NAD 320 BEE - from one to next - Page 1
Forum section: electronics / repair

author: mauric
author_rank: Contributor
timestamp: October 11, 2020, 03:10:20 pm
content: Hello MembersI'am now a Week to work on my NAD 320 BEE amp, a replaced meny Caps, theinstalled was ancient and broken, also the Relay was damaged. Now the ampare the first time up (from his Protect mode), but the defective shafts continues.and now I'm amazed, because I marked a coule day this resistor R068 3W as ok,but now this four pieces are burned, and only this, if messure the otherparticipants in the area around the "railway" this seem to be ok?please iam not a expert ... but I would bet that if I replace these 4 resistors thenext faulty will appair .... please how i can or.. please can somehow preventsuch domino effects like this?The Power are running 48+ and - the Fuse are fine. the initial error was a ampthat don't come out from protect mode.Thanks for discuss thisRegardsMauri

author: coromonadalix
author_rank: Super Contributor
timestamp: October 12, 2020, 02:33:08 pm
content: hifiengine has your service manual, registration is free it will help you

author: mauric
author_rank: Contributor
timestamp: October 12, 2020, 04:17:30 pm
content: Thx, Yes i'am Member since 3 years and 15 weeks ;-)

author: Twoflower
author_rank: Frequent Contributor
timestamp: October 12, 2020, 04:42:06 pm
content: Is the meter actually in Resistor mode? I see a V and probably DC in the display...

author: SpecialK
author_rank: Regular Contributor
timestamp: October 12, 2020, 06:24:50 pm
content: When you say "resistor R068 3W as ok, but now this four pieces are burned " do you mean:1 - R068(not marked on schematic) broke into four pieces2 - All four 0.068 ohm resistors are visibly burned up?3 - All four 0.068 ohm resistors report as dead shorts?4 - All four 0.068 ohm resistors report as open circuit on ohmeter?I don't think you can measure a 0.068 ohm resistor without using a four wire multimeter. Lead resistance would be greater than load resistance.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: October 12, 2020, 08:36:53 pm
content: Quote from: Twoflower on October 12, 2020, 04:42:06 pmyup, seems to be the casealso, those resistors' fault mode is usually "open", but not "shorted"

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: October 12, 2020, 08:39:53 pm
content: Quote from: SpecialK on October 12, 2020, 06:24:50 pmactually, you can. just short the probe wires and take a note of the resistance. then, take your measurement on the R068 and subtract the resistance value that you have noted before.any result greater than zero would tell you that the resistor is most likely ok.

author: mauric
author_rank: Contributor
timestamp: October 13, 2020, 07:36:35 am
content: Thanks for so meny Answer that i receive!!Yes and sorry this was my Mistake!! if running the Multimeter in Resistance-modei have a resistore value from 0.3-0.4OhmI mount everything in the case, Power on, put the Sinus to Chinc, No Sound appair, appair little brum on both speakers.Knocking on the transistors with a hard object, but hum does not change.the Amp are now still running, the temperature it's in my opinion not critical!thanks for possible update or input!

author: mauric
author_rank: Contributor
timestamp: October 14, 2020, 01:45:45 pm
content: I measured the following points earlier. I don't know exactly how to continue here. Please helpStill no sound, and little hum on both Speaker.

author: SpecialK
author_rank: Regular Contributor
timestamp: October 14, 2020, 02:11:19 pm
content: Check R445 and R446 as they are the sense for the protection circuit.Also check D419 and D420 as they seem to be the in the feedback mechanism for the soft-clip circuit.

author: mauric
author_rank: Contributor
timestamp: October 16, 2020, 03:50:54 pm
content: R445 and R446 check, are still OkD419 and D420 check, are still OkSorry still measure..... but seems to ok....Still no sound .....

author: SpecialK
author_rank: Regular Contributor
timestamp: October 16, 2020, 06:45:24 pm
content: Jumpers between pre-out and main-in?