Connect with us

Amp repair

Discussion in 'Power Electronics' started by Roflsandwich, Sep 28, 2019.

Scroll to continue with content
  1. Roflsandwich


    Sep 28, 2019
    Trying fix a broken amp out my car and need identification of parts on board to test them I’ve bought 2 amps already and would like try to repair before I buy another. I know this alot of Id of parts but any input would help as I cant find anything online.

    Toyota 86280-53110

    Pionner GM8157ZT
    Board 1 CWM9580
    Board 2 CWM9581

    I can provide picture as it dissembled I will up load as soon as possible.
    Last edited: Sep 28, 2019
  2. dave9


    Mar 5, 2017
    It might help if you described the symptoms of what it isn't doing.

    Rather than test individual parts, one way to do it is think about how it works. You have power going in which you can trace with a multimeter, and signal coming from an internal source which you can trace to the output.

    While it could be a component like a transistor or amp IC, tracing also shows continuity between two parts in the path in case there is a bad solder joint or PCB crack.

    The trick with car stereos can be having it apart yet still having multiple boards connected together.
  3. Roflsandwich


    Sep 28, 2019
    I have confirmed that it has power coming in and ground is good, this is a weird amp for a 2007 lexus is250 all control from the factory head unit is sent to this amp input/aux cord, volume control, balance, fade, ect and done through 4 wires. It's there proprietary software there is no way to bypass amp as in cut the input wires and connect to high level input on aftermarket. But it is receiving signal from head unit idk what but signal is there. But no output to speakers at on wires at amp also all crossovers and filters are handled in amps dsp board to the speaker wire from amp it like typical system
  4. Roflsandwich


    Sep 28, 2019
    But I did have a smp resister break off I believe, weak solder my guess, it had the markings for 427 on it, took almost 10mins of getting the right to read it without a magnify glass. I will upload pictures with in an hour
  5. Roflsandwich


    Sep 28, 2019
    Red line is where 427 is missing

    Could not upload on this website said error has occurred
  6. davenn

    davenn Moderator

    Sep 5, 2009

    You sure it was 427 and not 472 ? 427 (42 MOhms approx. a monstrous value)

    472, on the other hand, is 4700 Ohms, 4k7 = a very commonly used value

    It's highly unlikely to be a multi Meg Ohm value
  7. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir Roflsandwich . . . . .

    Since that photo seems to be delving within the power amp section of the unit .
    Take note of the L903 toroidal power inductor at the top of the magged up photo and the LARGER E-cap nearby and the probability that these are being associated with the filtering and conversion of a digitally processed audio pulse width signal back into an analog signal to feed to the speakers.

    Located just below the large toroid, there are being a series string of small signal discrete parts, starting with a 4.7K (472) SM resistor near the large E-capacitor. Then it feeds to the right to the base of a SM flat pack transistor beside it to the right.. That transistors collector gets connected to one end of another 4.7K SM resistor. Then, there is the area of your missing resistor and another SM transistor over to the right.
    I would venture an educated guess, that the missing resistor is also being a 4.7K SM resistor, since it would be in circuit across the base to emitter of that last meentioned transistor.

    The collector of that final transistor then passes up to connect to a moderate sized diode . . . . which I can only make out as a D 8? . . .start
    ( BUT . . . .all of the other immediate area parts are receiving " 900" series markings assignments.

    Now with all of this pointing out of circuitry aspects, take a good look all around the board and patricularly for a like toroid (s) in case this unit has more than 2 audio channels.
    I really think that this specific series string circuitry will be identically replicated elsewhere, and you should be able to read the "like" resistor in other circuitry, since what are the odds of another being damaged. PLUS it does take some SERIOUSLY high voltage across it to tickle some 4700 ohms of resistance.

    Now . . . . . CHECKITOUT . . . . . ! ! ! !

    PLUS . . . . . ADDITIONALLY . . . . . like in the Clint Eastwood movie . . . . . . I jes' gots to knoes !

    I am looking at EVERY little area of the foils on this little snippet of a photo, and every where, I am seeing black deposits akin to cockroach deteris, and MORE IMPORTANTLY, the MULTIPLE areas of bared copper foils that are open air exposed.
    Below the large E-cap, board edge, there is also corrosive foil "creep" entering at the edges of the board, going in under its conformal coating.

    Where the HELL has this unit been during the last 13 years of its life ?
    Parked above a toxic envionmental dump . . . . with noxious sulphuric and nitrogen acid fumes wafting thru the air ?
    BUT, if purchased from a junk yard . . . . . with packed dirt surfaces and who knows what fluids being constantly poured into them,
    THAT condition could constitute a hazardous site !

    73's de Edd . . . . .

    Well, I finally POSITIVELY-ABSOLUTELY had to have them replace the metal plate in my head with a Teflon one.
    Every time the wife would rev up the microwave, I'd wet my pants, purge my bowels and also forget where and who I was for about half an hour or so..

    Last edited: Oct 5, 2019


    May 20, 2017
    The standard of soldering in your picture looks horrible. I assume you haven't been messing around with a soldering iron. Also, there seems to be an awful lot of cr*p on the board which won't help. Could be a cart load of dry joints and shorts from rubbish floating around.
  9. Bluejets


    Oct 5, 2014
    From the look of the visible tracks it looks like it been through a "corrosion bath".
    I'd say beating a dead horse trying to "repair" that lot.


    May 20, 2017
    Have to agree with you BJ.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
There are no similar threads yet.
Electronics Point Logo
Continue to site
Quote of the day