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Test Equipment

Discussion in 'Shock Brother's DIY Amps' started by linux, Oct 4, 2018.

  1. linux

    linux TDPRI Member

    Age:
    69
    27
    Oct 3, 2018
    Evans, Ga.
    So I'm embarking on my first amp kit build (haven't decided on the kit but it will be simple). As I'm an old retired EE, I'd been thinking about constructing an electronics workbench as a hobby anyway so this is my opportunity/excuse.

    As with guitars, the trick will be concealing the number of orders and costs from the chief of staff, but that's another post.

    I own a DMM and that's pretty much it for TE, but I can probably assemble the kit and make it work just fine. The list of equipment that I'm thinking I should have is (at a minimum):

    1. Oscilloscope
    2. Waveform Generator
    3. THD monitor (not sure about actually needing this, certainly at first...)
    4. Dual power supply
    5. Variac with current display (for bringing up new designs slowly)
    6 2nd DMM

    It appears that most of this stuff (especially O-Scopes) have come down in cost a 'lot' since I was designing (~1980) when a decent Tek or HP scope would fetch many thousands.

    So what brands and styles of TE do people like?
     

  2. jtcnj

    jtcnj Tele-Meister

    Age:
    54
    407
    Feb 2, 2015
    Brick, N.J. USA
    Just repeating the advice I have received here:

    DIY light bulb type current limiter is a must have for start up.
    non conductive probe sticks: "chop sticks"
    Power filter capacitor voltage drain tool - resistor on the end of clip lead.

    Review of safety procedures / startup procedures

    Search this site or Google will give more detail on the above.

    Just my opinion:
    scope and signal generator nice to have if you need it.
    THD - your ears are likely good enough.
     
    King Fan and the fatch like this.

  3. linux

    linux TDPRI Member

    Age:
    69
    27
    Oct 3, 2018
    Evans, Ga.
    Ha Ha, I was actually planning on going out for Chinese to procure a set of chop sticks tonight!

    I saw a pic of the light bulb on some site. How does that limit current?
     

  4. dunner84

    dunner84 Tele-Meister

    262
    Jul 15, 2014
    Victoria, bc
    -Good DMM. I use a fluke 87.
    -Digital oscopes have come way down. A nice siglent 2 channel scope is pretty inexpensive.
    -to keep cost down, a sig gen isn't really needed. There are lots of way to generate a (proper for amp purposes) sin wave.. phone apps etc...
    - variance Is very handy, and cheap.
    - a proper dummy load!! You don't want to hear that tone on any amp at full volume....
     

  5. jtcnj

    jtcnj Tele-Meister

    Age:
    54
    407
    Feb 2, 2015
    Brick, N.J. USA
    Good reason to go out for Chinese food.
    Need chopsticks - Ya thats the ticket!
    any wood dowel or slim artist paint brush or similar will do.

    The light bulb filament is in series on the hot AC leg, if I recall correctly.
    The bulb will glow a bit under load, varies with amp model, but will light bright if your build has a short.
     
    Last edited: Oct 4, 2018

  6. jtcnj

    jtcnj Tele-Meister

    Age:
    54
    407
    Feb 2, 2015
    Brick, N.J. USA
    light bulb limiter.png Search Uncle Doug on youtube for a series of amp builds, very helpful.
    He has one on the light bulb limiter, and there are plenty others.

     
    flyswatter likes this.

  7. linux

    linux TDPRI Member

    Age:
    69
    27
    Oct 3, 2018
    Evans, Ga.
    So simple it's genius. Thanks!
     

  8. corliss1

    corliss1 Friend of Leo's Gold Supporter

    Sep 13, 2008
    Lansing, MI
    I have 1, 2 and 5. 6 happened when I knew what I needed later on after some experience and just have the old one still just in case. No need for a distortion analyzer unless you're working on hi fi stuff where we *don't* want some of that in the signal.

    My DC power supply is 2 channel, 20ish volts each, so I can get to 40ish volts if I put them together. If I need something more than that I grab a spare transformer.
     

  9. Junior Little

    Junior Little TDPRI Member

    45
    Jul 26, 2018
    Chucktown, SC
    I use one of these when I use my scope and signal generator, or, if I don't want to have the sh*t scared out of me poking around checking voltages...
     

  10. linux

    linux TDPRI Member

    Age:
    69
    27
    Oct 3, 2018
    Evans, Ga.
    Ha, didn't think of it like that. You're right, I probably don't need the distortion analyzer!
     

  11. linux

    linux TDPRI Member

    Age:
    69
    27
    Oct 3, 2018
    Evans, Ga.
    I know what you mean. Most of my design career was digital, where high voltage was 12v. I do need to be mindful of the realities here.

    I like this guy; watched a couple of his videos and wondered about his dummy load, so now I have a tutorial, thanks.
     
    Junior Little and RustySterling like this.

  12. linux

    linux TDPRI Member

    Age:
    69
    27
    Oct 3, 2018
    Evans, Ga.
    So what do people recommend for a good O-Scope now? I'm inclined to get an old Tek 465B for maybe $300 but have not yet compared to the newer slimmer (entry level?) scopes that cost about that new. Would certainly free up some bench space.
     

  13. Nickfl

    Nickfl Tele-Afflicted

    May 24, 2016
    Florida
    ESR meter, maybe a dedicated capacitance meter. A transistor tester if you're going to build pedals.
     
    dogmeat likes this.

  14. Phrygian77

    Phrygian77 Tele-Afflicted

    Apr 30, 2016
    Crawfordville, FL
    Because, it's a low resistance, and if you have a short, that will be a near zero resistance. The light bulb limits the amount of power that the short can draw. So, with a dead short, the light bulb lights up and you know you have a problem.
     

  15. VintageSG

    VintageSG Friend of Leo's Ad Free Member

    Mar 31, 2016
    Yorkshire
    Bias probes and a third multimeter. You possibly can have too many meters, but it's unlikely.
    One meter to monitor the voltage, one meter per power valve makes checks and adjustment a doddle. You only need two bias probes, even for a quad amp.
    Illuminated magnifier.
    Large box of patience, kept within easy reach.. Very handy when tracking intermittent signals...
     

  16. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    I used a 465 for many years for work many (many) years ago, love them. But the possible downside is that the last year of production was 1983, so the best you could get would be 35 years old... depending on how many hours are on the crt you could luck out and be fine, or not.
    For that reason (and because I found a deal) I picked up a nice Tek 2247A on eBay, which is about 12 years newer than a 465, and a great model.
    Pics: NSD!

    Still, I think lots of folks get good used 465 scopes and are quite happy with them. As far as the newest digital scopes in that price range, I briefly checked some out online; they looked ok, and might be worth checking out too, but I was a bit nostalgic for a Tek.
     
    Last edited: Oct 5, 2018

  17. GorgeousTones

    GorgeousTones TDPRI Member

    69
    Oct 17, 2015
    Boston
    I posted a nearly identical topic/question a couple years back, before I had built my first kit amp.. But once I got busy building my amp I discovered that some purchases went totally unused. I get the sense that you’re like I was; setting yourself up with a workspace to (hopefully & successfully) go further than one kit and do a lot more of this stuff..

    If I’m right about your intention to get into diy amp building more in depth down the line.. Then I would suggest holding off on purchasing the analytic testing equipment. And putting your money into the things you’re going be using over and over. Things like a serious soldering station, real high quality wire strippers ect.. Sounds obvious, but really can be the difference between an enjoyable, steady build. Or a slow going headache filled process marked by burnt fingers, damaged components, and unnecessary frustration along the way!

    Things such pricey scopes, signal & waveform generators, variacs can be handy sure.. But it likely won’t be used at all for your first kit or two. You’ve got time, and can pick up that stuff if you need to later. For now, leave that gear to seasoned pro’s & design engineers benches.:D
     
    King Fan likes this.

  18. corliss1

    corliss1 Friend of Leo's Gold Supporter

    Sep 13, 2008
    Lansing, MI

  19. sds1

    sds1 Tele-Holic

    Age:
    42
    658
    May 4, 2017
    Orlando, FL, USA
    For me, in this order:

    1) DMM
    2) Light Bulb Limiter
    3) Scope/Signal Generator/Dummy Load

    ^ those 3 all go together

    Haven't felt the need yet for:

    1) Variac
    2) Power supply
    3) Cap draining tool

    Could make great use of:

    1) ESR meter
    2) 2nd DMM
    3) Frequency analyzer

    And I totally agree with @GorgeousTones that investing in a nice solder station, wire cutters, and wire stripper is essential if you haven't done so already! Get some decent solder too. My first build would be MUCH better off had I heeded this advice.
     
    King Fan likes this.

  20. ranjam

    ranjam Tele-Holic

    600
    Dec 29, 2015
    Canada
    This is what I've been doing for decades;
    1. Visit http://www.arrl-ga.org/clubs.php and note any hamfests in your area.
    2. Meet some new friends.
    3. Buy up a bunch of old test equipment on the cheap.
    4. Learn how to restore all that cheap ham gear. ;)
    The only thing not mentioned yet (unless I missed it) is a handful of decade boxes. Always nice to have, and small enough not to take up valuable shop space. An old-school VTVM, and not a $$$ Fluke, is handy for troubleshooting tremolo circuits, and testing potentiometers. Oh, and make your own 'bias probe' from a dead octal tube and a socket.
    It's awesome to advocate $$$ equipment like a Fluke or a Tektronix. But completely unnecessary. The book American Guitars had a photo of the original Fender amplifier 'lab' showing someone working on a Deluxe Reverb(?) as if he knew what he was doing. No fancy equipment, but good, solid and reliable equipment (for the most part) that told the information that was needed. The annotations are mine, trying to ascertain exactly what was used. It was pretty simple, and one shocker was the crappy Eico 460 oscilloscope. I wouldn't be that cheap. Heck, he even has a piece of paper taped over the visor to try and get the lousy trace slightly more visible. :rolleyes:

    [​IMG]
    Try and pick up a few goodies, use 'em, and figure out what feels right to you. And figure out which pieces you can trust. Did anyone mention a tube tester?
     

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