A technical look at the crown MA12000i/ITech series of amps.

Not the usual video we would normally upload, but this details information about the crown MA12000i and I-tech series of audio amplifiers which we can now repair onsite at our HQ in Surrey.

[@barevids]

This video was a huge help in fixing the automotive version of this circuit, the JBL/Crown A6000GTI. Thanks for that!

[@madgadgetuk]

You've got it working now? I saw your comment and meant to reply. Sound like front end cards were damaged. I hope you have done a repair video!

[@madgadgetuk]

Ah I've just seen you have a new video. I shall give it a watch :)

[@barevids]

@@madgadgetuk my issue all along was the headers!! The connection to the pins was really unreliable. I had to remove the plastic guides, squeeze the forks, and tin the pins to make them a little thicker. Would love to hard solder to the board but they're surface mount.

[@fusioneventservices]

@@barevids Yep I've just seen that video now. Interesting as that's not one I've seen myself or heard from the UK service engineers I've spoken to in the past.

[@mikeschupbach7725]

I have a couple if Crown XTI6000 amps on my repair bench. They are very similar, but with much more basic dsp. I was very interested in this repair video, as no techs in my circle have any experience in repairing these. You talk about the IGBTs, but in the XTI6000 they use Mosfets. One point you didn't mention: If the high speed diodes fail, it is important to replace them with matched pairs, hence the numbers that are written on them.

[@fusioneventservices]

Very good point well made.

[@mattmoreira210]

15:05 I've been designing a better, more stable and less noisy version of that topology for a while now in my spare time. One thing that jumped at me at first when I copied Crown's circuitry into a simulator is that the current across the inductors tends to rise into oblivion and drive them into saturation if you don't get the "overlap" adjustment just right - which also drifts a lot with temperature, in a sort of positive feedback. Maybe, there's your answer! My solution was an active PI control loop that continuously senses and compensates said "overlap" - or bias - preventing both inductor saturation as well as operation in class-b, which is undesirable and happens when the bias is too low.

[@byronbridges4753]

Good video 👍. But I need you to do me a favor by handling the driver boards without touching the solder lands to prevent zapping sensitive components from the possible static charge on your hands. I stopped doing that back in 1989. Again, great vid dude👍

[@fusioneventservices]

Valid point, I have however never blown up a component from static in all my years of working with electronics! I must be lucky!

[@jamespeters2859]

I have two of these. Beautiful looking amps. Haven’t a clue how they work. Only paid a grand for each. Dunno why they’re so pricey new. Interesting video. 🙂

[@fusioneventservices]

The complexity of these amps and their market place should be a fairly good clue as to why they cost what they do!

[@jamespeters2859]

@@fusioneventservicesI don’t understand what you mean by ‘’and their market place”. They’re decent amps though, nice n poky! 😊

[@fusioneventservices]

@@jamespeters2859Slow reply, but they are top end touring amps. The price reflects that. Modern equivalents are over £7K now.

[@Bloortomation]

Nice.

[@kevinkinchin1894]

Hi, very informative video. I have 12 of these amps and have carried out a few repairs and learnt a lot too. I have a power supply issue with an Itech 8000. Do you have a schematic of the power supply gate drive cards at all, I have the rest of the power supply drawings but not the gate drives for some reason. Many thanks Kevin.

[@fusioneventservices]

I'll have a look if it's not too late.

[@kevinkinchin1894]

@@fusioneventservices hi no it’s not too late. I still have it in pieces 😂

[@mehedihasan6073]

Very informative and rare video about these series of the amp. Thank you. I am curious to know if the power supplies are segregated for both channels. As we can see there are two sets of red and blue wires and two big transformers. Or all of them are connected in parallel for more current handling.

[@madgadgetuk]

Just one split rail PSU. The coils you see with the red and blue wires are the output inductors in the balanced current drive circuit. They are nothing to do with the PSU. :)

[@mattmoreira210]

​​@@madgadgetukhe's talking about the fact that there are two transformers in the PSU, as well as the fact that the output cable from the PSU has duplicate wires and terminals for each rail. My guess is the two transformers are just paralleled-up, and they're indeed splitting up the PSU's output between the two channels, to minimize crosstalk.

[@arthureschner9319]

Very informative video, thank you. Do you have any experience repairing the power supply of the 12000i? A video of exactly how the psu is working would be great. And...... by any chance do you have / can you share the schematics?

[@mattmoreira210]

Sorry for intruding! 😅 The power supply is an LLC converter that is fed directly from the mains rectifier. It has its frequency modulated in a way as to maintain a more or less constant RMS current flowing at the input, according to the delta between the set voltage and the voltage sensed across its secondary. The only info you're likely to find about it is a PDF underlining its working theory, which I cannot link it here, unfortunately, because KZbin s*cks! 😒

[@ismamoncada1]

any idea where to find service manual for this one?

[@emanuelemanuel5198]

Are there symmetrical supply like +B / -B and GND like in others amplifier like class AB or class H?

[@fusioneventservices]

They are Digital, so the output drivers are only ever on full or off fully. They never operate in any other mode.

[@nelizitopina6714]

hello...I have a question!! Can I use an audio card from the input of an it6000 in an it4000?

[@fusioneventservices]

Yes.

[@nelizitopina6714]

@@fusioneventservices Thank you very much, I changed it and it worked. However, in the DSP menu, the information started to show the IT6000 model and not the IT4000 and brought the IT6000 presets. Does it not affect anything in the limiters and protection parameters???

[@fusioneventservices]

@@nelizitopina6714 Ah you mean you changed the entire DSP input section. Sorry I hadn't realised thats what you mean. It would be worth checking out the larger SMD caps on the old DSP board. They go short. It may be recoverable.

[@juandiegocoloradomesa7027]

Hello, i have in my workshop i-tech 3500, when i connect the standby psu blown the small fuse, this psu go to dsp pcb?

[@fusioneventservices]

Yes. Check the caps on the DSP, they go short across the rails.

[@andyapple9]

I think they over complicated the thing. Thx for the video!

[@xenon9270]

Hello! Can you help me troubleshoot my MA12000?

[@thomaslechner1622]

What did you just say? 405 Volts on a 2 x 200V rated capacitor bank?? I do not believe you!! Or is it 250V rated electrolytics?

[@fusioneventservices]

220v for the itech9000/ma1200i, 200v for the it6000, if you believe me of course.

[@thomaslechner1622]

@@fusioneventservices I believe you, but in case of 220VDC rails, 250 V rated capacitors are needed for sure! BTW: What exact IGBTs is Crown using? Since Class I topology was invented (by Crown's top engineer Gerald Stanley) in order to get rid of body diode recovery problems at all, they could also use MOSFets, like e. g. 600V CoolMos. What is your opinion?

[@mobilered2776]

Hi, I have some with some problem I need schematics, plz can U send me link ..

[@dj_popo]

How would you discharge this safely?

[@fusioneventservices]

I use a 60w 240v light bulb.