New amp repair project, Autotek MX5000

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Jacampb2
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New amp repair project, Autotek MX5000

Post by Jacampb2 »

Hey folks, I haven't even cracked this bad boy open yet, but I couldn't resist showing her off. I won the bid on this thing on ebay. I was almost sure the seller was going to back out, but it showed up yesterday.

The amp is an old school(ish) Autotek MX5000. It is blown and this is probably going to end up being a pretty big job, but I'll do my best to document it if you all are interested.

I'm really geeked about this thing. I used to run a Autotek MX3000.1 and I loved it. I traded it to another member on here years ago for a blown tarantula, and although I love tarantulas too, it's just not as practical as these class d giants.

I'm working through the end of the week but I'll update the thread with more pics once I get under its lid.

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Oh yeah, I almost forgot the best part! I won the bid a $9.99. Had about $50 into it shipped. As long as it is not a complete write off, I got my money's worth!

Later,
Jason

Sent from my SM-N910V using Tapatalk
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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Jacampb2
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Joined: Sat Apr 19, 2008 11:57 pm
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Re: New amp repair project, Autotek MX5000

Post by Jacampb2 »

Well, I had just a few minutes yesterday to take this one apart. I got kind of sidetracked getting a snowmobile up and running and ready for winter so I haven't done any serious troubleshooting yet, but it looks like the power supply mosfets are blown, these large footprint mosfets are pricey! Anyhow, it did not burn as bad as the MX3000.1 I had before did, that one took a fair amount of patching to bring it back to life.

So, at a glance, I need power supply fets. I should have all the parts for the drivers if they are shot too. It looks like this is at least the second time this amp has blown. The outputs are mismatched. It has half IRF640/9640 outputs and half FQP19N20/FQP12P20. They are pretty much equivalent transistors, but unless I am mistaken they have them mixed in the channels, half IRF, half FQP. It probably isn't necessary for a class D sub amp, but even if the outputs are all still good I am going to go ahead and swap in matching banks. I think it came from Autotek with IRF640/964 parts and I have most of what I will need.

With any luck I will get parts headed this way and work on it next week on my days off work.

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Later,
Jason
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
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Jacampb2
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Posts: 1562
Joined: Sat Apr 19, 2008 11:57 pm
Location: Beaverton 48612

Re: New amp repair project, Autotek MX5000

Post by Jacampb2 »

On a side note, does anyone know if this amp predates the MX3000.1? My MX3000.1 and my MX1500.1 both are labeled made in the USA, and this amp has no labels at all as to point of origin. Also, although the heat sinks are finished the same, this amp is no where near as wide as the MX1500.1. I would be irritated if I were trying to match amps for an install. I am mostly just curious why they would build an amp that is virtually identical to the MX3000.1 but in stead of being permanently bridged like the MX3000.1 this one is stereo. My guess is that the MX3000.1 did close to the 3Kw of it's namesake. I'm thinking the MX5000 succeeded it and is a China or Korea amp and the 5K is the typical pacific marketing wank.

Later,
Jason
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
User avatar
Jacampb2
Mad Scientist
Posts: 1562
Joined: Sat Apr 19, 2008 11:57 pm
Location: Beaverton 48612

Re: New amp repair project, Autotek MX5000

Post by Jacampb2 »

Hey guys, I have a little update. I didn't take any more pictures, but I got all the bad outputs out of the amp-- I am fairly certain they were "ebay specials" almost certainly counterfeit. They were labeled inconsistently and I could see on several that the solder from the die had started to squeeze out between the tab and the case. This can happen to non counterfeit devices too, but it takes a lot of abuse to do it, in the case of counterfeit transistors, a lot of times there is a very undersized die in the case, or simply cheaper low current devices are just relabeled to be a higher rated part. Anyhow, they were trashed so I pulled them all. I pulled all the blown PS fets, nearly every one of those was ghetto installed with the leads not even through the holes. The gate lead on nearly every PS fet burned off in the case. Either mechanical damage from piss poor rebuild from the last tech, or that is just how they failed. I had to replace the BJT pairs that drive the gates and I popped a pair of FETs in each side of the PS and it fired right up. Rails seem a little low at +/-45 Vdc, but I am trying to find confirmation now as to whether that is the correct rail voltage or not.

I'll post back once I get the proper replacement parts in and get it fired up.

BTW, I found the answer to my question above. The MX5000 predates the MX3000 by a few years, and the MX3000 is considered to be the more powerful of the two amps...

Thanks,
Jason
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
ttocs
the Floor Sweeping Hack with Golden Ears
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Joined: Fri Dec 19, 2008 9:53 pm

Re: New amp repair project, Autotek MX5000

Post by ttocs »

it amazed me what they are able to copy now and both how well and poorly they can do it all at the same time....
what else can I say I am a grumpy asshole most of the time.
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Jacampb2
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Joined: Sat Apr 19, 2008 11:57 pm
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Re: New amp repair project, Autotek MX5000

Post by Jacampb2 »

Yeah, it seems that they put a ton of effort into making counterfeit parts, you would think it would be easier for them to just get the right part as factory seconds or something, but that doesn't seem to be the case. The big PITA is that it is really hard to tell which parts are faked. The safest course of action is just not to purchase from ebay/alibaba/amazon, however, there are many Sanken and Toshiba parts that are still in production and simply are not available from first tier suppliers in the US. I have taken the chance on some small signal transistors on ebay that are not available elsewhere in the US-- I have some instrumentation to verify at least some of the transistor characteristics though and so far I have come out ok. I have even bought a few tubes of power supply fets that I will use for testing in an amp that I am not sure if I have found all of it's issues or not. Pop a fet on each side of the supply and do testing. If they smoke, then it a lot less loss compared to the same part from a US supplier. Even a counterfeit part will normally stand up to some initial unloaded testing. If things go well I will rebuild with parts from a known trusted source.

Later,
Jason
M: M100, M44 for a custom amp project
Zx: Zx500, Zx450, Black Zx350
ZxTi: 4 Zx600Ti's, 1 Zx400Ti
Ti: 5 800.1's & 900.7 for a custom amp project. 1 1200.1, 1 1000.2
Tantrum: 2 1200.1's, 1 600.4, 1 500.2
XS: XS6600
ttocs
the Floor Sweeping Hack with Golden Ears
Posts: 14783
Joined: Fri Dec 19, 2008 9:53 pm

Re: New amp repair project, Autotek MX5000

Post by ttocs »

just last night I thought I could use a micro sd card for the tablet I am using. I looked on samsungs site to see what they charges since I have a coupon code and was appalled to see their prices. I went to ebay and was amazed how cheap they are but realized that it was just too damn cheap. 45 mins later after a few searches I was amazed to see all the different vids and articles explaining how to identify fake sd cards and the problems they can cause. I use to work in the semiconductor manf world so I know how hard it is to make that crap so its just amazing to me to think there is a fab(the techy word for a factory that makes chips) filled with people and equipment dedicated to do all that work, poorly and then slap someone elses name on it to give it value....
what else can I say I am a grumpy asshole most of the time.
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