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Amp troubleshooting, flabby bass ( AC15c1)

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  • #16
    I can't imagine going through the trouble of swapping out an amp's innards to circumvent a problem with warranty support. It's not as if two wrongs can make a right. That said, some people will do anything when they're driven to desperation.

    I agree with Chuck on the problem of planned obsolescence, consumerism, and disposable widgets. It's a pet peeve of mine. I heard a commercial on TV that said that 50% of all manufactured goods produced in history were produced in the last 10 years. Think about it. That trend can't continue or we'll be living on piles of garbage.

    I hate disposable merchandise. I don't want to buy a new widget every year or to and contribute to the problem of dead widgets in a landfill. I want to pay top dollar to buy a quality widget that will last my lifetime. We all know that old Fender amps fall into this category. And even though Mesa amps get maligned a lot around here, I think that my Mesa Mk IV falls into the high quality / long life category. It's built with very high quality, it's very well supported, and it was built in America. There's a lot to like about the amp. It'll probably last my lifetime.

    I'm going to disagree with Chuck on the Chinese contract manufacturers building to the quality standards that are demanded of them. We all remember that things started off with everything being made in China being a PoS with shoddy workmanship and substandard parts. That problem is still prevalent today. Many a contract manufacturer over there will build to the lowest possible quality using the lowest quality parts they can get away with, in spite of what their customer requested of them.

    I'm sure that you guys have all experienced failures of a consumer electronics device that was related to the manufacturer's decision to use a low quality cap. I've had it happen more times than I can remember. I once had to replace a dead PSU cap on a DVD player that was one week out of warranty. What ticked me off about that was that I had a $20 DVD player die a week out of warranty because they decided to use a 2-cent no-name Chinese cap in the PSU instead of a 5-cent quality name brand cap. So I had to buy a 25-cent cap at retail and spend an hour fixing the unit to keep it out of a landfill and to avoid rewarding them by buying another one. This process has repeated itself with different consumer electronics items more times than I can remember. As a result, I try to avoid buying new consumer electronics. I feel like I'm being exploited whenever I have to give in.

    I have a family member whose job is quality control for a major US corporation. They order lots of contracted goods from Chinese manufacturers, and they've been burned several times by contract manufacturers skimping on parts when they don't think they'll get caught. To assure compliance and constant quality, my brother has to travel back and forth to provide on-site supervision of the contract manufacturers, otherwise his company can't get the quality that they need. The result is that he alternates spending 2 weeks abroad and 2 weeks at home, and half of his life is being spent in a foreign country, away from his family, supervising manufacturers who would skimp on production if he weren't standing over them with a club. That's what it takes to get consistent quality out of China. They don't have the American manufacturing ethic of building the best quality product. Their manufacturing ethic is focused on building the cheapest cost product that will pass a performance standard, and often those standards are set pretty low, in spite of what the contracting company requested.
    "Stand back, I'm holding a calculator." - chinrest

    "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

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    • #17
      Just scanned through all this. In no particular order:

      - Good on you for thinking first of replacing tubes. Replacing tubes with known good ones is nearly always step #1.
      - The money on new tubes was not wasted, as having a spare set of good tubes is one of the things that separates the knowledgeable from the naive on tube amps.
      - Suspecting caps is a reasonable thing. There are only two processes in a tube amp that lead to long time delays - capacitors charging or discharging, and thermal/heating effects. Thermal takes longer in most cases, but not always. Replacing caps pretty much removes these.
      - Enzo's right - what's new about that? - give the tech a chance to fix their missing the fact if you can possibly do so. A good tech is worth their weight in gold. Well, at least for the smaller ones. The bigger ones may be worth their weight in half gold, half silver, based purely on weight.
      - I would say to reflow all the joints next. Doesn't cost much, and a cracked joint opening with heat could cause the problem.
      - The black powder on the tube sockets is decidedly odd, but doesn't much sound like your problem. Maybe, but nothing comes to mind about that. Arcing damage is more of a trail than a burst of powder.
      - I suspect that the cap bypassing a cathode resistor coming open could cause loss of treble that would make the amp sound flabby by comparison. So might an open cap in the tone stack, not letting treble through. Both of these could be the cap, could be a cracked solder joint or trace. An open or shorted series coupling cap would do other things than just making treble go away.
      Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

      Oh, wait! That sounds familiar, somehow.

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      • #18
        Just a friendly reminder that this is an old thread and the OP hasn't been heard from in about a year, likewise for the other poster with the same problem.
        I have no problem with thread resurrections as almost all discussions on this forum are useful, however, I though I'd mention it as I get caught out myself by old threads on occasion .
        Originally posted by Enzo
        I have a sign in my shop that says, "Never think up reasons not to check something."


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        • #19
          thanks, i hadn't noticed the timestamp.

          so now i guess we can continue the hijack about china.
          "Stand back, I'm holding a calculator." - chinrest

          "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

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          • #20
            Just so long as no one gets anybody started about crate .
            Originally posted by Enzo
            I have a sign in my shop that says, "Never think up reasons not to check something."


            Comment


            • #21
              Originally posted by bob p View Post
              thanks, i hadn't noticed the timestamp.

              so now i guess we can continue the hijack about china.


              I once did some design work for an American company that I later found out intended to manufacture in China. I was hoping to go with Malaysia instead for this particular design and concept but the bottom line was to compete directly with amps like the Fender HR's, Peavey Classics and various Chinese made products. My market concept didn't meet this criteria. So... I did end up working out circuit refinements for another design they were considering. In the process I dealt directly with the manufacturer in China regarding quality issues that included exact part identification. This manufacturer was able to provide me with brands and part numbers that they could get easily enough to make them standard options. So if, for example, the power supply filters would ordinarily default to the cheapest available you could upgrade to something like a Panasonic part number for nothing more than the added part cost. The manufacturer was very good about this. And though I didn't go through and upgrade a lot of components, I did focus on areas I knew had been problematic for other production amps like the use of poor electrolytics. Because I was able to choose from a range of available components I could spec these upgrades with very little increase to the retail price. In the end my upgrades were rejected by the company I was working with. Shaving pennies off parts to reduce the retail by nickels?!?

              I should think there are laws in place to the effect that a Chinese manufacturer can't charge you for one thing and sell you another legally. But I also can't imagine you would lie about it happening. I still don't understand why the QC couldn't be done by inspecting products stateside and rejecting shenanigans. I suppose it's cheaper to have a full time travelling QC guy than it is to set up stateside distribution.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "If you're not interested in opinions and the experience of others, why even start a thread?
              You can't just expect consent." Helmholtz

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