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amp repairable??

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mad4mp3z View Drop Down
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    Posted: 11 March 2009 at 3:27pm
hi all, looking for some advice, first of all i know soldering realy good and i also know i need to use a multi meter in ohms mode, i learned a little off my dad (electronic engeneer) before he moved away, now the problem i have an amp here (blaupunkt gta 280) i lend it 2 a m8 n he blew it, it go's onto protect as soon as power is put to the amp now i have been told that its the amp chips but am not 2 sure what one's, iv had the amp apart and there was a few dry joints so i re soldered them and retryed the amp, still going into protect.... i also noticed that 3 of the chips get so hot they cant be touched but the 4th on beside them remaind cold (seen bellow)


im hoping that replacing the chip's will help just looking for a second opinion realy and also any tips or advice other than "throw it away" as i intend on putting it in my girlfriends car to power her 6x9's as the standard head units output is bad

any info will be muchly appreciated and if it must b chucked well so be it, worth a try anyway :D
Shaun
:D


Edited by mad4mp3z - 11 March 2009 at 3:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dannyavila Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 1:58am

Hello Shaun.

I think the problem is in the Output area, specifically related to those power output devices. From here, the amp looks as the "standard" Class AB 2 channel design. By first, those transistors you pointed in a circle are the Mosfets of the Power supply and they switch on and off the main 12 Vdc from battery to the main round transformer (toroidal) to produce 2 symmetrical voltages used to feed the amp section, formed by 1 positive and 1 negative power output transistor per channel. So, if the 4th keeps cool during operation, it's not switching along with the other Mosfets and it could be caused by false contact with the board traces or it is damaged.

Using your 260 multimeter in Ohm scale, try measuring between the legs of the TIP35C and TIP36C transistor (the big ones) which are the power output devices; there shouldn't get any reading close to zero (0) on any of these devices. For accurate readings, remove at least two legs of these transistors from the board and test them as directed before. These devices are connected directly to the speakers terminal posts and are susceptible to get damaged if a short circuit or overload conditions appears on the speaker side. So, if you find a reading close to a short circuit meter probes, you should replace it with the same part.
 
Regards,
 


Edited by dannyavila - 12 March 2009 at 1:59am
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mad4mp3z View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mad4mp3z Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 2:18am
so basicly set my multimeter to 200 ohms remove the chip that stay's cool and see if it reads short (0 or neer that) by testing the 2 outside legs if so replace the part,

thanks for the reply
Shaun
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dannyavila Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 3:21am
Nope. Just check if it has broken solder spots in its legs. Remove and measure the amplifier stage transistors labeled TIP35C and TIP36C. One of them could be in short-circuit and causes an over-current condition to the power supply's Mosfets and got overheated.
 
Cheers!


Edited by dannyavila - 12 March 2009 at 3:22am
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mad4mp3z View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mad4mp3z Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 8:59am
right cool thx, got ya, was half asleap when i read that last night :D:D il have a wee look later on today after college and il let you know

thanks again

p.s.need new battery's 4 multimeter wen i put it to the chips the screen fades 2 nothing lol ahwell



Edited by mad4mp3z - 12 March 2009 at 9:02am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mad4mp3z Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 9:48am
just desided 2 b l8 2 college 2day lol i got all the big chips out and measured them and the ones circled read 007 so guessing short,



to get the reading tho i had to measure the middle and left leg's , the chips on the other side give a "1" reading no matter what combonation i try get a reading  also do i check the mosfet chips in the same way?? may as well make sure they are all fine and working wile im at it :D thanks for the help
shaun


Edited by mad4mp3z - 12 March 2009 at 9:49am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jake_Fielder Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 10:15am

that 1 reading means its out of range for the multimeter, it means the figure is too high for the screen to display, try upping the range from say 200r to 2kr or whatever....

 
If your multimeter is autoranging it means the figure is probably over 20mr (or 20,000,000r) or open circuit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mad4mp3z Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 11:43am
cheers dude il up the setting
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mad4mp3z View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mad4mp3z Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 4:12pm
also can any1 send me in the right direction for getting replacements..

i sourced this page but dont know which one im going for , advice on the best one of the 3 would be good (im guessing it is the top one going by looks)
http://uk.farnell.com/jsp/search/browse.jsp?N=500006+1000052&Ntk=gensearch_001&Ntt=TIP36c&Ntx=

thx peeps :D
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dannyavila Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 7:14pm
Hi Shaun.
 
This seems to be the NPN part you need to replace in your amp.
 
 
And this, the complementary part (PNP):
 
 
Zort!


Edited by dannyavila - 12 March 2009 at 7:15pm
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mad4mp3z View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mad4mp3z Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2009 at 9:40pm
sweet dude, thanks for all your help i will post a wee reply up when i get the parts and fit em to let you know if it worked or not :D:D thanks again
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sc6lou Quote  Post ReplyReply Direct Link To This Post Posted: 02 November 2017 at 1:57pm
Could I get the transistor part number on the two transistor to the left of where you circled them and the two transistors directly across from them.

I believe they are Q209, Q210 and Q309 and Q310.

thanks a would really appreciate it as my son took mine out to repair and did not write the part number to the transistor. 

Regards Leo
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