ic audio chip problem help *FIXED*

[jacko1970s]

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.

thanks
jason

[kjr18]

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)

[jacko1970s]

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 on

thanks
jason

[Refrigerator]

Most likely a clone of the LM4871.

[tunk]

Could the original problem be a bad headphone socket?

[jacko1970s]

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 sound

jason

[jacko1970s]

these are the voltage when headphones are plugged in on the 8005 chip and when headphones not connected pic attached

[Refrigerator]

these are the voltage when headphones are plugged in on the 8005 chip and when headphones not connected pic attached

Voltages don't really mean anything, it's better to draw a schematic of how the IC is connected.

[jacko1970s]

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 one

thanks
jason

[jacko1970s]

hi bought chip you said i might be a clone of but no joy but speaker does make a quiet hum

[jacko1970s]

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

[jacko1970s]

now moved topic to repair to try to get more help

[tooki]

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.html
https://www.aliexpress.com/item/4001153633156.html

Most likely a clone of the LM4871.

Distantly, 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.

[jacko1970s]

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

[tooki]

Thanks for taking the time to let us know it worked! Glad you were able to get it up and running again.