Arcam Alpha 5 popping/clicking noise - diyAudio
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Old 20th June 2011, 10:29 PM   #1
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Default Arcam Alpha 5 popping/clicking noise

After almost a week of modding an Alpha 5 I've had to de mod it to trace an error I've made somewhere.

What I did : All lytic caps on mainboard changed ( plus additional sm bypass caps added ) all caps to DAC board changed. 7805 to RAM and 7805 to SAA7310 and both regs powered from main cap next to traffo - which I doubled in size to 6800uf.
SAA7220 powered with it's own traffo, rectifier, caps and 7805 ( The SAA7220 has been like this for months so I'm pretty sure it's nothing to do with this mod )
470pf styrene cap on DEM and 10 x 100v - 330 nf caps around the TDA 1541A - MSB with 1 uf cap - as suggested elsewhere on this forum.
Took all loading tray plastics out and I use only the laser unit - had an idea for a wood box with top loading )

After this lot the machine played a few tracks really well ( 3 or 4 ) as I'd hoped and then it clicked and popped it's head off - like an on / off switch was being repeatedly pressed.

I've now removed my regulator mods to RAM and SAA7310 and the rest is the same.
Now, I get to play half a disc ( track 1 to 6 of a 12 track disc ) then the plopping and clicking starts again.

Have I got problems with bit or timing errors through buggering around with bigger than standard 330nf and MSB DAC caps ?
Have I got an electrolytic that's breaking down somewhere or the laser unit doesn't like being out of it's plastic tray ?
It's all I can think of.
The disc speed seems constant, like no noticeable variation and particularly during this ' on off ' sound the actual music is advancing in time audibly which is confirmed by the display.

I've done something it's not happy with - any ideas ?

Andrew
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Old 21st June 2011, 08:07 AM   #2
amc184 is offline amc184  New Zealand
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Given that it doesn't effect the tracking of a disc, yet it sounds like a digital fault, I'd be looking at the frame buffer and digital filter. I'd try seperately changing out these two ICs (the SAA7220 and whatever RAM IC it uses for the frame buffer), and seeing if the problem remains. The problem seems to be heat related (half a CD might be the time it takes for the faulty part to heat up), so alternatively you could try hitting these ICs with freezer spray while the fault is present.

It's also worth checking whether the fault is also present on the digital output, this would confirm that the fault is in the digital side of the player.
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Old 21st June 2011, 08:26 PM   #3
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Many thanks for taking the time to reply...again !

I found the problem but it's not what your expecting.

The disc without the tray and loading gear to support it was very unstable and it could easily be seen from the side view that it was a bit like a warped LP.
I simply put another CD on top of the one to be played placed the puck on top and pressed play..........it worked
I've now made a CD sized platter and fixed the magnetic puck to it.
Placed on top of the disc to be played it makes it almost completely stable. .

Now to re mod it again

and finally........

Thanks to EVERYONE else for all their valuable contributions - most underwhelming as usual
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Old 22nd June 2011, 06:36 AM   #4
amc184 is offline amc184  New Zealand
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Ah, I always do that, thinking electrical but never mechanical. I'm glad you got it sorted.
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Old 22nd June 2011, 11:45 AM   #5
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Thank you.

Once again I have over complicated a problem and ignored
basic stuff - it's not the first time either.
I am not so upset about having to re do it - the sound was becoming quite good so I'm keen to get it back.
I hadn't clocked it nor done the NOS mod either - which I'm determined to do to see how it compares to my now excellent old Alpha - my benchmark.
I have some new buddies on this forum who have pushed me to give NOS a try to see for myself.

The other tweak I picked up from them was the bare laser unit rigidly mounted. It provided a very noticeable improvement which I was not prepared for.
I'm assuming the rigidity has reduced mechanical jitter in some way - if that exists.

Back to it then and hey, hope things are returning to normal in New Zealand
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