PC board fragility

Discussion in 'Amp Central Station' started by Kuroyama, Sep 6, 2013.

  1. Kuroyama

    Kuroyama Tele-Meister

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    For years Ive accepted that brand name tube amps = quality. Tonewise thats proven to be mostly (if subjectively) true. It was for that reason I spent more than I wanted to and bought a Fender Princeton Reverb RI. It lasted for almost 3 weeks before I smoked it on week 3.

    Now Im shopping for its replacement, but am leery (gun shy?) of amps built with PC board. Ive got a Fender Deluxe on the line for 350, but read that its tube sockets being attached directly to the board is a real weak point of construction. Since the amp I seek now will spent much of its life bumping in the back of my SUV going to and from practice every week... Maybe a tube amp isnt the way to go? Or am I just being overcautious after being burned?

    As a note, my heavy hitter is a '94 Twin which is a 100W of tube roar that breaks my back to carry and my nerves as it bumps and jostles when I take it out of the house.

    Did anyone else here give up on tubes for their portable amps because of fragility?
     
  2. Sherpa

    Sherpa Tele-Holic

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    I think it depends a lot on the quality and thickness of the boards used. There are a number of premium amp manufacturers that mount the tubes to the board as opposed to the chassis. Although I prefer the latter, I've had no problems whatsoever with my Mesa Boogie and Koch amps using the former construction. They take great care with their soldering, and use milspec double-sided extra-strength boards, which seem to dissipate heat well, and shouldn't really flex unless you have a gorilla swapping out tubes for you... ;) If memory serves, Soldano, Carvin, Marshall, VHT, and Orange also mount the sockets on the board in at least some of their models.

    Here's a great summary from Aiken:

    http://www.aikenamps.com/PCBorPTP.htm
     
    Last edited: Sep 6, 2013
  3. Cat MacKinnon

    Cat MacKinnon Friend of Leo's

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    i'll second what Sherpa said. there are pros and cons to every type of amp wiring choice, but overall as long as the manufacturer didn't cheap out on the specs, they're all pretty reliable for the most part.

    are PCB-mounted sockets weaker than chassis-mounted ones? technically speaking, yes...but it's all relative. good amp manufacturers will make sure that the sockets are soldered as solidly as possible, and as long as you insert/remove tubes properly it shouldn't ever be an issue. all a PCB does is take the place of hookup wire and turrets (or eyelets, or point-to-point): otherwise it serves the exact same function as turret/point-to-point wiring. it just makes it easier to assemble amps, because it cuts out a large amount of handwork that generally causes the price to go through the roof. in some ways, a properly-designed PCB can be a lot less problematic than a PTP or turret/eyelet type of construction, because you don't have to worry about routing the wires incorrectly (which causes all sorts of hum and noise), there are less wires to potentially come unsoldered and short out and stuff like that. just because an amp is hand-wired point to point (or turret/eyelet board) doesn't mean it can't fail, and in fact there are potentially a lot more places for it to fail than with PCB.

    most good amp manufacturers that use PCBs most likely specify a high number of insertions before a potential socket failure. in other words, they'll design the board so that tubes can be changed many, many times before it starts weakening the socket solder joints. most likely, that spec is higher than you'll ever go...in other words, you'll probably never change the tubes enough times to weaken those joints. they over-build the PCB and sockets so they shouldn't ever cause problems under normal use, or even heavier use (like a touring band that may change power tubes several times a year or something like that.)

    obviously there are times where sockets fail and yank out of the board, or crack solder joints. it can either be through "user error" (ie, you're not inserting/removing tubes properly), or the board wasn't designed or spec'd properly. it happens, but most manufacturers that discover a consistent problem with a run of amps will fix or replace the PCB (another upside to circuit boards is that it makes major swaps like that really easy and fast.) it's almost never the PCB itself though (anyone who's ever had to cut PCB can testify to just how strong and hard to work with they can be!) it's usually the solder joints that hold the socket in, but a proper solder joint is incredibly strong too. i'd imagine most manufacturers specify stronger solder as well, because it's far less expensive to build them right the first time instead of having to fix a bunch of amps that are returned for warranty repairs.

    anyway, tons of manufacturers have been using PCB-mounted tube sockets for a really long time now and rarely is it a problem. like i said before, it's technically weaker than a chassis-mounted socket, but that's all relative: generally speaking, it's still more than strong enough and not something to worry about (unless you're going to buy a used amp that may have a history of socket problems with that model or something.) as Sherpa pointed out, there are lots of big-name (and well-respected) manufacturers, some of whom make very expensive amps, that use PCB-mounted sockets. they employ engineers that design the circuit boards to be as reliable as possible...otherwise they'd be shooting themselves in the foot and ruining their reputations if they made crappy PCBs that popped their sockets all the time.

    two things to remember: first, make sure you're removing tubes properly. the correct way to remove a tube (no matter how the socket is mounted) is to gently rock the tube in a circular motion as you're pulling it out. never just yank a tube straight out of a socket, since you can damage the socket, or pull pins or the whole base right off of the tube (and Murphy's Law says it'll probably be an expensive power tube that you break, because Murphy's a dick like that:lol:.) when you insert a tube, make sure the pins are lined up with the proper holes in the socket and the "key" on the center pin is matched up properly to the hole in the middle of the socket.

    second, if you drop an amp with PCB-mounted tube sockets, check the sockets to make sure you didn't crack or break the solder joints. if the amp takes a fall, it can put a lot of stress on tube sockets because of the weight of the tubes. if you turn the amp on and it makes all sorts of weird noises (or no sound at all), immediately turn it off. take it to a tech so they can open it up and check the solder joints, and resolder them if necessary.
     
  4. dporto

    dporto Tele-Meister Silver Supporter

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    " It lasted for almost 3 weeks before I smoked it on week 3."

    You don't mention why it "smoked"...? What exactly "smoked"? Power transformer? Output transformer? Tube(s)? Resistors? Did it "smoke" while you were playing it? Or, it didn't work when you turned it on? Also, you didn't mention it but I'm assuming at 3 weeks old it's covered under warranty? The Princeton Reverb just may be a bit under powered for your application (especially if you're used to running a Twin...). I don't really see what a PCB has to do with it - unless it was a faulty one to begin with.
     
  5. Bongocaster

    Bongocaster Friend of Leo's

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    OK, I'll roll with you (and/or rock as the case may be) on tube sockets. Now pots and jacks that are used all the time. I say keep them off of the PCB.
     
  6. Jared Purdy

    Jared Purdy Friend of Leo's

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    If you are after the black face Fender sound, but want something more durable (but at a reasonable price point) you might want to consider the Mesa/Boogie Lonestar Special. It too is made with PCB, but the tube sockets are not connected to the board. Robust, amazing tones. Otherwise, check out Vintage Tone Amps. Rick Hayes makes hand wired copies of BF amps, and I have read that his work is excellent. His prices are certainly reasonable. There is also Headstrong Amps and Allen Amps, though if you want a near copy of the Fender BF then Vintage Tone might be what you are after.
     
  7. leebman

    leebman Tele-Meister

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    You must have gone hardcore to kill the princeton, I'd check it wasn't faulty in some way before you spend any more cash on an amp if you wiped that amp beyond repair in such a short amount of time its probable you need an 6l6 driven amp not a 16watt practice amp!
     
  8. backline

    backline Tele-Afflicted

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    Not sue what you are worried about.....
    Why dont you buy a tube amp that is hand wired then.?
    Too be sure...there are many well made PCB amps. Mike Soldano and Andy Fuchs come to mind.
    My Voc AC30CCH is a well made PCB and fairly easy to work on and repair.
    good luck.
     
  9. alnicopu

    alnicopu Friend of Leo's

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    Here's my take. An even bigger problem is plug type connections to PCB designed amps. Poor connections cause resistance at the plugs. They plug directly to the board. With resistance comes heat. With heat comes burnt traces at the connectors. As the traces burn you get more resistance and heat which just compounds the problem. Pretty soon traces discolor then lift off the board. I use a thick piece of resistor lead to bridge them but sometimes have had to use a piece of wire. I see this ALL THE TIME at my day job. Even 5v logic lines will drop too low because of this. When I work on a circuit board amp I disconnect and reconnect every plug type connection in there right after I yank out the chassis.

    Circuit boards are "ok" if left to themselves. There would be no flexing if the tube sockets, speaker jack and input jacks were isolated.
     
  10. alnicopu

    alnicopu Friend of Leo's

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  11. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    The Space Shuttle utilized an awful lot of PCBs... ;)
     
  12. Mike Simpson

    Mike Simpson Doctor of Teleocity

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    And only one of them blew up...
     
  13. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    That was an O-Ring failure, not any PCBs involved in that one.
     
  14. tekbow

    tekbow Tele-Afflicted

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    I'm not too fussed, as long as something is designed for durability rather than low unit cost/max profit..

    Soldano was mentioned, case in point, sockets are PCB mounted, but huge wide traces, thick board, and pots are chassis mounted and jumpered to the appropriate point on the PCB. If it was all P2P I'd like that just as much. Either method done badly is going to be a pain. But the thing is P2P is so labour intensive that it's just not done cheap. It costs to do, and the people who do it know what they're doing.

    This is why i think you don't see a badly done P2P commercial (or custom) amp as opposed to it being "better".

    Actually was wrong about the sockets being board mounted, and in the case of the HR50+ the pots are board mounted. but look at it. I still trust it.
     

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  15. Mike Simpson

    Mike Simpson Doctor of Teleocity

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    That's the story they're stickin to... I bet there is a PCB in the machine that made the O ring...
     
  16. Mike Simpson

    Mike Simpson Doctor of Teleocity

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    Look for a silverface Fender and have it serviced.
     
  17. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    This is the very reason why so many people slam on PCB construction. Higher-end amps can be turret board, PTP, or PCB, and all will be quite durable as the components are all of high quality.

    Cheap amps, on the other hand, are almost always going to be PCB, but they also skimp on all of the components, including the board itself. The failure rate is due to the use of cheap components and construction, not because they happen to all be mounted to a circuit board.
     
  18. Alamo

    Alamo Doctor of Teleocity

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    How many hand-wired, ptp, all tube rockets took off? :lol:
     
  19. tekbow

    tekbow Tele-Afflicted

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    Thankyou, exactly the point i was trying to make, but you did it more eloquently and in half the space
     
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