Arcam Alpha 5 no output - help

AndrewGM

Member
2008-06-12 4:18 pm
Hi

My Alpha 5 is working, disc spinning, display and functions are OK but there is no sound.
The 4 regulators on the DAC board are cold, The SAA 7220 is hot.
Regulators on the mono board are hot.
It all seems normal.
I've lifted and re fitted the DAC board several times and still it's quiet.

No caps leaking, resistors burnt, no bangs as is often the case when I muck around with things.

Any tests or suggestions welcome.

Thanks

Andrew
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Buzz the opamp inputs with a metal screwdriver for a quick easy test... keep the volume down on the amp. Is there any buzz or noise or not ?

Supplies OK to opamps ?

Muting OK, not on ?

Post a circuit and we'll have a look :)
 

AndrewGM

Member
2008-06-12 4:18 pm
Mooly thanks

Do you mean literally ' poke ' the opamp legs with a screwdriver and listen for buzz ?

I also wouldn't know about the muting !
Where is that ? ( I hope it's not too obvious )

By the way, I forgot to mention....I recently transplanted the whole of the mono board and attached transport to another Alpha 5 case.....carefully of course and had no accidents along the way. The new case is much cleaner
and... damped - hence the motive for doing it.
Have I done something simple perhaps ?

Thanks for your suggestions

Andrew
 

AndrewGM

Member
2008-06-12 4:18 pm
Mooly Hi

Changed mono boards and it's back - all fine.

I must have damaged something on the original board.
So I fixed it but once again I don't know what or how.
I need to look at the board closely to see if there's anything obvious.

But hey, thanks for being there !
Regards

Andrew
 
Best thing to do in a case like this is to have a methodical look at the board with a 'scope. Something like:

- Are the power supply rails all present and correct?
- Does the digital bus into the SAA7220 look good?
- Does the digital bus from the SAA7220 into the TDA1541A look good?
- Does the analog output from the TDA1541A look good?
- Does the analog output from each OP27 look good?
- Does the analog output from each NE5534 look good?

The fact that both channels are not working makes me suspect that you won't get past item four. Once you've figured out which item above is the problem, it should be fairly straightforward to fix.