say "oh its not valid because there is no manufacturers warranty." They can only burn you if you violate the terms somehow and that's why you want to read them very well.. but like i said, i would leave that on a "need to know basis" (regarding ebay not being an authorized dealer)

anyways.. this is just based off my experience which was also something i bought on ebay and used square trade.... but yours may vary.. but i suspect after a few questions and back and forth they should cut you a check.. (just leave out the part about you plugging or unplugging the RCA. adjusters look for reasons to not pay claims and that could be one. you don't want to mention anything about anything being an accident or possibly your fault,.. that's game over for your claim. keep it to the bare minimum of what they require and get your check)

View attachment 337482

Really appreciate this run down, I'll be contacting square trade tomorrow and seeing what I can get done

 

[Accorigang]

It's your own fault from very bad practice.
NEVER EVER hot plug RCA leads , that would be the quickest way to blow your speakers if there isn't a good connection straight away (floating input) , friend of mine blew some expensive pro pa tweeters setting up for a big function doing exactly as you did , whenever you disconnect or connect anything electrical ALWAYS ALWAYS disconnect the power first or at least make sure it's powered off , you are just asking for trouble and have just been lucky so far.

If you were in Australia I could have fixed that for you , very easy to replace the ic with a hot air rework station like I have at work and I deal with surface mount components ( 0402 and smaller ) all the time as I'm an electronics tech.

Thanks for the heads up, I've honestly never heard of this advice and wish I saw it sooner, I very often use to do that without consequence, guess it's a lesson learned

 

[Accorigang]

I'm not an EE, but I do design stuff as a hobby (professionally I'm a software guy).

I mostly agree with yobbo7 - if hot-plugging a RCA causes a device to fail (especially in the manner that this one did, where an IC lets out the "magic blue smoke") then it was indeed designed by morons.

However - the speaker damage thing is a real possibility; as you can end up sending a nasty high-power transient into a tweeter that just can't handle it. Functionally, it's the same thing as driving the amp into clipping, hard.

Based on the apparent damage; it looks like that op-amp chip developed a short across the power rails. A transient across the output pin usually won't do that - you could very well destroy the ability of the op-amp to produce an undistorted output signal - but making a continuous short between the positive and negative rails is unlikely.

I think you just got unlucky.

BTW - some connections are specifically designed to accommodate hot-plugging: MIDI ports, Ethernet ports; most RS232, RS422, and RS485 ports, USB ports, many (but not all!) VGA ports, headphone jacks, and some PCI slots (typically found in server-grade machines where you want to avoid having to restart the system to replace a failed card) all come to mind. You probably wouldn't find it in serious use today, but the LocalTalk networking system used by classic Macs was also hot-pluggable; but the ADB keyboard & mouse ports weren't - you could fry your ADB chip on the motherboard by plugging in a keyboard or mouse while the Mac was on (fortunately ADB hasn't been a thing since the late '90s - it's all USB or Bluetooth instead).

Here's something I just thought about

Sometimes when I would be doing stuff I would get a little shock if I touched the amp (that was being unplugged when DSP started smoking)

It wasn't always, I attributed it to maybe the clothes I was wearing building up a charge along with cloth seats in the car

If its a problem with the amp not grounded well, the static charge on the amp casing could have traveled into the DSP via the RCA

The op amp that's burnt is a 2ch, looking at the dsp channel A and B look to be run by this chip, and the same rcas were the ones being unplugged when it started smoking...

 

[Accorigang]

Do you remember if you had a similar situation with the RF dsp? I was also wondering if it could be a problem with the amp?

When the RF gave up it wasn't being handled at all, I had just completed a little EQ session and while cleaning up I heard a pop when I put up the rear seat (where it's mounted)

It still worked after the pop as music continued playing, but it did not turn back on the next day

 

[Accorigang]

ESD damage usually isn't severe enough to induce smoking - the chip usually just stops working right.

What I'd like to know is if any electricity should be getting onto the amp case, in my mind there shouldn't be

Which would point to bad amp ground right? Either an issue with my ground or the amp itself?

 

[Accorigang]

It definetly not OPA 1678 because there is no O nor A; actualy its not clearly seen which letters are in front of numbers nor manufacturer. Resistor array, numbers on IC and taking in account its only one (OP amp should be atleast one per chanel); my first guess would be RTC.

But its just a guess....

Would the fact that that little array is right behind the A and B channel rca outputs change anything? To the left is OPA1679 which is a 4ch chip and similarly behind channels C-F rcas

xxx1678 is visible, I'm not super well versed in DSP internals and such but to me it would make sense for it to be an OPA1678

 

[Accorigang]

I would never have thought hot plugging an RCA would have caused this but it’s almost certainly not a coincidence that the op amp involved in the output RCAs blew while he was messing with the RCAs.


It is definitely for the outputs not the inputs, here is some pics from my DSP Ultra, it has one OP1678 per two channels so six dual op amps for 12 total channels.


i honestly have no idea what would have caused It, maybe it was something the RCA was connected to on the amp, or it got hooked up somewhere it should not have.. but it’s wayyyy too convenient that it’s that exact part that blew… extremely unlikely they are not somehow connected

View attachment 337790
View attachment 337789

So this is DSP 2 that has busted, I'm going to check today and see if I can trace a similar line between where the last DSP showed damage and if it's connected to the output RCAs

If that's also where it failed I'm thinking the amp is possibly sending voltage thru the RCAs some how...

 

[Accorigang]

It might be an intermittent fault in the amp - 99% of the time it's fine and performing to-spec; but it only has to do it for a fraction of a second to kill a DSP's output stage...

I'm sending the amps back to sonicelectronix for warranty but that's what is currently bugging me, it'll possibly work perfectly for them and claim nothing wrong, but if I get another DSP and it fries Im probably going to chuck all this car audio stuff and go back go stock

Maybe keep the sub

 

[Accorigang]

How much $$$ do you have in that amp? It might be worthwhile to replace it with a different one - even if it's a step down in power and/or quality due to budget constraints.

Lol not a lot, it's an NVX VAD10004, $275 but it's still $275 that could've gone else where