ic audio chip problem help *FIXED* - Page 1
Forum section: electronics / repair

author: jacko1970s
author_rank: Contributor
timestamp: June 12, 2020, 03:39:55 pm
content: hi need some help locating a replacement chip that i took off a dab radio but then lost the chip.reason for removal is no sound to speaker but sound to headphone when plugged in. the photo attached are the chip which has 8005 PREaM written on top and second picture is of the location of the chip. yellow circle is the chip location black circle is the speaker plug. note with this chip missing the headphones still play sound.thanksjason

author: kjr18
author_rank: Regular Contributor
timestamp: June 13, 2020, 05:00:35 am
content: Most of the headphone jacks sockets combine contacts for plug and for signal switching. To put it simply: audio signal goes from source to socket, where if there is nothing plugged in, then to amplifier. If there is no audio at the output and there is in headphones then you can be sure that this 8005 PREaM mono power amplifier died. Try to find where pins 1 to 4 are connected, as for quick google search I got TPA721 which might have the same pinout. If you need replacement, try to find chip with the same pinout and close in power (there should be a impedance and power written on a speaker)

author: jacko1970s
author_rank: Contributor
timestamp: June 13, 2020, 12:23:00 pm
content: hi thanks for reply found the chip and put back on the board im still trying to learn and dont really understand what you mean by find where pins 1 to 4 are connected the speaker is 5w 4ohms and pic below are the power values when radio is onthanksjason

author: Refrigerator
author_rank: Super Contributor
timestamp: June 13, 2020, 01:16:09 pm
content: Most likely a clone of the LM4871.

author: tunk
author_rank: Super Contributor
timestamp: June 13, 2020, 09:53:58 pm
content: Could the original problem be a bad headphone socket?

author: jacko1970s
author_rank: Contributor
timestamp: June 13, 2020, 10:12:14 pm
content: im not sure still learning but did do the usual by incerting and removing headphone connector. i removed the headphone socket .there is also no voltage on some of the pins on the pictured ic chip when the headphones are plugged in then the voltage returns when i remove so im guessing the socket is doing what it should.there is also another ic chip on the board LM358 when i removed this the headphones no longer produced soundjason

author: jacko1970s
author_rank: Contributor
timestamp: June 14, 2020, 04:20:41 pm
content: these are the voltage when headphones are plugged in on the 8005 chip and when headphones not connected pic attached

author: Refrigerator
author_rank: Super Contributor
timestamp: June 14, 2020, 08:11:28 pm
content: Quote from: jacko1970s on June 14, 2020, 04:20:41 pmVoltages don't really mean anything, it's better to draw a schematic of how the IC is connected.

author: jacko1970s
author_rank: Contributor
timestamp: June 14, 2020, 08:21:45 pm
content: hi as said only just started learning about this stuff so wouldnt know where to start drawing schemic that would help here is a pic of full board not sure you could point in in the right direction of draw one or explain how to go about doing onethanksjason

author: jacko1970s
author_rank: Contributor
timestamp: June 23, 2020, 03:06:22 pm
content: hi bought chip you said i might be a clone of but no joy but speaker does make a quiet hum

author: jacko1970s
author_rank: Contributor
timestamp: July 13, 2020, 07:38:41 pm
content: didnt get much joy with further help so plodded on update so 8005 chip was one of the problems as bought a 8002 chip pictured and now got sound but very poor quality and distorted and if volume is turned down sound

author: jacko1970s
author_rank: Contributor
timestamp: July 19, 2020, 03:36:19 pm
content: now moved topic to repair to try to get more help

author: tooki
author_rank: Super Contributor
timestamp: July 21, 2020, 06:11:42 pm
content: A quick google search for "8005 amplifier IC" brings up the CSC8005, a little amp IC that looks like it maybe can switch between linear (class AB) and switching (class D) modes. A number of AliExpress vendors have it, e.g.https://www.aliexpress.com/item/4000263639649.htmlhttps://www.aliexpress.com/item/4001153633156.htmlQuote from: Refrigerator on June 13, 2020, 01:16:09 pmDistantly, perhaps. The LM4871 is linear, and seems to have differential inputs. The CSC8005 is almost pin-compatible, but has only single-ended input, and a class AB/D mode selector pin where the other differential audio input pin would be.

author: jacko1970s
author_rank: Contributor
timestamp: August 21, 2020, 01:40:38 pm
content: nice one chip came today took a while fitted works like a dream googled this chip when first took out but thought no chance but thanks to your help working dab radio thankyou

author: tooki
author_rank: Super Contributor
timestamp: August 21, 2020, 03:01:10 pm
content: Thanks for taking the time to let us know it worked! Glad you were able to get it up and running again.