right hand A & B channel of cambridge 640 v2 amp not working

[admin_exported]

I have got the cambridge 640 V2 amp and cd player, as well as epos m5 speakers in my bedroom, but this morning the right channel of the a and b speakers has stopped working.

 

Does anybody know if this is a known problem etc

 

I spoke with richer sounds and they said it is not a common fault ( doubt that though!)

 

I am more than willing to look at new amps or second hand amp, if it is going to cost to much to mend the cambridge amp.

 

Cheers,

Phil 

 

[Terryff]

I have always found richers sounds staff to be open, honest and well informed. I wonder on what basis do you doubt their statement?

 

[Anonymous]

I have bought alot of items through richer sounds, but my amp broke 3 times, and they told me it was not a fault that they had seen before, and also, when speaking to them about the channel imballance, they said it is not usual, but on all the amps I tried, it was on all of them, and checking on here, it is well known!.

ÿ

I am not trying to bash richer sounds, just either try a new amp, or get peoples views on the above subject.... As this is a forum after all....ÿ

 

[Anonymous]

Take the speaker wire out, turn it on, let it run for a while, check both channels work on the headphone socket, carefully plug the speakers back in, check the connections at the speaker's end and then try again.

 

[Anonymous]

I was just speaking to a bloke that mends electronics and he siad it might be the output section.

ÿ

I will try what you said, but am not hopeful, as tried most things this moning, bar chucking it at the wall....ÿ

 

[Messiah]

Are you sure you haven't adjusted the balance?

 

[Anonymous]

seduct10n:
I was just speaking to a bloke that mends electronics and he siad it might be the output section.

ÿ

I will try what you said, but am not hopeful, as tried most things this moning, bar chucking it at the wall....ÿ

I'm being serious here: If it doesn't work after trying everything and it's out of warranty, give it a firm bang on top. No joke, it worked on my amplifier; if it does work after that, a solder joint has, most likely, degraded.*

*Disclaimer: I do not accept any responsibility for damage caused to electronics, neither on this forum, nor away from places where John Duncan is a figament of our (collective) imagination.

 

[Anonymous]

Your dual output terminals are almost certainly from the same amps. So you have actually only a single channel (right) not working.

Turn the volume up full (with no music). Do you get hiss in both speakers? If so, the problem is between your volume knob and your input source. If you get hiss out of one side your output stage is the likely culprit.

My money is on your output stage. NOW! I had a cambridge audio A1 Mk1 and had to repair it 3 times.

My A1 had output stages fuses which blew on one of the occasions. Your 640 might have the same thing..

So as long as this will not void your warranty, I'd pop the lid and see if there are any visible fuses (usually little 25mm or 50mm glass tubes with metal ends and a thin wire inside). Take the fuses out 1 by 1 and check their continuity with a multimeter (or if you are really desperate and you can identify the two output fuses and just swap them and see if the fault moves).

If it is just an output fuse, then repair is a few pence. If it's actually a transistor that's blown then you gotta take it in really.

 

[Anonymous]

Hughes123:Take the speaker wire out, turn it on, let it run for a while, check both channels work on the headphone socket, carefully plug the speakers back in, check the connections at the speaker's end and then try again.

Whatever you do, don't take out or put speaker wire in while the amplifier is turned on especially if you have audio going through it you will probably get away with it on a healthy amp with no audio coming out but when I unplugged the speaker wires of my CA A1 while debugging why there was no audio (no audio playing while I unlpugged) the sparks really flew. One of the transistors literally exploded.

 

[Anonymous]

I will try all those things, and see where I get.

ÿ

What I have done in the mean time, and god knows if it is ok, is to push in the b selector button for the speakers, and am running both off the left channel. ÿOne on the a side terminals and the other (obviously) on the b side of terminals.

ÿ

I am guessing this won't harm the speakers etc, but just won't give me stereo sound, as both speakers are being driven by the same channel. ÿIs this safe to do, and does it actually screw the sound up?ÿ

 

[Anonymous]

seduct10n:
I will try all those things, and see where I get.

ÿ

What I have done in the mean time, and god knows if it is ok, is to push in the b selector button for the speakers, and am running both off the left channel. ÿOne on the a side terminals and the other (obviously) on the b side of terminals.

ÿ

I am guessing this won't harm the speakers etc, but just won't give me stereo sound, as both speakers are being driven by the same channel. ÿIs this safe to do, and does it actually screw the sound up?ÿ

TURN IT OFF!!! An amplifier cannot cope with zero impedence, after a while it will shut-down under the safety protector - if the amp doesn't have one (although I think it does) it will eventually blow the transistors and/or some capacitors. Don't do it, get the amplifier repaired as soon as you can.

 

[Messiah]

I gather both speakers are being run off the left channel (that is working) using the A and B terminals. Why is this an issue??

(Not being funny I genuinely don't understand the problem with this)

 

[Anonymous]

Messiah:
I gather both speakers are being run off the left channel (that is working) using the A and B terminals. Why is this an issue??

(Not being funny I genuinely don't understand the problem with this)

Because the right channel will be outputting and yet have no load put on it.

 

[Messiah]

Cheers Hughes!

What if the balance (if it has one) is adjusted to play just the left channel??

 

[Tony_R]

Hughes123:Messiah:
I gather both speakers are being run off the left channel (that is working) using the A and B terminals. Why is this an issue??

(Not being funny I genuinely don't understand the problem with this)

Because the right channel will be outputting and yet have no load put on it.

I don't know of a transistor amplifier that isn't happy running into no load - e.g. open circuit.

Valves aren't happy running into no load but transistors are absolutely fine.

This Cambridge amp will most likely have Sanken (SAP 15 or similar) modules (they look like power transistors but have more legs - 5 IIRC) in the output stages (I have repaired the odd one for friends) and they have fusible resistors as a failsafe in the event of output device failure. I suspect the offending amp has one blown channel, and this will simply be shutdown because the bias has been removed from the faulty output stage.

If there is any significant heat being generated whilst the amp is 'idling' i.e. not playing music, then I would suggest switching it off and getting it repaired!

Tony.

 

[Tony_R]

I rather sadly went in search of an image of the offending part - I'm not certain if the 640v2 uses the same part but this is what I suspect is inside. Most likely a newer part number though...

There are two per channel - a SAP15P and SAP16N

 

[HDNumpty]

I had a similar problem with my v1, one of the front channels went, was repaired, went again...I complained loudly enough and they traded in my 3yr old v1 for a brand new v2, which has been perfect!!

 

[Anonymous]

Gents,

ÿ

Thanks for all your help on this. ÿI popped the lid off it and took out the 4 off fuses on the output stage. ÿI put them back in in a different order, and low and behold, the amp now works again!

ÿ

I have not got a clue as to why this happened and why, but being a mechanical engineer, electrics is not my strong point.

ÿ

Thanks for all you replies, merry xmas to all of you, as I am off to listen to music and get ******!!ÿ