Amp Maintenance DIY

Discussion in 'Amps and Cabs [BG]' started by Jibudo, Jun 9, 2021.


  1. BoogieZK, I agree with expanding one's knowledge and being safely curious. You and I have the same background; you as an engineer, me as a technologist. When I was beginning my training at a young age, I envisioned a career being a TV repair man or working in a radio/electronics shop. By the time I graduated tech school I realized that there wasn't much money in those jobs and I went on to bigger and better career positions. Sadly, in North America at least, there are virtually no more 'local electronic shops' to go to. There are some places that fix computers and TVs etc but those tend to be places like the tech department/depot at Best Buy or Staples etc. Sadly, the small repair shops are almost extinct. Repair techs that know guitar amps or PAs, etc tend to work for the larger music stores and I suspect that they are few in numbers and are contract workers, not full time employees. In Canada we have a music store with facilities coast to coast. Where I live, the repair person is as old as me and moves from store to store through the week as their only amp tech. In my retirement years, I would have liked to have that job but the store only pays that one guy. I did that work 'on the side' for the enjoyment of it, making a few dollars too. Word spread by word of mouth that I was a "tube amp guy".
     
  2. I do virtually no maintenance on my amps other than light cleaning and dusting every few years or as needed. But I try to take good care of my amps, no drinks on or around them, avoid yanking on cables, those sorts of things.
     
    byacey and agedhorse like this.
  3. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I encourage learning about something before poking around.
     
    byacey likes this.
  4. I don't know of any technician that would encourage this; when things go wrong, the owner will be trying to hold them responsible for any damage that occurs.

    Once the cover is open, there is potential for unknowingly creating damage. You can't expect a technician to volunteer his time educating you about all the potential damage you might cause, and how to avoid it.

    If a person is hell bent on acquiring knowledge, they should enroll in some post secondary electronics courses and learn the basics, and then apprentice under an accredited technician. Or, they can poke around and worst case possibly have to buy another amplifier.
     
    Haroldo and agedhorse like this.
  5. BoogieZK

    BoogieZK

    Sep 28, 2008
    Toulouse, France
    Why is this making all this fur?

    Science be damned, people nowadays have superduper complicated smartphones, PCs, TVs and audio gear... It is the Numerical Era when kids are more interested in how to build things on Fortnite than talking IRL to each others and when i say:
    Take 5 minute of your pathetic musician life to dust off your amp with your soft skin hands, I am wrong?
    Yeah right, Burn me for that.
     
    Paul Szegedin likes this.
  6. Anyone can do anything they want with their own gear, at their own risk.

    As a kid, I didn't hesitate to dive into gear; I fixed some things, and I'm sorry to say, destroyed other things beyond repair. This was long before I had any formal training in electronics; it was part of the early learning process.

    With what I know now, and 40 years of experience behind me, I can't in good conscience recommend anyone without proper training to open up their own, or anyone else's equipment.
     
    agedhorse likes this.
  7. Gregc57

    Gregc57

    May 28, 2021
    NY, USA
    I do:
    Solid State, maybe just clean the jacks and clean/lube the pots. Call it good.
    Tube amp: Add cleaning and treating the tube sockets, retube as needed; check and if necessary adjust the bias.
    Recap every 10 or more years. Be careful in there. It can be deadly. I've been an electronic tech for ~ 40 years.
     
  8. LetItGrowTone

    LetItGrowTone

    Apr 2, 2019
    I am grateful for every reply I've received to threads I started about amp guts, but this is not the best place for that.
     
    Last edited: Jun 11, 2021
  9. nbsipics

    nbsipics Ours' is the only Reality of Consequence Gold Supporting Member

    Apr 8, 2016
    I’ve got a Walter Woods and this thread has inspired me to rip into it with reckless abandon...
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If you are only getting 10 years out of a set of caps, you have much bigger problem. Either a design issue or really poor quality caps.

    Quality modern caps operated within their ratings are capable of 30+ years. I use a design target of 40 years for electrolytic caps and for amps that are 30 years old have yet to see any issues.
     
    Passinwind, BassNugget and byacey like this.
  11. Even some older generation caps have still stood up to the test of time. Running in a cool environment and keeping ripple current to a minimum, they can go for many years.
     
    agedhorse likes this.
  12. chris_b

    chris_b

    Jun 2, 2007
    While this is true, most will sell on their gear when they are upgrading. So if someone has damaged or made an amp unsafe by attempting their own maintenance, they are not only playing dice with their own life but with the lives of future owners.
     
    byacey and agedhorse like this.
  13. LetItGrowTone

    LetItGrowTone

    Apr 2, 2019
    There is no way to avoid risk when buying used. So anyone intending to buy used and concerned about this should either get training to get competent to open it and inspect and test it to whatever extent desired, or have the item drop shipped to a tech.

    But even then, you know, the tech is also "only human"; there is no way to avoid risk when buying used.
     
    Last edited: Jun 12, 2021

  14. There was a time back in the 70s in Heidelberg, after a LONG weekend, that I felt like I just "might" need 60grit sandpaper..........what a weekend THAT was.......boy! Those were the days!! :thumbsup:
     
    agedhorse and LetItGrowTone like this.
  15. larrysb

    larrysb

    Mar 23, 2020
    $ilicon Valley

    Agree that electrolytic capacitors should definitely last more than 10 years. There's no need to re-cap a tube amp every 10 years, assuming quality parts are used.

    Quality - well, that's been an issue.

    Electrolytic capacitors are a life-limited component. They're rated in hours of life at a temperature. The temperature is the sum of ambient temperature and heat generated internally by ripple current. They all degrade, eventually.

    So 60 years ago, they made all kinds of capacitors, some very high quality, many not. That is true today too. The longer life, the higher the heat rating, the more you spend. So, you see the tradeoff right away.

    In the early-2000's a literal scandal broke out in the electrolytic capacitor industry, which includes industrial espionage, stolen chemistry formulas, unscrupulous parts markers you never heard of and highly overstated life ratings.

    The result was a lot of equipment was made with suspect components in the 2000's. In particular, high-ripple, low ESR capacitors used in switching power supplies and buck/boost regulators failed a lot. However, this extends to ALL equipment, from appliances to consumer products to musical equipment and everything else, ranging down to plain simple e-lytics of small values and low voltages.

    I bought a condo property that was built new in 2007 and never occupied. The ten year old appliances had never been used, just plugged in and clock running. They all had failed, no boards available from the maker. All the digital boards had a rash of bad capacitors. I just replaced them all with new, brand name capacitors and all the controllers came right back to life. The bad parts had excessive ESR and in some cases, were simply open.

    I know this affects some budget audio mixers from a known budget brand name...

    YMMV.
     
    Gregc57 likes this.
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Actually, the cap issue became quite overblown and was the topic of some sensationalist videos too.

    I somehow managed to design products manufactured in large quantities without ever running into capacitor problems. But, we used capacitors from known good vendors, we didn't grind the vendors for the cheapest price, we understood the rating metrics for the parts and designed well within these limits and their lifespan derating factors.

    The other factor that the sensationalists promoted was that the capacitors were rated for say 5000 hours as a finite limit. The reality couldn't be farther from the truth, since the rated lifespan of capacitors is based on de-ratings for temperature, ripple current, applied voltage and a few other factors, and the circuit itself can be designed to accommodate some mild degradation. Designing around these variables can take a simple 5000 hour rated part and turn it into a 50,000 hour rated part with little difficulty.

    I have a test amp that's sitting under my desk that has been on 24/7 for 10 years now. Zero issues, and this would represent over 87,000 operating hours, so clearly the design and choice of parts has a lot to do with real world reliability.

    Also, most of those defective caps were low voltage electrolytic caps, 16V or less. The caps in the amps I design generally start at 35V even though the operating voltage may only be 15 volts. I haven't seen any issues with the higher voltage caps operating within reasonable margins. Caps for tube amps aren't even part of what those companies even made, so that's a non-issue. There is a lot of misapplication of cap specs in the tube amp industry (except by the major players), this isn't a cap problem but is a design/applications problem.
     
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    Jun 22, 2021

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