JBL Crown Monster A6000GTI

[Dr Zeus]

I got the amp which I had previously seen at another local repair shop several months ago which I posted about here: JBL 'Crown' A6000GTi - Thats a HUGE b* - diyAudio

The repair shop - since they do this type of thing for money - didnt have the time nor attitude for fixing this monster one-of-a-kind amp; so they had returned it to the customer with the diagnosis of a failed protection system. I guess I'm getting rather good at fixing most of these amps, and word gets around. I got a call yesterday from a guy of a friend of a shop I'd fixed a few amps for and received the all-mightly for a repair attempt this morning.

This thing is HUGE! I mean, it is probably physically the largest amplifier almost ever built. Its girty and massive, and makes the trunk of my car look like a Formula1 engine:



Cheers to the amp gods for bringing this piece to me. Not only would I like to fix it, but I also want to offer this amp to questions of the cummunity. I really plan on doing a bit more than the regular repair here. I'm wanting to try and do as much R&D to really discover this thing, and questions/answers for anyone. For me, this one is about the hobby and not the business. I'll probably have this amp in my possession for about a month as the story from the owner is just as fascinating as actually touching this monstrosity.

This amp was practically pulled out of a land-fill. The As the story goes, the amp along with several other JBL 6000GTI amps were brought to a local scrap yard here in Atlanta, GA after either: 1. they were prototypes with design flaws, 2. they were end of life and past the time alloted by jbl to sell, 3. someone made a big booboo and tossed them away. The owner of this amp knew someone working at the scrap yard and was able to grab one, FOR FREE!!

Unfortunately this amp suffers from what kind of sounds like a prototype or ill-fated common death of the protection system.

Before I launch and break open this beast I'll first need to reconfigure my actual workspace. I dont even have room, and I'll likely need to get my 75A power supply in the mix for testing.

Cheers!




I've taken some more pics which can be found here: http://s886.photobucket.com/albums/a...emeat2010/jbl/

[timwebb]

is that big thing the transformer?

[Dr Zeus]

It sure is. The transformer is approximately 6" in diameter and is of similar girth to what you would see in something built for high-powered supplies. The 'outer ring' is a ring of electrolitic stiffening caps. Between the transformer and the ring of caps lies the power supply transistors oriented in a circular arangement with the legs of the transistors pointing twards the caps. I was doing some reading and found that this amp may be able to produce +-170 rail voltage or switch between high-current and high-power.

Cant wait to break it open.

The transformer looks similar in size to something like this:

[quazy]

Glad to see you got one...mine still needs work. Could you tell me what caps you would recommend for the straight row right under the jbl logo. I believe they where 200v 120f. Im probably wrong and i dont have the amp with me right now. I wish i lived close i would just pay you to fix this one also. But unlike yours i dont think my is a power supply issue cause mine doesnt go into protect. Just no out put. As talked about in the video i linked in this post. jbl a6000gti help

[AKHeathen]

heck yah, i wanna know about that thing. when it came out, o heard it was capable of over 300vac,but that, i have not seen. i was told, however, that they used one to not only weld with, but remained stable with the speaker outputs shorted with an 0ga jumpper. anywhoo, i'm curious how the hc/hv switching works, for starters, circuit layout of both main ps and output arrays, gut-shots, gut-shots, gut-shots, and of course, was this person working at the scrap-yard able to come away with any more?

[Dr Zeus]

I've been away for just a bit but I should get to opening up this sucker either tonight or tomorrow. YEAY!

[Dr Zeus]

Finally was able to break the top down. This amp has 48 power supply fets; IRF1405 which is a 55v, 169A fet. There are 24x 10,000uF 35v caps. Each pair of PS fets has a cap! The transformer is ~6" in diameter and sits off of the power supply PCB about ~2.5". Together they are supposed to create some sort of photonic nirvana.

The rail caps are 200v 1200uF rated and there are 28 of them by my count. I am unable to figure out what the output transistors are due to them being covered by some sort of crafty convection cooling ducts.

As wor the design of this amp, it looks very elegant but something very un-nervy. The amp has so much stuff going on inside I'm not exactly sure where to start, so I'll start with what I know - an SG3525AP near the PS fets.

The one thing which stricks me about this amp is it's apparent cooling capacity. Sure there are enough components everywhere to keep things running efficnent, but I thought an amp of this massive size, weight, and stature would have some better arrangement. The main heat-absorbing portions of this amp are not cast, but extra-thick sheet metal. The convection cooling near of the audio side is pretty cool, but the powersupply side seems much less amuzing in terms of cooling capacity.







More pictures can be found here:
jbl pictures by unclemeat2010 - Photobucket

[AKHeathen]

so, there is no fins, or anything on the other side of the board? looks like the fan draws air from the back-side of the power supply. honestly, the arrangement is a tad skimpier and more clustered than i immagined, whic is probably not great for heat dissapation. i would have moved things around quite a bit, if it was me.

[Dr Zeus]

Hey Quazy,

I think I found out why this amp is having some troubles. If you or anyone has this amp handy, could you please take a hi-res photo of the small expansion board with the two TO-220 voltage regulators? I found some damage on the board between the regulators, where it also would appear a previous repair was attempted. I can tell there may be one trace and a missing surface mount cap still not connected correctly here: