Johnson Millennium 150 and computerized amp thoughts

[Randall]

Customer brought me this amp with every LED lit up on every switch, knob and display. It did make some sound, and the analog parts worked, but of course no digital. PS functioning, CPU battery good, nothing loose, no change with PA disconnected, no bad smells. The processor board on this is enormous and of course all SMD. I seldom do this, but I buttoned it back up and gave it back at no charge. No way I'm going to troubleshoot that board, and even if I did manage to figure out where the problem lies, no way I'm going to be able to replace the little chip. I need a magnifying headband just to work on analog these days.

I suppose I could have looked into the possibility of procuring a replacement board, but THAT sounds expensive. Too many times I have seen the face of the shop owner I used to work for after installing a replacement board assy., only to have it not be the fix. It's the way things are going to be soon enough I suppose. Disposable. I'd rather sacrifice some of my time for no charge than to get sucked into a long and expensive slog over this computer based gear.

Would you have tried to fix it, and if so how?

[nosaj]

Customer brought me this amp with every LED lit up on every switch, knob and display. It did make some sound, and the analog parts worked, but of course no digital. PS functioning, CPU battery good, nothing loose, no change with PA disconnected, no bad smells. The processor board on this is enormous and of course all SMD. I seldom do this, but I buttoned it back up and gave it back at no charge. No way I'm going to troubleshoot that board, and even if I did manage to figure out where the problem lies, no way I'm going to be able to replace the little chip. I need a magnifying headband just to work on analog these days.

I suppose I could have looked into the possibility of procuring a replacement board, but THAT sounds expensive. Too many times I have seen the face of the shop owner I used to work for after installing a replacement board assy., only to have it not be the fix. It's the way things are going to be soon enough I suppose. Disposable. I'd rather sacrifice some of my time for no charge than to get sucked into a long and expensive slog over this computer based gear.

Would you have tried to fix it, and if so how?

Quick Google search and I would have tried a reset

Should your amplifier start acting strangely as you try scrolling through settings, your amp may need to be reset. To do this turn the amplifier off, hold down the "config" button and turn the amp on again. Wait for about 20 seconds and then press the "mod" button.



Here are some helpful threads regarding picofuses that can fail and cause your description.
http://www.johnson-amp.com/forum/vie...did=1070672226
http://www.johnson-amp.com/forum/vie...did=1093132720

Nosaj

[Randall]

I did try that.

[nosaj]

check the links I just added also.

jason

[g1]

I think you made the right choice. I would have done the same. I'm not SMT capable so quick check for simple power supply faults, then if nothing I can do, give it back no charge.
From the sounds of those threads Nosaj linked, any serious problems would be best dealt with by the factory.

[Mick Bailey]

Although I'm OK with SMD boards, the main problem is the learning curve to repair a one-off item of digital equipment. If I was to specialize in that product, that would be one thing, but I have to look at the billable time that comes out of the background research that's needed. With an analogue repair you're 'just' looking for a faulty component or connection. With digital you have software, firmware and hardware. A software error can mimic a hardware fault and vice-versa.

I've spent many years repairing digital industrial equipment and have been factory-trained in a broad range of products and systems. This means access to code, test procedures, documentation, service updates and inside knowledge. Plus access to spares and replacement boards.

Some of the audio equipment I see is every bit as complex as that industrial gear. The difference is trying to repair it with (sometimes) zero or unhelpful factory support, no documentation and no insight into how the software operates. I see the odds being stacked against the independent repairman. You can look at spec sheets all you like, but that won't tell you what's going on at a software level. If you have an off-the shelf device to replace that additionally needs programming, how will you do that?

I'd take a look at it - stuck LEDS at switch-on sometimes means a failure in POST and can point to a missing voltage or one that isn't there at the correct time. I have a good success rate at repairs of all kinds of gear and rarely get beaten, but sometimes you have to know when the odds are stacked against you.

[drewl]

There are a couple things you can check before going too deep into something like this.
Power supplies as mentioned, missing 5v supply caused that same problem on a unit I had.
Check the clock circuit/oscillator and sometimes the power on clear circuit, usually a timing chip with a cap that powers up the digital board, common problem with products I service in my day job.

As always a little bit of googling can sometimes yield the answer.

[bsco]

I find this type of equipment very hard to repair...no support from manufactures, no documentation, components are extremely small.....a nightmare to say the least..I will take a look but will not spend a lot of time on this type of equipment anymore...I used to spend all kinds of time on these types of repairs...it just isn't worth it......just my opinion......
Cheers

[g1]

What I said about not being SMT "capable" was more in reference to vision and steady hands rather than tools/equipment. I used to be fine with the little tiny stuff but not so much anymore.

[drewl]

Fortunately I have all the equipment for SMD work, and without my contacts in I can see up close better than normal being near sighted.
It's like I was born for this type of work, or I evolved to do it.

[bsco]

Fortunately I have all the equipment for SMD work, and without my contacts in I can see up close better than normal being near sighted.
It's like I was born for this type of work, or I evolved to do it.

My previous employer had all the necessary tools and equip.....two X10 microscopes worth 5 grand each.....8 PACE stations...a ton of different attachments......etc....but I can't afford anything close to that and I don't get a huge amount of that type of repair so it is not feasable for me to get into it to that level.....and you have to have the proper gear to attempt some of it......

[drewl]

You'd be surprised what you can find on the bay or Craigslist.
My friend got a nice Pace soldering station with vacuum and all the smd tips for like $50.

[Jazz P Bass]

The real bitch in my opinion is when they overdo the glue that holds down the surface mount component.
Usually opamps.

You get the solder good & wet & the part still won't budge.

[Randall]

What I said about not being SMT "capable" was more in reference to vision and steady hands rather than tools/equipment. I used to be fine with the little tiny stuff but not so much anymore.

Yep, that's where I am, too. And the more I think of it, this type of problem is akin to losing a motherboard on a computer. Who tries to fix a motherboard?

[drewl]

The real bitch in my opinion is when they overdo the glue that holds down the surface mount component.
Usually opamps.

You get the solder good & wet & the part still won't budge.

Well you can use hot air which melts the adhesive as well as desolders the component.
And the heat gun has different size tips for different chips, ours at work can even suck the component off the board, but I rarely have to use that function.
It was more for production line work.
And if the part is say a common SMD opamp, it's still easiest to clip the leads and lift the body while applying hot air to melt the adhesive.

Yes, I do this stuff alot as you can probably tell.