Creek 4040 help please!

[mole42uk]

Originally Posted by bikelectro

On my diagram, for an early one I repaired it states something about capacitors needed removed if you fitted other than Phillips transistors, or vice versa, it caused the output pair to blow on the one I was fixing, I think it was BD139 that had to be philips - I can look it up this evening. This was over 10 years ago, but it caused the output pair to instantly blow on switch on.

The BD139 tests okay and hasn't been changed. They both have TFK manufacturer codes.

I would be interested to see any service information though,
Creek have done well, but they aren't really able to support a 30-year-old product, especially one that has seen so many iterations!

[Radio Wrangler]

Originally Posted by mole42uk

For RW's amusement I attach part of the v1 circuit for the 4040 amplifier.

Oh dear heavens!

No bias on the output Darlingtons. Base joined directly to base.

Shunt feedback and a 2-stage VAS.
No catching diodes.

I have a strong opinion that manufacturers really ought to do all their learning and developing before putting things on the market.
I thought that long before the middle eighties the business of how to design a reasonable performance audio amplifier had been pretty much sorted. Various firms had made all the likely mistakes and everyone had learned from them.

I wonder what they were trying to achieve by doing things so differently?

There might be a mains transformer worth saving....

David

[snowman_al]

Richard,
We have all been here, the fix it / scrap it dilemma... there is a cost to fixing it, but you might learn something, or scrap it and wonder if it was a simple fault.

Sorry if this is teaching you to 'suck eggs' but if you do continue to try and fix it, it is good advice to replace all the transistors and 1N4148s in the faulty side. Testing them is not the same as the dynamics in use. I would be suspicious of the electrolytic caps too, to the extent of testing each one out of circuit.

I would also buy a bag of 1/4 watt 10 ohm resistors and fit one in place of the HT fuse. Good chance it will go before the darlingtons if there is a fault before them. A lamp tester is almost a must in these situations too.

My preference for the output pairs is the BDW93C and 94C from Fairchild. I have restored a quite a few Nytech and Ion amps that use similar devices and have found them reliable.

Good luck! Alan

[snowman_al]

Oopps, a bit dropped off?

Originally Posted by snowman_al

I would also buy a bag of 1/4 watt 10 ohm resistors and fit one in place of the HT fuse. Ideal to measure the voltage across to calculate idle current or show a fault etc. Good chance it will go before the darlingtons if there is a fault before them.

[bikelectro]

Despite all the criticism i would urge you not to give up! I have never heard bad reports or any reliability problems with these except:
The controls are poorly supported and they can break with rough handling.
The insulators on the O/P transistors can cause crackling if they break down.
I had mine in use with not too efficient large speakers and played loud and it has never given trouble! This is a cracker sounding amp.
I’ll try to put the diagram i have on here, this is for early models like mine from early ‘80’s ( model was launched in about ‘82 , mine is ‘84 )
In the top corner it states ; “C25 is essential if original Philips Q6 & Q7 are not used”. I was wrong about the BD139, these are the O/P darlingtons, so do check this out! I remember now what happened, i was checking things and had accidentally left the cap disconnected and it blew O/P’s on switch on.

[bikelectro]

Looking at your pic, mine is a bit different and i cannot see the small caps, same capacitors coupling the speakers - it is a similar later version. I would take a chance on swapping the O\P pair from the good channel - if it is stable then you know you need to source better transistors? You can do this before giving up and it wont cost to find out!

[ekjdm14]

Originally Posted by bikelectro

Looking at your pic, mine is a bit different and i cannot see the small caps, same capacitors coupling the speakers - it is a similar later version. I would take a chance on swapping the O\P pair from the good channel - if it is stable then you know you need to source better transistors? You can do this before giving up and it wont cost to find out!

Or alternatively, if the OP already has a replacement output pair on hand perhaps he could try fitting these in the good side and see if they work. Better than risking the original parts if there is a fault present.

I'd also echo the advice to replace all the transistors in the faulty side despite their testing OK. They can and do break down under working conditions where they don't in a tester.

[Silicon]

If one of the bias diodes goes open circuit intermittently, the output transistors may pass a high current and then fail.

You could temporarily wire some diodes across the existing ones on the PCB, to act as a backup.

[ajgriff]

The first half dozen paragraphs of Creek Audio's history, as described in the following link, go a long way towards explaining the unsophisticated nature of the CAS4040's design in its original guise:

https://www.creekaudio.com/history/

The company's founder, Mike Creek, had a background in the production of cut price consumer electronic goods and clearly came up with the CAS4040 in that spirit ie, the amplifier was built down to its £100 price point. It would also seem that Mr Creek, working from his spare room at home, did not at that stage have any real technical/design background.

For me the amplifier would be of some historical interest in hi-fi terms and might be worth restoring as such. However, it's not an amplifier that should be considered for serious use.

Alan

[Radio Wrangler]

That explanation is a perfect fit to what can be seen in that progression of amplifier designs.

David

[dave cox]

If it has a split rail supply I would be tempted to fit a couple of LM3886 amplifier modules as its quite a neat looking small form factor unit! Its possible to use LM3886 on a single rail but it needs a few more components ...

dc

[Marconi_MPT4]

I would be very wary of 'replacement' Darlington transistors, having had problems with third party products bearing the same type number. Compared with original Philips parts, the new devices had abysmal switching performance and failed through overheating.

During the 1970's many audio manufacturers used Darlington transistors and I recall the fun and games with many of the B&O amplifiers that went into thermonuclear meltdown. As others have suggested, you will definitely need to use a variac or connect a series resistor in the DC supply line to limit damage by the output pair going immediately short circuit during investigation.

Rich

[bikelectro]

Just to say again I think this is worth fixing despite its naive design. I think they got away with these design errors as they don’t have a bad reputation.
I remember these being described as the poor man’s A and R Cambridge A40. Cost only half as much but sounded almost as good! Mine had 30 years hard loud use and sounds great still but in a second system . Note that it may have no sign of previous repairs and has lasted this long as have others that come up for sale.

[bikelectro]

Sorry, meant to say A60.
When mine was 10 years old, I thought my system needed upgrade - I thought the amp was the weak part and brought it and my speakers in to a local high end dealer. He told me to keep the Creek and I changed the speakers which turned out to be the problem.

[Radio Wrangler]

Prices when new aren't that important now. If you keep your eyes open you can pick up all sorts of amplifiers for pocket money. Valve stuff, especially anything with a cult following, can be pricey, but transistor stuff can be found for very little. I've had Quad 33/303 and Cambridge amps given. A bit of sorting and I've given them to people who would enjoy them.

If you're going to put in the effort to fix an amplifier and source non-fake transistors, then you have a lot more choice in the starting point than you could ever afford back in the day.

Those Creek amps have made it onto my 'do not resuscitate' list. A bit too marginal in design to bother with when I can find better candidates for no more money.

If someone else wants to sort one, I'm happy to provide guidance. But my aim is to help the repairer learn about circuitry. The amplifier is much less valuable.

David

['LIVEWIRE?']

As an aside to all this, didn't Mike Creek design some of Cambridge Audio's amps, or parts thereof? Earlier this year I repaired an A3i for someone, and I'm sure the pre-amplifier board had 'Creek Audio' or 'Mike Creek' printed on it.

[ajgriff]

There was I think some collaboration between Mike Creek plus associates and Cambridge Audio in the design of the A1 (circa 1998). I imagine therefore that there may have been some Creek involvement in the design of other Cambridge products around that time. All a bit odd really.

Alan