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WAS: Fried a Legato? No, no, no
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ipa4me  
#1 Posted : Friday, June 22, 2012 3:41:30 AM(UTC)
ipa4me

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UPDATE : there was nothing whatsoever wrong with any of the TP
parts I built. I somehow got I2C 'control' data lines mixed up with
I2S 'signal' data, and decided early on that all my dual-mono setup
needed for both channels was input sourced to the left DAC.

I still can't quite figure out how I made this gross mix-up but my advice
is to read the integration guide 3x after the 2nd time, if not 4x. Whistle

I just got the parts in to build new ribbon cable and I assure you, when
you connect both DACs beautiful stereo or multi-channel music is possible.
Thanks again to Leonvb and Amaro (who first flagged my obvious
issue) over on this thread:

http://www.twistedpearaudio.com/forum/yaf_postst2596_Dual-mono-ADC-volume-pot-connector.aspx

Thanks again everyone!!! Russ, Brian - what fantastic design and
support. I just decided my older traditional CD collection just easily
doubled in value, if not tripled!

Thanks again TP.
----------------------------------- original post ------------------------------------------------------------------

Another bonehead move. I plugged in a new Legato 3.1 for checkout
and didn't have IC-1 in it's socket. Swell, go draw another ipa in the
basement. I powered it up and now it draws down both +/- rails of my
Placid BP from ~14.6 V to around 7 volts on one side and only about
3.5 on the other. I can't find any obvious bad parts like resistors or
caps. And I reflowed most everything on the board just to double check.
It looks identical to my other board that works and zeroed out perfectly.

I'm afraid to swap IC-1 in figuring I did some other damage to the problem
board.

bottom line:

Did I fry my legato with no IC-1 in the socket?

/Mike Brick wall

Edited by user Tuesday, July 10, 2012 12:23:37 AM(UTC)  | Reason: edited to add solution
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ipa4me  
#2 Posted : Friday, June 22, 2012 9:52:00 PM(UTC)
ipa4me

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Update:

After measuring and more re-flowing and double checking
for missplaced parts, etc. the board finally started working.

The relay wasn't pulling in at power up, but after a minute or
2 it pulls in (sometimes). I've checked the coil on it and it
seems to match the data sheet (~5.3kR). Can't find any other
sources of high R to cause problems. I think I'm going to swap
out that relay.

/Mike
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ipa4me  
#3 Posted : Monday, June 25, 2012 6:36:02 PM(UTC)
ipa4me

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The board I was worried about seems OK, but it's voltage
is only 7-8 vdc on one rail at start up, and only around 4.5-5 v.
on the other. Both sides slowly rise until after ~ a minute they
are high enough to pull the relay in, then bingo! normal V on
both the +/- rails.

Is this indicative of a bad or poorly soldered capacitor? Dang
I've re-flowed everything. Maybe I got something too hot for too
long?

Seems ok after the relay pulls in.

/Mike
d'oh!
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Russ White  
#4 Posted : Tuesday, June 26, 2012 12:22:34 AM(UTC)
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Are you getting good AC voltage into your VREGs from the transformers?
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ipa4me  
#5 Posted : Tuesday, June 26, 2012 1:51:11 AM(UTC)
ipa4me

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Yes, Russ. The output on the Placid HD BP matches the Legato, slowly rising until the relay pulls after maybe 45 sec.
Then everything comes up to my ~14.75 settings. Comes right up when the relay makes. Maybe I am looking
at the wrong end maybe I need to recheck the Placid HD BP. I did have to redo some missplaced transistors on
one of these.

Looks fine after the VDC comes up enough to let the relay pull and all adjustments are normal at that point for I anc V out.

I'm just finishing hooking everything up and will final test tomorrow I hope. Thanks for your reply and help, Russ.

/Mike
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avr300  
#6 Posted : Tuesday, June 26, 2012 4:51:23 PM(UTC)
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The rails shouldn't raise slowly. It should be more or less instantly. A matter of mS.

How's current setting on the Placid ? Are you shunting enough ?
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ipa4me  
#7 Posted : Tuesday, June 26, 2012 6:07:12 PM(UTC)
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I out looks to be ~361mA with ~106mA shunted on
both rails, just below 15 VDC cold. Should I adjust for
more I out? I was shooting for ~365mA.

BTW on cold start I just timed it and it took the one
'cold' Legator 1 min 21 sec. before the V rose enough
to pull the relay. Then I measured the values above.

So the board is basically cold. Should end up ~14.6-14.7 warmed
up.

Thanks for suggestions, etc.

/Mike
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avr300  
#8 Posted : Tuesday, June 26, 2012 6:20:33 PM(UTC)
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One to rule out the Legato.

Try to load the Pladic with two resistors, 1 from + to gnd and 1 from gnd to -

Then measure across those two resistors. Are the rails still raising slowly ?
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ipa4me  
#9 Posted : Tuesday, June 26, 2012 7:11:57 PM(UTC)
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I could try it agian before the relay pulls and all goes to 'normal'.

I'm going to fire it all up first with the buffalos stacked and hooked up.
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avr300  
#10 Posted : Tuesday, June 26, 2012 7:17:07 PM(UTC)
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To clarify:

One to rule out the Legato.

Try to load the Pladic with two resistors, 1 from + to gnd and 1 from gnd to - , with the Legato disconnected.

Then measure across those two resistors. Are the rails still raising slowly ?

Edited by user Tuesday, June 26, 2012 7:17:57 PM(UTC)  | Reason: Not specified
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Russ White  
#11 Posted : Tuesday, June 26, 2012 11:33:44 PM(UTC)
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Thanks for pitching in avr300. Much appreciated. :)
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ipa4me  
#12 Posted : Wednesday, June 27, 2012 2:15:35 PM(UTC)
ipa4me

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Thanks AVR300,

When I swap the Legato to another Placid BP the voltage does the same
thing at start up. My other legato is 'normal' - full voltage at start up
as it should be - with either power supply.

The REALLY ironic part about this is the 'slow' Legato is on my LEFT
channel with dual-mono it is the 'control' DAC with firmware in place.

The Right channel DAC with the Legato that was never in question
is the channel I get no audio out as of 'so far'. The left channel with
the 'slow' legato plays beautiful music.

I'll sort it out - I think it's another configuration issue maybe.

/Mike
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avr300  
#13 Posted : Wednesday, June 27, 2012 8:13:12 PM(UTC)
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Originally Posted by: Russ White Go to Quoted Post
Thanks for pitching in avr300. Much appreciated. :)


No problem, we are here to help. And you 2 guys can be all over the place.
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avr300  
#14 Posted : Wednesday, June 27, 2012 8:15:16 PM(UTC)
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Originally Posted by: ipa4me Go to Quoted Post
Thanks AVR300,

When I swap the Legato to another Placid BP the voltage does the same
thing at start up. My other legato is 'normal' - full voltage at start up
as it should be - with either power supply.

The REALLY ironic part about this is the 'slow' Legato is on my LEFT
channel with dual-mono it is the 'control' DAC with firmware in place.

The Right channel DAC with the Legato that was never in question
is the channel I get no audio out as of 'so far'. The left channel with
the 'slow' legato plays beautiful music.

I'll sort it out - I think it's another configuration issue maybe.

/Mike


Can you post a good sharp picture of the faulty legato ?
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