TDA 7296 (4 nos.) Based AMP Repair - Page 1
Forum section: electronics / repair

author: Mattheprofessional
author_rank: Contributor
timestamp: November 05, 2017, 01:33:58 pm
content: I was trying to repair my 2.1 speaker (Logitech z2300). The issue with the speaker is that the Right channel is not working at all (not even a hum).Any suggestion for the repair , what might be wrong. Its not the control pod that is sure. The fault is with the AMP circuit inside the SUB-WOOFERThe speaker is having a powet of 200W RMSIt has 4 TD7296 , Two bridged for the subwoofer (120 RMS) and one of each satellite speakers (40 + 40 RMS )NEED HELP !!!http://cloud.tapatalk.com/s/59ff132a7d600/en.CD00000198.pdfSent from my Redmi 4A using Tapatalk

author: Mattheprofessional
author_rank: Contributor
timestamp: November 05, 2017, 01:47:33 pm
content: One correctionIts 2 × TDA7296 bridged for the subwoofer nd two TDA 7295 for the left nd right satellite speakersSent from my Redmi 4A using Tapatalk

author: Mattheprofessional
author_rank: Contributor
timestamp: November 06, 2017, 07:26:56 am
content: Help me pls !Sent from my Redmi 4A using Tapatalk

author: SMdude
author_rank: Frequent Contributor
timestamp: November 06, 2017, 08:51:19 am
content: Check the resistance of the subwoofer.Trace the speaker back to amp.Check for power at the amplifier ic's. Find it on the datasheet.

author: Mattheprofessional
author_rank: Contributor
timestamp: November 06, 2017, 10:39:31 am
content: Quote from: SMdude on November 06, 2017, 08:51:19 amI did the same... The amp IC power is good ... havent seen any shot on the IC that is responsible for the right channel speaker. I didnt found any protection fuse for the right channel speaker (none of them have one ) . I am really stuckSent from my Redmi 4A using Tapatalk

author: SMdude
author_rank: Frequent Contributor
timestamp: November 06, 2017, 12:48:54 pm
content: Have you tried connecting another speaker to that channel of the amp?Is there a shutdown pin on the amplifier ic? is it powered correctly?If the speaker is good and you have power at the ic and you have input signal to the amp ic, and the speaker is connected right up to the amp ic, then it is most likely the IC.However, if the input to the amp was shorted to gnd, you might not hear a hum.You *might* be able to check the input to the amp with some headphones, your finger, scope, disconnect input to right amp and swap to left amp.

author: Mattheprofessional
author_rank: Contributor
timestamp: November 06, 2017, 12:59:19 pm
content: Quote from: SMdude on November 06, 2017, 12:48:54 pmI tried hooking another pair of working speaker to the out but no diff. Ita a multi layer PCB tracking of pins are very difficult ...i didnt undestand the circuit itslf... Apart frm the TDA7296 , TDA 7295 there are five 4565 opamps... Is there any way to get the schematics of the board that you know??Sent from my Redmi 4A using Tapatalk

author: SMdude
author_rank: Frequent Contributor
timestamp: November 06, 2017, 01:29:42 pm
content: Try google, you might get lucky.Other than that, look up the datasheets for the ic's, see what are inputs and what are outputs.Even though it is multilayer if you know what pins are the outputs of the 4565 and trace them to the inputs of the power amps, all connections of a multilayer board are still on the surface layers.Just use a multimeter and check for continuity to help you trace.And if you want to get fancy, use a circuit board design program such as diptrace and reverse engineer it. It isn't covered in white paint and the part numbers are intact

author: Mattheprofessional
author_rank: Contributor
timestamp: November 06, 2017, 01:35:50 pm
content: Quote from: SMdude on November 06, 2017, 01:29:42 pmNo luck with google....my reference was the typical application circuit given in the datasheet. Diptrace , i d t know much about it how it works ., HelpsSent from my Redmi 4A using Tapatalk

author: keymaster
author_rank: Regular Contributor
timestamp: November 06, 2017, 11:13:22 pm
content: switch the ic of the right to the left channel and vise versa . 8 out of 10 times an all in one ic amp (like the tda7295) is the problem.

author: Mattheprofessional
author_rank: Contributor
timestamp: November 07, 2017, 03:33:01 am
content: Quote from: keymaster on November 06, 2017, 11:13:22 pmIs there any way to check the IC health without powering up .. Like impedence check ??Sent from my Redmi 4A using Tapatalk

author: keymaster
author_rank: Regular Contributor
timestamp: November 08, 2017, 09:05:01 pm
content: Quote from: Mattheprofessional on November 07, 2017, 03:33:01 amYou can check for dead shorts ,with the multimeter in diode mode .But that is not the only way the ic may fail .

author: Mattheprofessional
author_rank: Contributor
timestamp: November 09, 2017, 06:39:47 pm
content: Quote from: keymaster on November 08, 2017, 09:05:01 pmI tried that already on supply in pins... But i didnt fimd any shorts thereSent from my Redmi 4A using Tapatalk

author: Bashstreet
author_rank: Frequent Contributor
timestamp: November 09, 2017, 07:38:09 pm
content: Ok this is what i have experienced myself.1. Symptoms one channel in amp works just fine ... Another is dead.It can be many things but for me it turned out to be shorted disk capacitor in the output (Got shorted when i dropped lead .. that hit pc case.. and grounded..As for you not bad idea still check the caps for shorted ones.

author: Mattheprofessional
author_rank: Contributor
timestamp: November 10, 2017, 03:23:12 am
content: Quote from: Bashstreet on November 09, 2017, 07:38:09 pmOnly disk caps or all caps???Sent from my Redmi 4A using Tapatalk

author: SMdude
author_rank: Frequent Contributor
timestamp: November 10, 2017, 06:59:07 am
content: I notice there are 4 jumper wires going to each amp IC.Can you check if these go to the amp inputs?If they do, it is an easy case of cut them and jumper the signal to a working amp and confirm if there is input signal to the non working amp.

author: Mattheprofessional
author_rank: Contributor
timestamp: November 19, 2017, 10:31:00 am
content: Quote from: SMdude on November 10, 2017, 06:59:07 amThanks fr the headsup..ill check nd tell youSent from my Redmi 4A using Tapatalk