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New here. Looking for advice on recapping a Peavey Mark III 400

Discussion in 'Amps and Cabs [BG]' started by Racerwoody, Jan 10, 2019.


  1. Racerwoody

    Racerwoody

    Dec 28, 2018
    First post. New bassist. Starting out with an upgraded Fender Squier Affinity P Bass. Upgraded tuners, bridge, pickguard, pickups...
    1967 Kustom 212 Cab , with pyle drivers.
    Peavey Mark III 400 bass head.
    My question is this. The Peavey is currently not working. It blows fuse. I'll be opening up for repairs, Pops is the electronic wiz, and I would like to recap it at the time of repair. I do understand I can get some more head room out of this amp with a higher value cap. I'm looking for info on what Caps to purchase, so I can have parts here when Pops comes to fix. Also, most likely offenders, Out put Transistors? If these arent' expensive, I'd like to have some stuff on hand. We have a pretty good collection of resistors and diodes and such here, but the transistors I am betting we do not have. Any help will be greatly appreciated. I'm currently learning on a little line 6 spider iii 15w/8" guitar amp, so I am highly motivated to get my "new " rig up and running . Thanks all! This is an amazing forum. Rock on!
     

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    Last edited: Jan 10, 2019
  2. Slidlow

    Slidlow Supporting Member

    Apr 15, 2009
    Oshawa, Canada
    Contact Peavey. They are pretty good at supplying schematics so you would have all the information you need to repair.
     
  3. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Don't go changing anything until you have identified all the actual problems and the amp is fixed and operating properly.

    There is probably nothing wrong with the caps, changing their values is not likely to improve anything and could unintentionally cause new problems since the protection circuitry considers the amount of energy storage within its design.

    The single biggest way that you can improve the sound of your amp is by taking lessons and practicing, the more you practice, the better your amp will sound.
     
  4. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    Welcome to TalkBass!!!!
     
    Artman and Racerwoody like this.
  5. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    Right on!

    Re-cap? We don't need no stinkin' re-cap! :smug:

    There are many Hi-Fi forums out there that have the re-cap mantra stamped all over them. Don't drink the Kool-Aid. Peavey's were built very robustly. In fact, I have several pieces of Marantz Hi-Fi gear from the mid 1970's that still have their original electrolytic caps, and have had some pieces tested by experienced techs who said they're fine.
     
    dBChad and Racerwoody like this.
  6. Racerwoody

    Racerwoody

    Dec 28, 2018
    Thank you. I have read many of your informed replies, I'm glad you replied. I have read many times on this forum, that these caps should be replaced simply due to their age. Is this not the case? I am just trying to be as prepared for Pops as I can. He is used to having a shop full of parts to pick from. Now that he is retired we are relegated to a few plastic totes with a hodgepodge collection of components.
     
  7. Racerwoody

    Racerwoody

    Dec 28, 2018
    Thanks!
     
  8. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    If lots of folks have had a specific item replaced, or if it's a known or common repair, then go ahead. Replace them.

    I was more or less calling attention to people blindly re-capping just because...

    However, if your pop has a drawer full of caps from the '80's or 90's, wouldn't they be just as suspect as the ones you want to replace? Get new manufactured ones. They're not expensive.
     
  9. Racerwoody

    Racerwoody

    Dec 28, 2018
    Just because of the age is what I was reading. It's an old Mark III, they didn't have that many issues from what I have read. I am excited. Picked up two amps needing repair for $30 each. This Peavey and a Genz Benz el diablo 60 head. Found some vintage 6L6's for it, (bought with no powerntubes. Lights up , but no output) Anxious to get them up and running.
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Don't replace anything until you know what's bad. Over 90% of recap jobs are purely a waste of money and is see a fair amount of damage due to guys who struggled with a recap job. Once things get jacked up, it's hard to make the amp reliable again,

    Most parts are still available for your Diablo 60 but not all parts.
     
    Artman and Cowboy in Latvia like this.
  11. Racerwoody

    Racerwoody

    Dec 28, 2018
    Thank you again. I'll post up next week what we find. I really appreciate the support!
     
  12. Cowboy in Latvia

    Cowboy in Latvia

    Mar 1, 2015
    I nominate this for true quote of the year. I know it's early but I doubt there's gonna be a better one.
     
    wave rider, Geri O, Artman and 7 others like this.
  13. Agedhorse, do you actually work on 20+ year old amps very often? I'm curious because you say this repeatedly, yet my experience is that for amps of the 80's and 90's, for an amp that sort of works but doesn't actually sound very good, or is lacking bass, replacing the electrolytic caps usually restores performance.
    Electrolytic Capacitor manufacturers also provide a shelf and service lifetime in the datasheets of several thousand hours in most cases and any older amp has certainly exceeded that. I'm not an EE but no other components used in amps I know of have anything like that specified.
    I'm just trying to reconcile my experience with your knowledge.

    I recently replaced all the smaller electrolytics in a peavey from the early 90's and the change was remarkable. Admittedly you could hear that at least one in the audio path was leaking. I left the main filter caps alone as the ones peavey installed were huge things that looked high quality.
     
  14. I don't think practice will make an amp that blows fuses sound better, but I do agree with the sentiment.
     
    Artman, dune2k, 31HZ and 2 others like this.
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Yes, actually I do see some of my designs from well over 20 years ago and almost never do I see a defective cap. This doesn't mean that they don't exist, but with quality parts (most caps used within the past 30 years are pretty good) it's quite rare.

    Electrolytic caps have a service life that's really quite long if you follow the design guidelines. In general with good design, 20,000 hours is not unrealistic. Now think about it for a moment, there are quite a few higher quality consumer products that are functioning well after 10 hours of 24/7 operation, that's 87,000 hours of continuous operation. Heck, the computer I'm using right now, while am industrial/commercial duty power supply, has been running 27/7 for over 7 years (over 60,000 hours) so it appears that these capacitors haven't gotten the message???

    Many of the amplifiers and electronics that I worked on over the years was in the cinema industry, I often worked on QSC amps that had over 30,000 hours logged on them and cinema processors (and their power supplies) that had easily as many hours. The alarm system in my shop has electrolytic capacitors in it, going on 12 years 24/7 (over 100,000 hours) and when I serviced sound systems in large public spaces such as airports, shopping centers and military installations, they operated 24/7 for easily 20 years (that's almost 200,000 hours).

    Common sense should show that something is grossly wrong when the internet jumps up and down screaming about how necessary re-capping any piece of gear is after a few thousand hours... it's become a hobby that's often looking for a problem to solve (ie. a project). IMO, a better project would be to just build something from a kit.
     
    UpperBout and mikewalker like this.
  16. saabfender

    saabfender Banned SUSPENDED

    Jan 10, 2018
    Indianapolis
    I've actually recapped the Mark IV version of this guy. It's in the other room. I've gigged with it a few times driving an 1810. It's a good one.

    After recapping only the PS section, it idled quieter and was noticeably louder and had an overall cleaner sound. The caps in mine were 35 years old and kinda cheap to begin with. Capacitor technology is way better now and nothing like that lasts forever anyway. Replace those old can multi-caps (ever cut one open?) with modern ones for an even more dramatic difference.

    However, I would never jack with the values. The guys who designed that amp had slide rules. You don't. Don't have to. Just order what's in it already from Digikey. Funny, I had the two big caps and three little ones of the correct values on-hand. $0!

    Leave everything else alone. Transistors, diodes, etc. are fine. I've yet to not be able to find a Peavey schematic online.

    Don't worry about having parts on-hand for your dad. He'll figure it out and go from there.
     
    Last edited: Jan 10, 2019
  17. saabfender

    saabfender Banned SUSPENDED

    Jan 10, 2018
    Indianapolis
    Mine was like this. Computers are awesome.
    peavey_400bh.pdf_1.
     
  18. Possibly your designs are better, or made with higher quality components than some others? Clearly it is possible to build electronics that will last a long time, and there are many examples. It is also possible to build stuff with lower quality components that leads to problems.
    Of the handful of amps I've fixed for myself, other than mechanical issues like jacks or pots the vast majority have been electrolytic capacitor problems, with a few resistors as well.
    This is predominantly discrete component amps from the 80's and 90's, that presumably have trouble from old age rather than abuse.

    Wholesale replacing caps for no reason is ridiculous, but for an old amp that isn't worth paying a tech to diagnose, or if you are too lazy to specifically go through and find exactly which capacitor is leaking, wholesale replacement of caps is a good option for someone competent at soldering. Although I personally would replace all the similar caps if 1 is leaking as they have all lead the same life.

    Something pushing 30 years old that was made down to a price is likely to be reaching the end of it's capacitors life in many cases so if you want it to work for another 30 years, it seems like a reasonable thing to do.
    I have a Marshall valvestate head that was clearly made down to a price. I got it cheap second hand and had to replace a few leaky caps when it was 5-10 years old. I got it out recently after leaving it sit for probably 10 years and tried to use it, and it clearly is full of leaky caps again, so when I get around to it, I'm simply going to replace all the electrolytics with the highest quality replacements I can get.

    I sort of rambled there but I guess my point is kinda that 30 years ago, there were a lot of lower quality caps around, maybe? And also that the internet will latch onto a grain of truth and blow it out of proportion.
    I don't have any experience with anything from the last 20 years though.
     
    Garret Graves and saabfender like this.
  19. It's blowing fuses. Clearly everything else is not fine. It needs to be properly diagnosed.
     
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    This is not something that I have seen, and I've been pretty deep into the service side of this industry for 40 years. I ran a large consumer electronics service center early in my career and saw some techs replace caps on every unit and other techs with better results replace maybe 1 cap a year. IMO, there is no question that almost all of those caps were completely problem-free. Like 99%.

    Do what you want to do, my (extensive) experience says otherwise. Fun fact, I have probably used about 5 million electrolytic caps in my career... you would think I would see some bad ones right? You have replaced more caps in your two amps than I have replaced in probably 20 years, that's has to be the worst luck I have seen with caps.
     

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