Cambridge audio Azur 740A

[Green Wagon]

Well, isn't life interesting..........

 

I was given that Yamaha tuner and this 740 to repair by the same owner.

I thought the amp would be a quick knock over but wasn't sure about the tuner as I don't have the gear needed to check or align tuners.

Turns out the tuner was a simple easy recap, and this amp *shudders*, it's given more grief than I expected.

To be honest, It was getting to a stage were I didn't think it was repairable.

A previous 'repairer' handed it back, with a bill, saying it was fine. It wasn't. Didn't even make it past it's first turn on self test...........

 

It seems from research, that the 740 (and I suspect a few other models) suffer from the dreaded "DC ERROR".

Lots and lots of people talking about it, no one talking about a cure.

One or two posts about output relays (How does that relate to a dc problem ??) and other just as strange 'cures'. But no definitive cure.

 

 

*** Grrrrrr. See edit at page bottom. Grrrrrr ***

 

EDIT 2 - OK I don't have the cure. No more time or parts will be wasted on this . . . . . . .  Item.

 

This 740 is to smart (HA !) for its own good.

When plugged in and not turned on, it injects ~0.5vdc into the speaker outputs (This is an unloaded voltage).

Once turned on it uses that half volt to test the output loading (speakers) to make sure theres no shorts etc.

At the same time it also tests its own dc offset, along with a few other things.

If any of these are 'not good', the pic controller will turn off two relays that feed power supply voltage to the amp board.

 

Good way to protect itself.

But a @#$%^ that confuses you until you understand what this thing does. Voltage readings just not making sense etc...

Oh, just look at the service manual. Yeah, IF you can find it. This was not easy, but now I have the proper 740 servman backed up in 3 locations.

 

Anyway, blah blah blah yap yap yap. You are my audience, you will pay attention

 

On to the pics. WARNING, If your squeemish, do not scroll down, it gets ugly.

 

 

 

The lower board is actually two boards, they just sit really close and look like one. You'll see this later.

 

 

Awwwwww, do I really have to undo every bloody screw. Turns out probably not, you can remove screws for the amp section and pull it from the top. Not that thats much easier 

 

 

As you remove screws, you can hear 'things' hitting the bench. Hmmm not liking that.........

 

 

 

Oh yes. Pulling screws reveals a bag of angry snakes. front panel and some boards are now free to float where they want.

 

 

Except, all the damn boards are STILL joined by cables, Some heavy power supply ones that are soldered in, others can be unplugged.

So you end up doing surgery on the baby while the goddam mother is still clinging on for dear life to its brat.

 

 

Little soldered in boards. hell why not, I've gone this far, lets have a play with this one too.

Oh yes, the boards, CAREFUL, They do not like soldering irons.

Cheap fiberglass, it contracts with heat, and being double sided with plate through's, you run the risk of it spitting tracks and breaking via's. I had to fix two via's on the main board after I'd done some other work to it.

 

 

Putting it into service mode gives various options, one is to display 'Logged Events'

 

CL is clipping.
DC is dc errors.
OV is overload.
TM is thermal protection.
SH is output shorts.
ON is hours its been turned on.

 

According to this logger, this unit has been abused for its whole life and is ready to self implode.

Do you really believe its had its outputs shorted out 65 thousand times ???

Somehow I think we can pretty much treat the mad womans ramblings as it's own mental issues rather than 'customer abuse'.

 

 

Yes, to do a proper biasing job you really do need to undo and move two boards for access.

 

 

Now were making progress. Two test points per channel, two adjustments per channel, two meters per channel. They affect each other. Little tweek, let it soak, little tweek, let it soak. 2 days. tweek, soak.

 

 

Plugged in, turned off (standby mode), speaker load test is active.

 

 

Turn it on, it test the 'speakers' and other internals, if it's happy, the speaker relays energise and you get the dc output. Um, it has no dc offset adjustment. just the 2 bias trims per channel.

 

 

As I type this, it's now been sitting there playing music for the last 4 hours.

As much as a pain it is to work on (come on cambridge, make your designers actually work on the **** they design) It actually sounds pretty nice..

 

EDIT DOHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH

 

Seems I was premature in announcing it fixed.

It just spat the dummy with a another DC error.

Disappointing as it was on my test bench for ~12 hours without issue.

 

I now officially really do hate cambridge.

 

EDIT 2 - Its dead Jim.

I cannot justify spending another second or dollar on this thing.

 

For anyone contemplating purchasing any cambridge audio product. DON'T.

Edited September 1, 2015 by Green Wagon

[gemini07]

Mate, you're more patient than most of us. My preferred remedy by that stage, might have involved a sledge hammer. Or, if properly insured, a drop/fall from a great height... 

[Green Wagon]

Meh.

Helps I've got multiple things to attend to each day.

Actually got two other repairs knocked out this arv while I pondered this beast.

 

I have been tempted to throw it out the window, Problem is, the security screen would just bounce it straight back at me

 

The small wins I have with other things help placate me to a degree where I don't lose what little is left of my sanity..

 

I was so happy when it was working, Ah well, its good to be reminded you aint perfect now and then.

I'm already planning the next step in its journey..

[Equaliser]

Those Cambridge (and Arcam) units have similar squashed together internals so servicing is a PITA, I just throw them out and don't bother fixing them. The units in particular that have thermal and overload protection circuits are an absolute dog to fix. 

 

As stated, I envy your patience. Which is why when these sort of units go back to Cambridge for repairs, they just throw out the bad modular boards and fit in new ones.

Edited August 20, 2015 by DefQon

[Green Wagon]

yeah this bugger has all sorts of smoke and mirrors. Kinda why I gave a brief intro on its basic motis operandi in the first bit. And then the pic of its 'event log'.

 

best part is, the sm tells you how to update the pic micro code.

But first you have to make a modified pic to board connection cable....................................

 

I got a better idea for cambridge.

 

STOP SELLING RUBBISH. The world will be a better place and I can cut back on my pills for "Muscular and nervous system support"...

 

EDIT. In case anyone cares I think I've worked out why it's being, difficult, So now I just have to wait for the next batch of parts to arrive. Tick Tock. Update when I have one........................

Edited August 22, 2015 by Green Wagon

[Green Wagon]

Last night I replaced more parts.

Spent another 5 ? hours tweaking the bias to be exactly what it wants within 0.1mv.

Even the left and right heatsinks are the exact same temperature.

 

Today it lasted 1 hour before spitting its dummy.

 

Now, it is time for it's Final rites.

 

Its dead Jim.

I cannot justify spending another second or dollar on this thing.

For anyone contemplating purchasing any cambridge audio product. DON'T.

[Equaliser]

No good. Saw this coming though.

[Green Wagon]

Yup.

But us northerners are slow learners

 

Deep down I'm disappointed. Higher up I have to understand that not everything can be fixed. Economically.

[Cichlabxr]

Reminds me very much of some of the aircraft comms gear I've worked on ( in my dim past ). They moved to modular repairs, seems Cambridge do the same. Its a better money spinner for the manufacturers when you have to replace whole boards. Great article though and many thanks for the warning.

[Green Wagon]

Lots of places have shifted to wholesale module replacement.

Sadly it's nothing new.

 

I've sent 'cambridge' an email (thats another utter poo fight right there), if, sorry, when they reply, I'll be sure to let the world know just how helpful they are.

 

I used to repair air tools, one well regarded nail gun maker (american) sold itself to china.

As of that moment, if you wanted a part. lets say a firing valve, you could no longer get just the plastic valve that would fail, you would have to buy the whole assembly. cap, spring, and valve.

A $10 part turned into a $50 assembly. Didn't make it any faster or easier to repair. Just more perfectly serviceable parts thrown into land fill.

Then the quality of the brand took a nose dive.

 

Once I failed at repairing this 740a I did briefly think about deleting the thread, but no, I'll leave it for future reference, and as you say, a warning to others

[Equaliser]

What did you tell the owner about the progress of amp service being futile and unrepairable at this stage?

[Green Wagon]

I've kept him in the loop at all stages.

I've suggested that it's dead and I don't believe its worth pursuing.

He suggested contacting cambridge, So I have indeed done that.

 

>> Still waiting for a reply harmon <<

 

At this stage it is sitting on the shelf while I get my personal projects sorted.

So far the customer has paid for the parts used in the first stage of repair.

I've paid for the second round of parts.

 

I can see that for me to go any further, it will become a time pig.

I would have to enlist the help of the super smarties on another forum, and that is when the device will turn into the bench hog we all hate.

Having to try and test and get readings etc of a device that does not like to be worked on is a barrel of fun.

Did I mention its progressed to an intermittent fault.

 

Before (IF) I go that route, I want to clear all other jobs, and get as much info as possible.

 

It still claims it is clipping. Never pushed it anywhere near that level. Obviously yet another fault deep within. To try and find out what / if it truely is, I will need to borrow a 'scope.

[Equaliser]

I really doubt Cambridge is going to be of any help. Since this unit is quite old, they will either direct you to take it to an authorised Cambridge distributor for repair or parts no longer available and no real options for the repair process other than to throw it away. Or use a doorstop.

[Green Wagon]

Pretty much what I'm expecting.

 

While the locals dig its grave I've gotten my nak receiver finished. Mmmmmmarvelous.

20+ years old, and does what it's told, when it's told.

[Addicted to music]

A collegue at work who is an audiophile from London who had moved here permanently because his wife is Melbournian, the discussion came to the Cambridge brand, a little secret: avoid avoid avoid, not repairable outside warranty.

Reality sets in that even in my line of work board level repair is discouraged, it's cheaper to replaced the card than it is a resistor that's gone open, because they calculate our time as $80/hr, so for you to drive to Jaycar and back, find a space to carry out a replacement, it's cheaper to order the PCB, know that it's brand new and reliable. Agree to this method when all they equipped you is a standard soldering iron and majority of PCBs are now all LSI SMD. Even the fuses these days for input/output PCBs are SMD!

[rantan]

There is always a catch.

 

Cambridge products look and sound very good at their price points but this kind of experience ( which is not unique to Cambridge ) should make people very wary at purchase time, notwithstanding the fact that Australian consumer laws could be invoked in this and other instances ie. a product must be fit for purpose and not just a disposable item after the expiration of the warranty.

Depending on its age, the owner may have grounds for replacement IMO

[Green Wagon]

Ive done my share of multilayer track repair.

smd.

through hole.

vlsi.

I used to repair motherboards when others were replacing them.

 

my issue these days is eye sight.

That and moronic design.

[Green Wagon]

There is always a catch.

 

Cambridge products look and sound very good at their price points but this kind of experience ( which is not unique to Cambridge ) should make people very wary at purchase time, notwithstanding the fact that Australian consumer laws could be invoked in this and other instances ie. a product must be fit for purpose and not just a disposable item after the expiration of the warranty.

Depending on its age, the owner may have grounds for replacement IMO

 

 

Think this line is 8+ years old ???

And I believe the new laws only apply to products bought after ?? mid 2015.

[Addicted to music]

Time to bash it with your idiot stick....

[Equaliser]

It's not just Cambridge, the new Arcam and Nad incorporates the same design and circuit methods. Which is why I avoid the 3 brands for anything that isn't a CD player.

[Green Wagon]

Star date 3-9-2015

Support email sent.

 

Star date 9-9-15.

Situation grim, no response to our communications have been received.

Only logical conclusion is that all, life, in that establishment has been extinguished by disgruntled suckers, err customers err Tribbles.

[Equaliser]

Doubt they will reply back to you anyway. Usually the case when I send an odd job email to some big company. Either they'll ignore you, reply to you month later or so and say they cannot help and direct you to the local distributor. 

[Green Wagon]

Wait, what ?

You think the merest possibility of a speculative thought of an idea of them even having a valid email account that actually receives any form of electronic communication that requires them to even contemplate thinking about replying even entered my thought process ?

Thanks, I love a good laugh.

 

Companies like this I liken to car yards.

 

We got ya money nah nah nah nah nah. *doors slam shut with the sound of dead bolts locking*

[zenikoy]

Interesting piece on repairability from the Wall Street Journal..

 

http://www.wsj.com/articles/we-need-the-right-to-repair-our-gadgets-1441737868

[Green Wagon]

That article makes we wanna puke.

I just can't say anything nice about it at all.