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Just completed the Buffalo with Legato 1.0.3 running SE. However, there's no sound. I'm getting a short across SE out when power is both on and off - so this may be the problem (there is no short on balanced out). I'm running 3 x trannies in with 12.3V on all inputs. I've Adjusted VR1 and VR2 to 1.7V at Buff input. Tested the Buffalo board in a friend's rig - no problem here. Any suggestions would be appreciated. narla attached the following image(s):  Legato pcb 3.JPG (243kb) downloaded 364 time(s).You cannot view/download attachments. Try to login or register.
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Check the relay. Especially orientation.
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Please forgive the intrusion, but I've been trying to help narla remotely (he's in Australia, I'm in UK). I don't have a legato, but have been looking at simple fault finding..  Seems to show that the relay is OK. Solder connections appear OK. With power to the board, he has short to ground on pin 4 of the relay, but not on pin 5. He also has no output when you use r+/gnd and l+/gnd, for simple SE output.
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Joined: 11/3/2010(UTC) Posts: 169  Location: Quebec
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Sorry, I'd love to help but I have more of a question... Those red resistors, are they RA? If yes, where did you buy them?
Thanks
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Is there a "click" from the relay when the board is powered?
Sure is a shame that it is not working with all those costly Z-foils and discrete opamp......
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My suspicions still lie with the relay. You can actually run the cct without a relay to test. Just turn off your amp before you turn of the Legato.
It could be that it got overheated during soldering which can cause it to hang open or closed.
You also may need double check the opamp.
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Rank: Member
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Thanks for all comments - greatly appreciated. I do get a click from the switch when power is applied - however, it may be best to extract the switch and test. Do I need a link between pins to do this?
Regarding the resistors - they're PRP.
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No you don't need a jumper when removing the relay. It's purpose is to short the outputs to GND when the power is removed to ensure there is no turn off thump.
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Hi Russ - switch now removed, but still getting a short on SE outs. Does this point to the discreet opamp?
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Looks to me like your jumpers on the ommitted output buffer transistors are incorrect? Russ, can you confirm for him?
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barrows wrote:Looks to me like your jumpers on the ommitted output buffer transistors are incorrect? Russ, can you confirm for him? Nice spotting Barrows. Yes, I hadn't noticed before but they do look like they are incorrect. QN8,10,12,13 have the jumper in the wrong spot. It should be from base to emitter but you have it from collector to emitter.
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Thanks Barrows and Russ - have now put jumpers between emitter and base - however I still get a short across SE outputs. Any ideas greatly appreciated.
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Now I would concentrate on your discrete op amp. First just try removing it, then maybe replace with something like OPA2227 to test.
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Russ - before removing the discreet opamp - is there any value in putting a multimeter across the pins to test?
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with power on are you getting any music? All of the inputs are going to be near 0V. That is normal. Same for the outputs except the AC signal when music is playing.
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Russ - great news - beautiful music! Looks like the jumpers were the problem. Thanks so much for your help.
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narla wrote:Russ - great news - beautiful music! Looks like the jumpers were the problem. Thanks so much for your help. what discrete opamps are those?
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Rank: Member
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Hi gaga - the discreet opamps are from Burson.
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