Arcam Alpha Plus cracking

[AndrewE]

Had this excellent piece of kit from new back and linked to my Cyrus One amp it has served me really well.

I have just added to my system with my wife's old Dual turntable and Marantz tape deck. These all worked fine (after replacing cartridge on Dual and cleaning amps input selectors to get tape deck output working).

BUT now for some inxplicable reason the Alpha Plus has started crackling after it warms up. It starts with a quiet crackling then gets louder until you cannot hear the music, just crackling. I have replaced cables, power supply with no success. I also replaced CDP with a Marantz which plays with no crackles so its not the amp

I am assuming it is one component that has for some reason is failing when getting warm

Can anyone give advice to a beginner how I can locate fault. I read that on the Alpha 5 the same thing happens and its an electrolytic capacitor but the boards are different in the Plus

cheers

[AndrewGM]

Is it a 5 Plus you have ?

The 5 and the 5 plus share the same mainboard and the capacitor C416 is known to fail.
You can see it easily with the lid off and it's at the top right hand side near the back - behind the main transformer. It's a 470 uf 25 volt rubycon and has two transistors, some resistors and diodes around it.
Have look at it and see if there's any gunge leaking out of it or if the resistors look ok.
I'm no engineer but I've had the same problem - replacing all the bits fixed it.

I don't remember the crackling noise however.

Someone clever will jump in soon

Good luck

Andrew

[AndrewE]

Andrew its not a 5 or a 5 Plus - its the Alpha Plus which came out just before the 5

I hasn't got a C416 - the numbers on the main board go up to about C220 or so

[Mooly]

Does this have the Philips "swing arm" laser fitted ?

If so there is a 33uF cap on the PCB under the laser that is a common issue... I'm not sure whether that applies to all variants of the Philips but is a common issue.

This might sound daft but is the lens clean ?

And don't alter any pots for laser power

Crackling can be a sign that the signal picked up from the disc is sub standard. Although we tend to think of CD as all or nothing that is certainly not the case. It is a typical symptom.

Another purely electronic issue can be failing DRAM.

Which was the problem here,
CD player with distortion. laser?

[AndrewE]

Thanks Mooly

I don't know if it has the swing arm laser, but pretty sure its a Philips - how can i check?

Its weird that it has suddenly started after years of constant use, so I can't believe its the lens, although it may be something got there from nudging the player - is there a standard cleaning procedure?

DRAM? sorry not an acronym I am familiar with

Is it worth just replacing the 33uF cap? Is it obvious which one I should replace - will I see something wrong? (haven't got the player open so can't see the board at the mo')

cheers

[AndrewGM]

Apologies.

The mechanism is the 4 / 19 swing arm mech.
I have two original std Alpha's and more recently a plus model.
I know these machines quite well.

Mooly is correct - a 33uf 16v cap exists and is marked as 2532 on the copper surface. Right in between two yellow 220nf film caps.

Get the lid off and then slide by hand the transport tray open.
You should just be able to see the cap to the left of the back transport screw ( which holds the transport mech to the chassis ).
30 mm ish to the left of the screw.

The DRam is the memory and if it's this that's failed then it's going to be a stinker.

Sorry for that bit of news

[AndrewGM]

Also, you may need to unclip the DAC board too.
Unscrew the screws on the back plate which secure the RCA sockets.
Remove the plug which takes the power to the DAC - the cable of which goes to the small transformer to the right.
Then unplug the the other cable - this one is easier to remove.

Pop the plastic plugs which hold the board in place and it should lift away.

[amc184]

This is a slightly unusual problem. There's a few things I can think of that may cause this:

- A bad frame buffer DRAM. I've seen these fail occasionally, which usually results it the player making very loud, harsh noise.
- A bad DAC IC. Sometimes the TDA1541A does fail, and this is how it can manifest itself.
- A faulty solder joint, probably on the output connectors.
- A problem with the output stage or DAC power supply. Nothing functions right without a good power supply.

I'd run through a few checks to localise the problem. Can you try these things out:

- Does the data from the S/P DIF output have the same problem as the analog outputs? Try plugging the CD player's digital (S/P DIF) output into a separate DAC, HT receiver, PC or something else that can convert it to sound.
- Does wiggling the cables to the analog outputs near the connectors effect the problem?

I wouldn't think this problem would be due to bad components in the servo as disc tracking isn't affected. To check it definitely is using a radial armed mech simply eject the tray, it'll have a distinctive arc shaped cutout.

[AndrewE]

Originally Posted by AndrewGM

Apologies.

The mechanism is the 4 / 19 swing arm mech.
I have two original std Alpha's and more recently a plus model.
I know these machines quite well.

Mooly is correct - a 33uf 16v cap exists and is marked as 2532 on the copper surface. Right in between two yellow 220nf film caps.

Get the lid off and then slide by hand the transport tray open.
You should just be able to see the cap to the left of the back transport screw ( which holds the transport mech to the chassis ).
30 mm ish to the left of the screw.

The DRam is the memory and if it's this that's failed then it's going to be a stinker.

Sorry for that bit of news

i have a chance to go into a Maplins today - but no chance to open the CDP

Any more description on the cap would be useful so I can buy one today in advance

ta

[Mooly]

Originally Posted by AndrewE

Thanks Mooly

I don't know if it has the swing arm laser, but pretty sure its a Philips - how can i check?

Its weird that it has suddenly started after years of constant use, so I can't believe its the lens, although it may be something got there from nudging the player - is there a standard cleaning procedure?

DRAM? sorry not an acronym I am familiar with

Is it worth just replacing the 33uF cap? Is it obvious which one I should replace - will I see something wrong? (haven't got the player open so can't see the board at the mo')

cheers

To clean the lens use a pure cotton bud with the cotton teased out slightly.
I have some Sony fluid so never really know what to recommend, but NEVER glass cleaner as it often has ammonia and other chemicals. Isopropyl alchohol always gets recommended, and yet that is the one product Sony told us never to use as it damaged early lenses with coated optics.

I guess camera lens fluid would be OK. If the player is in a smoke free environment then just use a little warm water to moisten (not wet) the bud and very gently wipe the lens.

The cap could be favourite though.

DRAM is dynamic random access memory, bit like todays RAM but from a time when somthing like 32kb or 64kb on a chip was quite something. If that fails then the fault tends to be a "hard fault" meaning that it's present all the time, unchanging. I would doubt thats the issue here if the crackling progessively increases.