Don't Miss

JBL SUB 135 Woofer Speaker Repair

By on August 29, 2017
electronic repair bench for technicians











sub woofer speaker repair

My sister bought this JBL Sub 135 Woofer amp at a garage sale for $20. It was missing the fuse cap so I replaced the fuse holder with a new fuse holder to see if that was all that was wrong with it – it wasn’t. After I replaced the fuse holder, I attached my test light to it and powered it up through my Tenma variable Isolation transformer. As you can see in the photo, it has a short somewhere in the power supply. I decided to repair it for her birthday present.

You can tell by looking at the bottom of the darkened PCB that some components shorted. So I decided to pull the main power transistors first and then check the rest of the components. The bridge rectifier, transformer, speaker, and relay checked out fine. The ESR was too high in many e-caps, including the two primary 6800uF e-caps, though none of them were bulged. So I replaced them all.

how to repair sub woofer

Atlas DC Pro tester

The Q107 #TIP35C is the NPN, and the Q108 #TIP36C is a PNP transistor. Datasheet is here. I ordered some new ones from AliExpress. I also replaced Q105 #SB649A-PNP and Q106 #SD669A-NPN “Datasheet” with new transistors with the same part numbers when I ordered the power transistors. AliExpress is the only place I could find them. I forgot to take photos of testing them though.

how to fix subwoofer

I replaced the dual Op-Amp #NJM4558D with #MC1458P. I checked all of the diodes, zener diodes, resistors, and ceramic caps and replaced the bad parts. All of the diodes were good, but several of the 1/8 watt resistors were bad. Some of the resistors around the main e-caps had crumbling insulation. I guess the glue on the e-caps was eating them up, so I replaced all that were questionable or even had missing color marking.

One of the ceramic caps was shorted. Who knows how much time I could have wasted trying to find the fault had I just assumed all of the ceramic caps were good? I think it’s faster to just straight away replace them all. But I was curious about them, and checked them all just to see what I would find. The green 104J Mylar cap C107 needed replaced.

Below is a small photo of me testing a zener diode with my trusty Duoyi DY294 transistor/Insulation tester.  It will test a zener to around 1000 volts.

how to fix sub woofer

how to check zener diode

subwoofer circuit board

how to fix and repair sub woofer

electronic repair bench

fixing subwoofer

As you can see in the photos, I got it soldered up and put back together. It is looking good so far. Now I just need to get it back into the cabinet, plug up the woofer speaker, and see how it sounds.

repair subwoofer

The sub-woofer is now kicking some serious bass! It’s time for me to get back to my other articles. I hope you guys enjoyed this one. Below are some extra photos.

heat compound in circuit board

subwoofer circuit board repair

jbl sub135 subwoofer repair

repairing jbl 135 sub woofer

fixing jbl 135 sub woofer

robert calk junior

Robert Calk is a hobbyist from the USA who loves Electronics, Leatherworking, and Watchmaking

Please give a support by clicking  on the social buttons below. Your feedback or comment on the post is welcome.

P.S- Do you know of any your friends who would benefit from this content that you are reading now? If so, forward this website to your friends or you can invite your friends to subscribe to my newsletter for free in this Link.

Please check out his previous repair article below:




  1. Parasuraman

    August 29, 2017 at 11:31 am

    Great hunt! Very informative!

    • Robert Calk

      August 29, 2017 at 12:31 pm

      Thanks Parasuraman.

  2. Angelo

    August 29, 2017 at 11:40 am

    Great job sir
    very very informative article..
    as we all know that there are so many types of capacitors
    but the question is
    whic type of capacitors get shorted or dead soon or they become weaker with time?
    Thank you

    • Robert Calk

      August 29, 2017 at 1:22 pm

      Thanks Angelo. It is usually other components shorting that knocks out ceramic caps. There are manufacturing flaws sometimes.

      • Byron Filer

        March 20, 2019 at 1:22 am

        I have 2 of these that are in need of repair. What would you charge?

  3. Lee

    August 29, 2017 at 11:41 am

    Nice one Robert.

    • Robert Calk

      August 29, 2017 at 1:23 pm

      Thanks Lee. I'm glad you enjoyed it.

  4. Albert

    August 29, 2017 at 3:00 pm

    I always like to read about new devices or tools you use in your great articles Robert. I still must build such a Tenma isolated variable AC power supply myself because once in awhile I needed one. Like when those 6V AC operated UFO fibre lamps need a repair. But in that case of course have to build or buy a 230VAC model. Well done repair! I own a similar Logitech 5.1channel 500 Watt amplifier with THX sound, ideal when watching movies or playing XBOX games! Your sister made a good deal for only $20 now you fixed it. The LM1458 you used even has a short circuit protection integrated. About the DY294, mine goes up to about 1586V DC which is much higher than the 1000V Zener test you mentioned. Even if the Max scale setting on the selector of our great DUOYI device only shows 1000V.

    • Robert Calk

      August 30, 2017 at 3:42 am

      Hi Albert,

      Thanks. I bought the Tenma Isolation transformer new and prebuilt. It's very dangerous to work on live devices without going through an isolation transformer. I noticed that about the Op-Amp when I was checking out the datasheets. My DY294 also goes that high but figured that all of them would go at least 1000V. 1000V test for a zener should be good enough for just about anyone. I'm glad you enjoyed the article.

  5. Anthony

    August 29, 2017 at 6:07 pm

    Good on you Robert for resurrecting the cheap buy your sister bought for $20 ! Just wondering what
    cost all up the replacement parts cost you....not that it matters that much when you only paid $20 for
    the item and what satisfaction you get when it roars back to life ! Thanks for sharing your articles here
    with us Robert!

    • Robert Calk

      August 30, 2017 at 3:51 am

      You are very welcome, Anthony. I'm glad that you enjoyed it. When I buy components I buy more than I need so that I have some on hand in case I need them in the future. I got the transistors plus extras for $14 from China. I ordered some 1% 1/8w resistors because I didn't have very many. I already had the Mylar cap and most of the ceramic and e-caps. I probably only paid a couple of bucks for the fuse holder and fuse. I bought a bunch of them a long time ago and don't remember how much they were. I would guess that about $20 - $25 is what it actually cost me, not counting my time.

      • Robert Calk

        August 30, 2017 at 3:55 am

        I forgot the two 6800uF e-caps. So $30 - 35.

    • Anthony

      August 31, 2017 at 10:58 am

      Good on you Robert for a quite economical repair....nothing wrong with that outcome !

      • Robert Calk

        August 31, 2017 at 9:35 pm

        Nope, no complaints here. My sister is happy that her $20 investment wasn't wasted.

  6. suranag Electronics

    August 29, 2017 at 6:27 pm

    Hello Mr,Robert

    Very Nice and great Audio Sub Woofer Repair

    • Robert Calk

      August 30, 2017 at 3:57 am

      Thanks, I'm glad you enjoyed the article. Is your name Suranga, or Suranag?

  7. Des Gilham

    August 29, 2017 at 6:42 pm

    Nice being able to able to repair that unit and a bargain buy for that price where you come from. Not going to happen here, though.

    • Robert Calk

      August 30, 2017 at 4:04 am

      Thanks, Des. I guess $20 wasn't too bad. I would not have paid that much though. I would have talked him down to $10. Anyone that has one should check the thermal paste under the heat sink.

  8. Yogesh Panchal

    August 30, 2017 at 12:38 am

    Good deal at $20 with additional joy of repair!
    Thanks for sharing.

    • Robert Calk

      August 30, 2017 at 10:15 pm

      You are welcome, Yogesh. I'm glad you enjoyed it. Many of the repairs I do are not really worthy of an article. My sisters birthday was the main reason to repair the Sub 135, but the other reason was so that I could write an article about it.

  9. Humberto

    August 30, 2017 at 1:50 pm

    Hi Robert, I`ve really enjoyed reading your article, by the way, good pics.

    • Robert Calk

      August 30, 2017 at 10:23 pm

      Thanks, Humberto. I'm glad that you enjoyed it. Every photo in this article was taken with my FujiFilm FinePix SL 1000. Most of them were taken with the camera on a tripod.

  10. Tyrone.

    August 30, 2017 at 8:24 pm

    Thank you Robert for this article which I have enjoyed reading.This kind of article encourages and enlightens me very much.

    • Robert Calk

      August 30, 2017 at 10:34 pm

      You are welcome, Tyrone. I'm glad that you enjoyed it and am more happy that it encourages and enlightens you. That's why I write the articles, so that others will buy Mr. Yong's e-books and learn how to repair devices like I did. It's a great feeling to bring a wounded device back to it's former glory to provide happiness to people. It also helps people save money because they don't have to buy new devices. The smile from a baby that gets their toy fixed is priceless!
      Just don't work on any live device without an isolation transformer. An isolation transformer should be #1 on the equipment list for anyone that is interested in repair. There are videos on YouTube and the Net for those that want to build their own. Either way, you must have one.

      • Parasuraman S

        September 1, 2017 at 2:57 pm

        I have been using an isolation transformer for my work table for many, many years now. I got it replaced recently, as the old one developed problems. Except the CRT oscilloscope (for reasons you might already know for sure!), everything gets connected to it.

        • Robert Calk

          September 2, 2017 at 8:36 am

          Hi Parasuraman,
          My isolation transformer has it's ground tied to the ground of the wall and device input plug. So I still have to be careful with grounding. I wouldn't want to power my oscilloscope and my isolation transformer with the device under repair plugged into it through the same ground or I might blow my scope. Many people don't fully understand grounding, but they need to. Our friend Gerald Musy wrote an article touching on ground here :
          I advise everyone to read it and study about grounding, especially people new to the blog. There are also Youtube videos about grounding. I wonder how many people have blown their scopes because of grounding and don't even know what happened?

  11. Ulises aguilar pazzani

    September 7, 2017 at 11:46 am

    Mr Calk, great job Sir You make a new board great job

    • Robert Calk

      September 8, 2017 at 2:38 pm

      Thanks, Ulises. Thanks for taking the time to comment.

  12. Debra Calk

    September 20, 2017 at 4:56 am

    Thank you Robert for fixing my woofer for my birthday, your sis Debbie

    • Robert Calk

      September 28, 2017 at 1:57 am

      You are welcome, sis.

  13. Mike Adcox

    April 10, 2018 at 5:55 am

    Robert, I just bought this exact sub today for $20 and it is missing the fuse and fuse cap as well as several of the speaker clips were broke just like this one... Where can you pick up a fuse cap? If that doesn't help it power on where would be a good starting point as to what to look for to fix this? I am definitely not an seasoned electronics guy like yourself but I am a fast learner and can usually figure things out (although it may take me a while) 🙂 If you can email me with some pointers that would be fantastic... I'm glad that I found this! Thank You Robert! Fantastic work!

  14. Tonytitan

    June 23, 2020 at 9:53 pm

    I just obtained on of these with this problem: as soon as it's plugged in the greed led lights and stays on regardless of the position of the on/auto switch or the on/off switch. The relay never clicks in like it does on my other sub136 units. I'm guessing here, but I think it's in protect mode with blown power transistors. If swapping them out is not the fix, where should I look next?

  15. Juan Febres

    March 27, 2022 at 8:42 am

    I'm so glad to find this page, thank you for such informative repair. I have a JBL sub that stop working, I believe for the same reason. The board is identical to this one, although its a different model (SUB200). Mine still turns on for now, but I believe is about to finally pop because the PCB is darken around those 2 watt 330ohm resistors (R146, R149), the relay doesn't actuate, and last attempt to run measurements on it (live) I saw smoke coming out from a tiny resistor. I guess I will have to do the same you did... Thanks again!

  16. Robbie

    November 1, 2022 at 9:30 am

    Hello Robert,

    I have the same sub and it has crackling sound when the subwoofer is powered on with no input. Noticed that a couple of large resistors R146 & R149 are burned and I can’t tell the value because the code lines are invisible. By any chance do you know the values for these resistors? Thanks! Robbie


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.