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    How do you test an amplifier?

    Friendlies and not so friendlies,

    Would you fellas happen to know how to test an aftermarket amplifier?

    In the Townie I've got a JBL GTO-5EZ that I think has wet the bed. Things were fine and then one day it started cutting in and out like it was over heating and now I'm not hearing nothing at all. Checked the wiring and nothing was loose. If I turn the stereo all the way up you can still hear the signal through the speakers, it's like the volume is down super low so I assume that's the signal just not being amplified.. Why I think the amp is dead but I'm not really sure how to test it short of putting a new one in it's place which I don't have.

    Any suggestions would be appreciated.

    Cheers,

    Derek
    1985 LTD Crown Victoria - SOLD
    1988 Town Car Signature - Current Party Barge

    #2
    If you have power and ground the only thing left to check is signal. You could ohm out your signal cables to make sure they are complete. You could also hook an alternate source up (phone). And see if you get any response; my money is on a blown amp.


    Sent from my iPhone using Tapatalk
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      #3
      Originally posted by adam.w.ackerman View Post
      ...my money is on a blown amp.


      Sent from my iPhone using Tapatalk
      So is mine, which is why I'd like to verify that with some sort of test before spending moolah on another one. This amp has only been in the car ~3 years and so the way I see it, it still owes me money. Headunit supposedly has 5V preouts, so I could check those but I suspect they're ok since when I turn the stereo to max volume (gain) you can hear whatever is playing very softly through all channels.
      1985 LTD Crown Victoria - SOLD
      1988 Town Car Signature - Current Party Barge

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        #4
        So the amp is driving all your speakers and nothing is powered from the head? If that is the case then I would say your source cables are fine. And the fact you said it was going into protection indicates something failed.


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          #5
          I'd make sure the amp is getting power first and doesn't have a blown fuse. After that, I'd make sure it's getting signal from the head unit and possibly test it with another input source.

          Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
          rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
          Originally posted by gadget73
          ... and it should all work like magic and unicorns and stuff.
          Originally posted by dmccaig
          Overhead, some poor bastards are flying in airplanes.

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            #6
            Thanks sly,

            As for the signal, since I'm hearing stuff out of the speakers isn't it safe to say the amp is getting the signal? I am using the radio's pre outs and feeding them directly to the amp and then the amp feeds the speaks.
            1985 LTD Crown Victoria - SOLD
            1988 Town Car Signature - Current Party Barge

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              #7
              My bet is the amp chips have shat themselves. Seems to be what ails every JBL amp I've had here that didn't work. Confirm power, signal in and speaker out but I expect its internal. Sometimes the fuse blows when this happens, not always. Depends on the particular mode of failure. If it shorts, it will at least try and dump about 40 volts to one of the speakers. This may pop the fuse, but usually it just drags down the power supply so much that the working channels don't seem to do much. Hooking up an ammeter in place of the fuse might tell you something. If its drawing more than about 2 amps with no signal being fed to it, its screwed up.
              86 Lincoln Town Car (Galactica).
              5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

              91 Lincoln Mark VII LSC grandpa spec white and cranberry

              1984 Lincoln Continental TurboDiesel - rolls coal

              Originally posted by phayzer5
              I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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                #8
                Thanks gadget, this is an aftermarket JBL amp- I took Ford/JBL to a whole 'nother level

                First place I should have looked but didn't was the fuse for the line feeding the amp, it wasn't blown but should have been. The whole thing was melted right at the block, glad the cheap shit didn't burn the car down though. With me things are always more complicated than they should be so I just figured it wasn't that and should learn how to troubleshoot an amp. Forgot rule number one; simple things first. So thank you guys for pointing me in that direction. I [briefly] bypassed the fuse and things worked so now I'm off to buy another fuse junction block thing. Can't believe that shit isn't engineered to take high temperatures...
                1985 LTD Crown Victoria - SOLD
                1988 Town Car Signature - Current Party Barge

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                  #9
                  probably modern enough to not have the bullshit parts that you can't get. I think my next step with factory JBL stuff when I run out of spare parts (one more amp) is to buy or build a converter to go from factory wiring to a normal modern aftermarket amp of equivalent power and make up a mounting plate to hang that in the stock location.
                  86 Lincoln Town Car (Galactica).
                  5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                  91 Lincoln Mark VII LSC grandpa spec white and cranberry

                  1984 Lincoln Continental TurboDiesel - rolls coal

                  Originally posted by phayzer5
                  I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                  Comment


                    #10
                    I've got 3-4 factory JBL amps, at least two that are known to be working in good order. So I could probably provide parts if you need them. I hoard that stuff big time, not even sure why..
                    1985 LTD Crown Victoria - SOLD
                    1988 Town Car Signature - Current Party Barge

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                      #11
                      problem is that the old parts seem to have a limited lifespan. I've pulled working amplifier chips out, and they died on re-install. I suspect they had one foot in the grave already and the heat from removing and re-installing was enough to kill them. At some point it just stops being worth the trouble to repair them. Also consider that a lot of people have abandoned the stuff already and it makes for a limited market. I have one spare amp for myself, and parts to rebuild it. If and when the one in the car dies, the spare will go in, and if that dies before the car does I'm probably done with them.
                      86 Lincoln Town Car (Galactica).
                      5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                      91 Lincoln Mark VII LSC grandpa spec white and cranberry

                      1984 Lincoln Continental TurboDiesel - rolls coal

                      Originally posted by phayzer5
                      I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                      Comment


                        #12
                        Hi I know this is a old thread, I used to diagnose, rebuild, repair, car and home electronics ( back when it was worth it to do so )

                        Over the years I have found especially with Car amplifiers and other electronics the main problem would start out as poor solder connections which would cause a intermitant problem with power outputs.
                        If the Amp is continued to be used this way the added heat and resistance would fry the ICs resistors diodes etc in that circuit.

                        Normally repairing them is pretty easy and cheap all you normally need is a DVOM digital volt ohm meter a good soldering iron some delosder wick and if you can find one a capacitor checker that checks for bad caps with the cap still installed on the board.

                        If you want any cheap amplifier to last it is best to take it apart and hand solder each and every connector on the board ( this requires a steady hand good eye sight and a boat load of patience ). I also like to upgrde the heat sink compound while I was doing this type of work.

                        Now that i am much older and have a bad neck and back this type of work is beyond what I am capible of.

                        Anyways I just wanted to le tyou know if you or anyone experiances a intermitant issue with electronics take the item apart use anti static protection mats and straps and closely inspect each solder connection with a large magnifying glass. a clue to where to look may be a dark spot on the board where the added heat and resisitance ha sbeen cooking the bard and parts.

                        If you want or need more tips on how to pin point bad parts at the circuit level I may be able to help but since I do not do this type of work I would have to google some sort of video or wait until I have something worth putting up witht the pain to my neck and back to fix it myself and make a video of me doing it.

                        BTW I am no expert at electronics, anything I know about diagnosis and repairs was taught to me by my brother whom was an expert yet I only learned a fraction of what he had to offer before he passed away. But what i did learn allowed me to diagnose and repair about 80 percent of electronics I tackled the other 20 percent normally was too far gone or had a modern multiple layered printed circuit board and micro parts that was beyond my pay grade.
                        2007 Ford Crown Victoria LX Sport

                        Comment


                          #13
                          Hey man, welcome to the forum and thank you for the tips!

                          I'm at that point now where anything new to me that's old will be done that way. It's more time up front but with my past experience it's time saved down the road because I won't have to pull and troubleshoot the same thing 3 or 5 times... Need the mat, desolder wick and a cap checker first though.
                          1985 LTD Crown Victoria - SOLD
                          1988 Town Car Signature - Current Party Barge

                          Comment


                            #14
                            Originally posted by DerekTheGreat View Post
                            Hey man, welcome to the forum and thank you for the tips!

                            I'm at that point now where anything new to me that's old will be done that way. It's more time up front but with my past experience it's time saved down the road because I won't have to pull and troubleshoot the same thing 3 or 5 times... Need the mat, desolder wick and a cap checker first though.
                            I still have my old cap checker, I have looked online and have yet to find another one for sale, The best best with caps on a amp is to read the value on them and replace them with the same or slightly higher value, but since i do not have my brother to guide me to keep me from buying too high of a value cap for a replacement I suggest just buying the same value caps.

                            So this means you could just buy a good Soldering iron station with replaceble tips and adjustble temprature control ( i like to use a fine point tip )

                            when you buy desoldering wick get do not buy the cheapest you can find I will find the brand that i use and post it. once you get the desoldering wick I was trained to pull out about 1.5 feet of it from the spool and leave it attached to the spool then pinch the wick with your thumb and finger with both hands placed about 3/4 of and inch apart and push in like your trying to loosen up the braides.

                            This will make the desoldeirng wick perform better and suck up more solder with less heat.

                            Too much heat from the soldeirng iron will destroy the parts your trying to save and lift the metal ciruit paths.

                            I will come back to this thread as I get more time, I am also working on my car or researching a title issue with it for now.
                            2007 Ford Crown Victoria LX Sport

                            Comment


                              #15
                              Honestly with the old JBL factory amps I have not had cap problems. Every single one has been the STK amp module. Frankly I'm amazed that I haven't had cap issues with them. Its near 30 year old gear with a switch mode power supply inside.

                              Stuff that doesn't use those stupid amp chips is more likely to be caps or solder joint problems though. Depends on construction. The JBL amps were surprisingly well built, Nichicon caps, lots of stand-offs to support the boards, well flowed joints. I've seen other stuff that was pure garbage inside though. The ones with almost no board support that let the leads on the output devices flex and crack are awesome. A lot of them have input jacks crack loose for the same reason, poor mechanical support and it just breaks loose. Cars are a tough environment and if you don't have good physical construction the rest of it almost doesn't matter.


                              vacuum desoldering guns are your friend. Use one and you'll never use the wick again.
                              86 Lincoln Town Car (Galactica).
                              5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                              91 Lincoln Mark VII LSC grandpa spec white and cranberry

                              1984 Lincoln Continental TurboDiesel - rolls coal

                              Originally posted by phayzer5
                              I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                              Comment

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