"Audio Refinement" Complete amp blown cap & transistor: Need advice

[mr_macgee]

I have a Audio Refinement Complete integrated amp, It was sent to me with the right channel not working. There are no fuses for the rail/channels, just a main fuse. I took it to a local audio repair guy who I trust, he found a burned out transistor and cap onthe right side. I don't know yet which cap or transistor but the question I have is:

Does it matter that only one side is being replaced? Should the matching left cap and transistor also be changed??

I'm looking to get the most out of this amp.

The tech told me that the transistor was very hard to find but he was able to source one. He said the cap was easy. The price of work he's is charging me is $120.

Thanks for any help. Below is a link to some reference info of the amp from an audiophile in russia who drew up up a spec. and a good schematic of the board

Thanks for the help.

Macgee

Inside Story: Audio Refinement Complete integrated amplifier

[nigelwright7557]

It depends how old the amp is.

If it is old then all the electrolytics will need replacing.

[mr_macgee]

Originally Posted by nigelwright7557

It depends how old the amp is.

If it is old then all the electrolytics will need replacing.

I believe the amp is younger than 10yrs old.

[nigelwright7557]

At 10 years I would be replacing the electrolytics.

A bit depends on how often it has been used.
Some electrolytics have a life of as little as 2000 hours.

[Mooly]

Apart from the outputs which the article says have the numbers sanded off, why not post all the device types when you get it back. It should be easy to spot what has been changed too... it all looks pretty conventional in essence.

Caps... hmmm... maybe getting to a point where you might think of replacement of some. Heat is the killer... a cap rated 2000hrs life @85 C for example (2000hrs... this is quoted at maximum ratings) lasts a lot longer as the heat and ripple current flowing are reduced.
It's a bit like a filament bulb some made up figures but not far off the mark,
1000hrs at 100volt
2000hrs at 90 volt
10,000hrs at 80 volts
40,000hrs at 70 volts

You get the idea.

And should transistors and caps be matched ? If the transistor is the correct type then probably not, if the cap is the correct value and type again, probably not.
Something "in us" makes us feel better when they are though even if we know there is zero audible difference.

[mr_macgee]

Mooly,

Thanks for the response. I'm going over to the tech today to get more info and to dropped off/donate some good used gear I have no use for.

I'll post what I find out and I found out that our local distributor also has a good tech dept. and sells parts.

Not sure if it's worth buying all new caps for this amp. How money is it worth putting into and will it really make a difference in the Bang for Buck? I'm not doing it myself, I having to pay someone to repair it for me.

I bought it used for a second bedroom and was delivered DOA but the person who sold it to me stepped up and has sent me the money to cover the initial repair which was very gracious and unexpected.

Again, Thanks for all the posts and info.

[Mooly]

Your welcome,
Will it make a difference (new caps), honest answer is probably (almost certainly) not... it's as much to do with the feelgood factor of knowing they are all new and will be good for another 10 to 20 years. The cost of parts generally is minimal. The four large caps in the PSU will be the expensive ones if you go for top quality parts... the smaller values... and I can only see a handful on the PCB cost peanuts. It's also important to make sure any replacements are the correct physical size, lead spacing and so on. Any work done should be indestinguishable from factory fitted parts.

Changing caps yourself is pretty straigtfoward with a decent soldering iron... you can always practice on some scrap unit (anything) to see how you get on removing and refitting parts.

Put it in perspective... if the amp has had normal use (few hours a day) and is 10 yrs old it will be fine. If it's never been switched off in 10 yrs, had an owner that covered it with papers and books then perhaps yes, change the caps. Other components won't have deteriorated at all.

[mr_macgee]

Spoke to the horses mouth (Importer), they have been very nice & helpful.

Orig. Parts are available and could be on there way for left and right if I order them, easy fixes. The big caps are fine no damage, he said that they are made by YBA and considered excellent and should have a long life. They are the same caps used in there high end gear and no need to change out unless damaged.

However, The small caps and transistors (non output) will be changed out.

The question I now have, has anyone modified these amps with any success? is it worth getting a certain high end type of small caps & transistors to replace the orig???

I'm going to change out the binding posts (I have good spares) as the orig. are awful for spades. To be honest I don't see a lot to modify or worth modifying. I could be wrong.

Cheers

[Mooly]

Hmmm just noticed in small letters a link on the article you posted to a full circuit diagram with type numbers of transistors apart from outputs and drivers. Can't imagine what the big secret is with those...

2N5551 and 2N5401 are standard "workhorses", cost around £0.05 each for Fairchild devices... and nothing wrong with them at all... I ordered 30 of each a few months back.
MJE340 and 350 have been around for ohhh a decade or three... and are often used even now.

OK... you are not going to improve on this easily. Often a design takes into account the properties of the semiconductors used and so although it's fashionable to say you can use "way better and more modern devices", it doesn't always quite work out like that.
Semiconductor properties of silicon transistors are cast in stone... there is no such thing as an "audio transistor" that sounds better. What folk mean is there is a transistor with slightly different characteristics (higher gain, lower junction capacitance etc etc) that can be put to use in a given application.
Those small signal devices (all the 2n's) may be hand matched to give low DC offset and gain matching... something you can do yourself easily if you buy enough of a device and know what to do... and have the means to test what you have done and see it behaves and performs as it should.

So again the bottom line here has to be to leave well alone.

[Mooly]

In fact have a look at the circuit here in post #2

It's very similar indeed if you look at one channel of the power amp,
Nad 7240pe damaged amp section