Can someone explain this circuit?  - Page 1
Forum section: electronics / repair

author: samvivi7
author_rank: Contributor
timestamp: June 05, 2023, 12:56:27 pm
content: Hi expertscan someone plz explain the following circuit. also, i cannot identify two of the components, might be a fuse.any help is appreciated.Thank you.

author: srb1954
author_rank: Super Contributor
timestamp: June 05, 2023, 05:56:52 pm
content: Quote from: samvivi7 on June 05, 2023, 12:56:27 pmA photo of the actual components would be more useful to help identify them.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 05, 2023, 06:23:14 pm
content: Quote from: srb1954 on June 05, 2023, 05:56:52 pmSeems you did not look at the pdf in the opening post.

author: MathWizard
author_rank: Super Contributor
timestamp: June 05, 2023, 07:11:54 pm
content: So the 2 little black things on a vertical trace on the left ? Do they read low resistance like a fuse or inductor ? I don't think I've ever seen diodes in that form, I think just passives get that form with the big metal end caps.Probably fuse or fusable resistor/ small NTC they thing, or inductors, would be my guess from digital boards and their power rails.Looks like some Vin filtering going to the Vin of the lt8631, the other side with the blocking cap could be sensing that rail's AC, or where's that trace above (between R2 C5) the cap going to ?

author: Niklas
author_rank: Frequent Contributor
timestamp: June 05, 2023, 07:42:10 pm
content: Ferrite beads

author: fzabkar
author_rank: Super Contributor
timestamp: June 06, 2023, 12:30:02 am
content: The left side of the circuit is drawn incorrectly. The capacitor that looks like a DC blocking capacitor is actually wired as a power supply filter. Pin #1 of the IC is Vcc.It appears that the designer has used two caps in series to provide some level of redundancy. The diode is probably there for reverse polarity protection.https://www.analog.com/media/en/technical-documentation/data-sheets/ltc6813-1.pdfhttps://www.analog.com/media/en/technical-documentation/data-sheets/lt8631.pdf

author: samvivi7
author_rank: Contributor
timestamp: June 06, 2023, 03:41:16 pm
content: thanks for the replies, very helpful.why is the left side of the circuit incorrect? is it because of the caps in series vs parallel ??i drew them parallel because the second cap rings to ground.is this not correct ??Again thank you for the help.

author: fzabkar
author_rank: Super Contributor
timestamp: June 06, 2023, 04:59:04 pm
content: I believe R2 goes to pin #1 of LT6813. C5 and C6 are connected in series between R2 and ground.

author: samvivi7
author_rank: Contributor
timestamp: June 06, 2023, 07:38:14 pm
content: you're absolutely correct. sorry i messed upis there anyway i can find the value of the Ferrite beads ??

author: wasedadoc
author_rank: Super Contributor
timestamp: June 06, 2023, 10:58:44 pm
content: Quote from: samvivi7 on June 06, 2023, 07:38:14 pmYou posted in the 'Repair' section so I assume this is something you are repairing. In which case you only need the values if the ferrite beads need replacing. If they read very low resistance it is unlikely they are faulty.

author: samvivi7
author_rank: Contributor
timestamp: June 07, 2023, 12:29:56 am
content: they read 0 ohms.i am trying make this board work with no luck so far.so how do i find a replacement for them ?? plz help.

author: wasedadoc
author_rank: Super Contributor
timestamp: June 07, 2023, 07:37:05 am
content: Quote from: samvivi7 on June 07, 2023, 12:29:56 amRead my post again.They are very low value inductors and should read as close to zero Ohms as a normal multimeter can manage. Extremely unlikely that they are the cause of whatever problem there is with that unstated equipment showing those unstated symptoms.