Problem with MyRef Rev C based on LM3886 - Page 3

AndrewT · 18th January 2012, 04:55 PM

PINs 9 & 10 are the +IN and -IN inputs.

All opamps should have almost identical voltages on these two PINs.
Something is seriously wrong.

vishnupg · 29th May 2012, 02:34 PM

hi,
hamand do one thing, first of you remove lm318 from the slot,
then power on the board and ensure that you have -35 volts and +35 volts on those two big capacitors.you must keep negative terminal of multimeter on ground in the pcb(the common track for those caps is the ground) while measuring this. if you have the voltage ok there then your power section is ok.

then measure the voltage at pins 1,5,4 with respect two ground. 1 and 5 must have +35 volts and 4 must have -35 volts.

let us see the outputs

vinodt1347 · 1st July 2012, 02:50 PM

Hi,
The LM3886 chip shows very low voltages at Vin+ and Vin-. Obviously something is very wrong. Would suggest you remove all the semiconductors and check the rectifier side to see if you get aprox 1.4 x Vac at the filter caps. Check to see if there are any shorts and component values placed for Resitors and Caps. If this step fails you may need to reconstruct the board. I did purchase this from Siva and it worked first time.
BTW I am impressed with your Enclosure and transformer? Where did you source these?

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18th January 2012, 04:55 PM	#21
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	PINs 9 & 10 are the +IN and -IN inputs. All opamps should have almost identical voltages on these two PINs. Something is seriously wrong.

29th May 2012, 02:34 PM	#22
vishnupg diyAudio Member Join Date: Jan 2010	hi, hamand do one thing, first of you remove lm318 from the slot, then power on the board and ensure that you have -35 volts and +35 volts on those two big capacitors.you must keep negative terminal of multimeter on ground in the pcb(the common track for those caps is the ground) while measuring this. if you have the voltage ok there then your power section is ok. then measure the voltage at pins 1,5,4 with respect two ground. 1 and 5 must have +35 volts and 4 must have -35 volts. let us see the outputs

1st July 2012, 02:50 PM	#23
vinodt1347 diyAudio Member Join Date: Aug 2010	Hi, The LM3886 chip shows very low voltages at Vin+ and Vin-. Obviously something is very wrong. Would suggest you remove all the semiconductors and check the rectifier side to see if you get aprox 1.4 x Vac at the filter caps. Check to see if there are any shorts and component values placed for Resitors and Caps. If this step fails you may need to reconstruct the board. I did purchase this from Siva and it worked first time. BTW I am impressed with your Enclosure and transformer? Where did you source these?