pcb backtracing? - Page 1
Forum section: electronics / beginners

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 02:25:11 pm
content: hello there i have really weird audio amp witch in my understanding is dual or something... here is the thing i wanna power some speakers with it but i cant propertly backtrace it what do i do?lookproblem is there is ic that is sinked with small steel plate as you can see and almost all input traces goes to it. yet i dont now what ic is it because its covered with heatsink how do i find out witch is input and everything else?

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 03:25:38 pm
content: Have you tried taking the heatsink off?

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 03:28:59 pm
content: i did after all those pictures but its so hard to desolider it jeezzedit:my iron seems to have too low thermal capacitance

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 03:35:30 pm
content: You might have to add a teensy bit of solder to get it to flow and a solder sucker would really help. Maybe someone will know what it is if you tell us where you got it or what it is or something?

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 03:46:56 pm
content: it has tda1519c in itits from computer speakers its an audio amp from old kinyo driver. google doesnt seem to know more than nothing about board but there is one really weird thing it has tl072cn dual opamp and its 1 and 2 legs are bridgedhttp://pdf1.alldatasheet.com/datasheet-pdf/view/159243/STMICROELECTRONICS/TL072CN.htmlthis is data sheet for it and it looks odd to meghetto solution? heat up solider with small torch bassed lighter?

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 03:49:25 pm
content: Pins 1 and 2 on the opamp being connected means they're probably just using it as a unity gain buffer. Unless you mean solder bridged, as in accidentally.

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 03:52:56 pm
content: i only have basic idea of electronics im a noob but im willing to learn itit has intentionally bridged pins one and two and its also that connection is connected to the 3rd pin witch is broke with big ass ceramic cap

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 03:59:46 pm
content: Quote from: katzohki on March 05, 2015, 03:49:25 pmi didnt quite understood what its for but im guessing its like resistor with isolation from backfeeding?

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 04:02:25 pm
content: btw my iron seems to cool off to temperature it doesnt melt solider it just heat that sink up and im affraid its gonna end up bad for that ic and that lighter doesnt really help what should i do? and yes i bought that thing that sucks tin

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 04:03:59 pm
content: It's going to be a bit hard to figure out exactly what you have going on without being able to see the full circuit, but one clue is that the big chip on thesideof the heatsink is probably going to be a power amplifier, so look at that one first.I don't know about your iron.

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 04:07:25 pm
content: yea that ic on aluminium sink is tda1519c as i said but its freakin pain in the ass to get that sink off with breaking something during the removali really need to keep that pcb working until im gonna manually route dual tda1554 amp... im just lost...

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 04:20:20 pm
content: Oh ok, looks like that IC is probably the work horse of the circuit:

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 04:24:35 pm
content: you gave me an awesome idea but i dont know if its gonna work. i could simply aboid everything and connect it to tda imput but that low pass filter would be cool. oh and btw i just realised that there is two 8 pinners under that dam sink witch i previusly thought was a single icalso its so odd because as i suspect this pcb drive two 3w speakers with those ICs unders the sink and main tda drive a sub witch happens to be 15w on the original setup

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 04:33:12 pm
content: Quote from: katzohki on March 05, 2015, 04:20:20 pmim wonderring can you tell something about those wires maby they are typical color in industrial standarts or somethingone thing what was definetly there is input and pot to controll volume im not sure about bass controll tho

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 05:02:44 pm
content: Not much you can tell from the wire colors really and the labels are not much more illuminating ("con1" gee thanks). Yeah you could make your own amplifier based on that chip. If you need LPF you can make simple RC one.

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 05:31:35 pm
content: yea but as im checking this ic tda 1519c it doesnt work speaker is mute i made sure 8 pin isnt connected to anything and still dead silent. i was touching input throw a cap

author: katzohki
author_rank: Frequent Contributor
timestamp: March 05, 2015, 06:46:50 pm
content: You need to give it an actual input signal. I think if you keep trying you'll get somewhere with it.Edit:Mute/standby switchVsw(on) switch-on voltage level 8.5 ? ? VVmute mute voltage level 3.3 ? 6.4 VVstb standby voltage level 0 ? 2 V

author: justin66
author_rank: Regular Contributor
timestamp: March 05, 2015, 08:36:48 pm
content: yea and it seems i cursed with amps not working so i took out the chip nicely with sucking in tin but that chip happened to be not working so oddediti was puting (as well as leaving it disconnected) direct 12v on that 8th pin and nothing, dead silent speaker could it be that higher voltage doesnt trigger internal on switch?