So You Want To Repair Audio gear, Eh? Here's the tools you need...

Discussion in 'DIY' started by EchoWars, Nov 16, 2010.

  1. EchoWars

    EchoWars Hiding in Honduras

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    Got some downtime while waiting for some parts, and since I had made this list for a friend after giving it all a lot of thought, I figured that I might share with you my findings...

    In general, the focus here was to get the best bang for the buck. There are more expensive options, and less expensive options, but I wanted a good balance while keeping a close eye on the total expenditure.

    The raw list consists of (and I will go into detail for each in the next section):
    1. Oscilloscope
    2. Audio Signal Generator (10Hz~100KHz)
    3. Solder station or solder iron
    4. Digital Multimeter(s) and minigrabber leads
    5. Dummy Loads
    6. Dim-Bulb tester
    7. Digital Caliper
    8. Solder
    9. Solder Paste
    10. Solder Wick
    11. Solder Sucker
    12. 170 Side Cutters
    13. Hand Drill & small bit assortment
    14. Machinists Scribe
    15. Bondhus Metric and Standard Ball-End Allen Wrench Set
    16. Helping Hands
    17. Assorted Hand Tools (#1 & #2 Philips, pliers, wire strippers, etc.)

    Let's look at these one by one:

    1. Oscilloscope
    I like to recommend the Tektronix 465B, as Tek sold more of these than pretty much any other scope in history. It is reliable, rugged, repairable, and easy to use, and can be bought in perfect working condition for under $500 ($200~$275 is not uncommon, even for a nice one). There are tons of spare parts around, and any scope repair guy knows this one, if he knows any at all. There are other options, but for someone who simply doesn't know where to start, you won't go wrong here.

    2. Audio Signal Generator
    A tougher one. What I have included here are the inexpensive solutions...there are many more options if money is not an issue for you.

    If you have a computer next to your work area, it's possible to use a software solution. But most computer sound cards (or onboard sound) make poor sine waves (the scope will tell the tale), and the bandwidth is limited. Add to this the difficulty of level control and the possibility of offset issues and I have eliminated this as a serious answer. For a 'new, out-of-the-box' inexpensive stand-alone solution, the Rag/Tag 101 Low Frequency Signal Generator (if URL is dead, try a Google search) is a good deal. Distortion is very good for a sub-$100 solution, and it has good bandwidth (to 1MHz). You'll need a BNC-to-Female RCA, and a Male RCA to Dual Female RCA, plus a couple of IC cables to get it connected, but the ease of using this setup is tough to match. Careful of your purchase source...these are built in China, and not all are designed to be used on US 120VAC.

    Other options include the Tenma 72-505 handheld, also known as the Elenco GF-800 (which is of pretty flimsy construction, and doesn't come close to meeting its published distortion specs, and is nearly as expensive as the Rag/Tag 101), a used B&K 3010 or 3020 (with all the issues that a used piece might entail, and middling distortion specs), the old RCA/VIZ WA-504B (ditto on the used thing), and the venerable Heathkit IG-18 or IG-5218 (double-ditto on the used, with questionable user assembly and ancient transistors tossed in to boot). While these are not the only solutions, they are the most common and easy to acquire for under $100 (typically).

    3. Solder Station or Solder Iron
    A bit easier. I would not consider a iron that was not temp-controlled. I know that a lot of guys use the Weller WLC100, which is temp-adjustable, and have good luck, but in the last couple of years, helping others to get started with soldering, I have come to believe strongly in temp-controlled solder irons. If you're looking for a station, the Hakko 936 is affordable and of world-class quality for well under $100. If you'd rather shave a few bucks off of that, I recommend the Weller WP25. While it is not temp-adjustable, it is temp-controlled at 750°C, and you can replace the heating element with a 30W or a 35W unit if you need a higher temp for some specific task (thus turning it into a WP30 or WP35 iron). For 99% of the things you might be doing with audio gear, the 25W element is the most useful.

    If money is no object, take a look at the Hakko 937 digital or the FM203 dual-port. From personal experience, I have a hard time recommending the Weller WES51 or WESD51. I do like Weller's selection of tips better than Hakko's, but if the iron gives you fits, the tips don't matter much, do they?

    4. Digital Multimeter(s) and Minigrabber Leads
    I recommend a least two meters here...a reasonably inexpensive meter, with an hfe measurement function, and a good True-RMS meter.

    For the 'inexpensive' meter, a cheap Harbor Freight meter should do (but please stay away from those $3.99 and $4.99 jobs). This one has hfe measurement capability, and while it is not autoranging, which is good for the rookies, using it will force the rookie to understand what he's measuring by making them select the proper range. The problem with cheap meters is that they are easy to destroy by dropping, or by connecting it in Ohms mode to a live circuit (a Fluke will simply not give you a proper reading in this case but remain undamaged, and Fluke meters are designed to take a bit of physical abuse as well). If someone knows a cheap autoranging meter with an hfe function for under $30, let me know.

    For the True-RMS meter, right now (11/16/2010), the Fluke 114 or 115 are reasonably priced. If that is too expensive still, take a look at the Triplett 9045. True-RMS, autoranging, capacitance and frequency measurement, and an analog bar graph for under $100.

    The point contact leads shipped with most meters is the cause of more blown amps than I care to count here at AK. Tuck them in a drawer somewhere and forget about them. Here are Pomona Minigrabber leads, and this is what you shall use. Digikey PN 501-1060-ND for 48" black, and 501-1061-ND for 48" red. Every meter you own should have a set of these.

    5. Dummy Loads
    Obviously, we can't use speakers for power testing. There are a lot of options here, but some simple ones are:

    Parts Express 4 and 8 ohm 100W & 200W
    Inexpensive edgewound from Digikey
    More aluminum body resistors from AmpTechTools

    I could put up 100 links to possible solutions. Personally, I use the two 4 ohm 200W aluminum type from Parts Express for each channel (looks like AmpTechTools sells the same 200-watters for cheaper). Bench testing should be limited to 8-ohm loads, unless a specific procedure in the service manual calls for a 4-ohm load (and many do, so you need to have that capability).

    6. Dim-Bulb Tester
    Tons of posts here at AK about them, so this isn't the place if you want to learn how to build one. But basically it is simply an incandescent lamp fixture in series with an outlet as a means of limiting the current to a piece of equipment of unknown health. The fixture allows you to change the lamp to vary the current limiting capacity depending on your needs. For preamps and small (<25WPC) amps & receivers, a 25W or 40W bulb. For integrated and medium sized amps (30W~60WPC), a 60W bulb. For 70WPC to 160WPC, a 100W lamp for most occasions, and for the biggest amps (200WPC and more), a 200W lamp.

    7. Digital Caliper
    Indispensable, especially when replacing caps and trying to figure out what will fit where. Also (and this is a trick I'll give away here once and once only), a little set of 3" or 4" calipers can be used to measure the component hole spacing on the PC board, and then used to bend the leads perfectly for a drop-in fit. The alternative is something like this, which involves too much guesswork for my tastes.

    8. Solder
    Yep, you need solder. I use Kester "44" rosin core, 60/40 in a .031" diameter. Used it for 30+ years, and I have no intention of changing now. I suggest you use it too.

    A nice addition here is a dispenser for 1/2 and 1lb rolls of solder, like this one from Parts Express. Saves a lot of trouble in the long run.

    9. Solder Paste
    Yes, the solder has rosin in its core. But with the small size solder I use, the rosin burns up pretty fast. Plus, I like perfect-looking solder joints, so I use solder paste on 99% of all my solder connections. I have a machinists scribe that I use to scrape a tiny bit of paste from the can and smear it onto the connection to be soldered. The paste helps the heat flow fast and evenly, and makes for a perfect connection every time. Cleanup the excess with a Q-Tip and acetone.

    Kester used to have a paste called 'SP-44', but is has apparently been discontinued. The easiest replacement is from Radio Shack...stock number 64-022. I wondered how they managed to keep it on the shelf without refrigeration till I bought some and saw that it had a sort of 'safety-seal' to keep it fresh. Anyone here knows that I'm not big on RatShack stuff, but this flux works just fine, and you can buy it locally (most online places will insist on overnight shipping for flux products so they can be properly stored). Keep the lid on your flux paste and store it in the fridge when you're not using it. Don't ask, just do it.

    10. Solder Wick/Braid
    Even though I have a fancy desoldering station now, I still need solder wick. Desoldering without destroying foil traces is an art form, and solder wick is part of the equation in getting it right. I will warn you that some solder braids are totally useless...and as copper is getting expensive, it is tempting to cut corners by buying the cheap stuff. I use Easy Braid One-Step No Clean, in a 0.100 width, from Digikey. EB1057-ND

    11. Solder Sucker
    The de-facto standard is the Edsyn Soldapullt (link). I had one for years until it finally irreparably broke. Since then, I've been using a cheapie from All Electronics. They do not stock the replacement tips for the unit, but Apogee Kits apparently has tips that will fit (#BITVTD5...I have some, and they work fine).

    Many AK'ers swear by this gadget from Radio Shack (cat #64-2060 if the link goes bad). I have never used it, so I can't comment other than to say that I see no reason that it should not work fine, but at 45W you need to limit your time on the PC board...that tip has to be at 875°F or more.

    12. 170 Side Cutters
    Why 170? I dunno...they don't measure 170-anything in any dimension that I know of, but yet 170 cutters are an industry standard, and nearly every electronics tool maker has a version or two. Here's a version from Swanstrom Tools at Digikey (#232-1025-ND).

    13. Hand Drill/Precision Drill Set
    Need something to clean out a hole in a PC board? Here's a 21 piece set from Hobby Tool Supply. I believe Harbor Freight also sells something similar, as your local hobby shop may do as well.

    14. Machinists Scribe
    One of the tools that, if I didn't already have one, I'd have to go buy one. Harbor Freight has a two-piece set that is great. Link.

    15. Bondhus Metric and Standard Ball-End Allen Wrench Set
    You're gonna need these. Trust me.

    16. Helping Hands
    These. Cheesy little bastids, but they have their use.

    17. Assorted Hand Tools (#1 & #2 Philips, pliers, wire strippers, etc.)
    Jewelers screwdrivers, X-Acto knife with lots of spare blades, various metric and SAE sockets (1/4" drive for most electronic work). There's always something, but the core tools you'll need here are the #1 and #2 Philips, slip-joint pliers, 4" needle-nose pliers, and wire strippers (I recommend this type for rookies and pro's alike).

    I might add things as I think of them, but for the time being, this is a good start. I do not declare that this is THE definitive list, and that there are not other options. But I will say that a lot of thought went into the choices here, and you may take them or leave them as you see fit...I do not intend to start a mud fight over my selections and I do not want to spend 3 pages of posts defending them...BUT, if you have constructive criticism to add, or other options that I have not included, you are welcome, nay, encouraged to add your thoughts.
     
    Last edited: Mar 12, 2011
  2. Dmannnnn

    Dmannnnn Up Late

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    What are the top five reasons for me to get an o-scope for audio repair? What are its most common uses?
     
  3. Jailtime

    Jailtime Standin' on a corner

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    Wanna do some testing to find out how much power your amp develops into an 8 (or 4 or 16) ohm load? Gotta have a scope. Wanna check if your amp has oscillation issues? How about tracing a signal back to find a source of distortion your amp may have? Learn to use a scope (good tutorials at Tektronix website), and its uses are endless.


    And a few things from my experience I'd like to add to EW's excellent list. If you really want to go whole hog on the test equipment, you'll want a distortion analyzer.

    I use a Tek 2246 scope myself, but I don't think you could go wrong with a Tek 2236. They are bulletproof, the USAF has been using them forever down at Keesler AFB for electronic principles. Been in use pretty much every day for 20 years.

    As far as the soldering station, I use a Weller WES51. The tips are indeed great, but the unit seems a bit flaky. I'll see the little flashing light shut off sometimes. Hasn't let me down yet, but I'd expect a bit better quality from a $100 unit.

    A big +1 on quality minigrabber leads. Ever tried to hold those pointy leads with one hand? You're asking for a blown amp. Grabbers leave both your hands free. And just stop making excuses, get a Fluke DMM. I'd recommend a 179.

    I use Kester "44" 63/37 solder. I 'spose is a matter of preference. I like the eutectic solder because it sets fast. Handy for those tough to reach spots. I've had good experiences with Tech Spray solder wick too. Stuff isn't cheap though.

    For the price, I don't think you can go wrong with the Parts Express dummy loads.
     
  4. EchoWars

    EchoWars Hiding in Honduras

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    As I stated in the beginning, this list is the bare-bones...a starter kit, if you will, attempting to keep total costs to about $750 or less. Adding distortion measurements is going to more than double that total, since you'll need a low distortion signal source as well.

    FYI, my main scope is a Tek 2236. Again, I managed to get a great deal on it. But if it went belly-up I'd probably go shopping for a 465 or 475.

    Edit: Since I can't edit the original post (max post size has changed since then), I'll add a few notes here:

    New AmpTech Tools link: http://www.tedweber.com/amptechtools/dummy-loads
    Hand Drill Set: Do a Google search for 'Pin Vice Drill'.
    Audio Signal Generator: I've since learned that Kenwood has been making a pretty decent little oscillator for several decades, the Kenwood AG-203 (there are 203A, B, C, and D variants as newer models came out). Google it and you should find some sources.
     
    Last edited: May 20, 2015
    Oscar23 likes this.
  5. Jailtime

    Jailtime Standin' on a corner

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    Yeah, I 'spose that the distortion analyzer is well beyond something that the average hobbyist would need. Now, if you're going to restore a large volume of amplifiers in an attempt to make a profit, you could justify the cost. I guess one can always go overboard, and get something like the Pace/MBT desoldering station at my shop. Now I see why you're going bare bones here, 'cause no one wants to spend 2K on equipment to bring a few amps up to snuff.
     
    sunrayjack12 likes this.
  6. Cadillac Kid

    Cadillac Kid Addicted Member

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    Great post, thanks. I also have the Tek 2236.
     
  7. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Another absolutely CRACKING good post from EW.

    Thank you Glenn :thmbsp:
     
  8. gyrene

    gyrene No Marconi:Gomer MacGyver

    Nice thread but I got distracted by Jailtimes avatar...black and white photos have that vintage look...so...cool.
    So Jailtime...who's the babe?
    I don't recognize her...
     
    sunrayjack12 likes this.
  9. Overundr1

    Overundr1 AK Subscriber Subscriber

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    Thanks for posting this up EW. Might I suggest adding JIS #0 and #1 4" screwdrivers to the list? They really help in preventing turnout of those natty glued down gorilla tightened screws and are inexpensive to boot. Most hobby stores carry them for rc cars. I run a magnet across mine before use to help me from chasing dropped screws around the bench.
    -Lee
     
  10. Impedance

    Impedance Well-Known Member

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    The first time I took apart a receiver, I used a swiss army knife... clearly I have a lot to learn.
     
  11. SPL db

    SPL db It's all about the music! Subscriber

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    Got "all the above" and more. :yes:

    Very good list Glenn. :thmbsp:

    Scott
     
  12. awise1961

    awise1961 Super Member

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    This is great stuff guys!

    I picked up a TEK 7603 scope and cart a couple of months ago that I am learning to use. I have the cart figured out pretty well, it's the scope that's the challenge.

    Al. Wise
     
  13. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Grace Kelly
     
  14. gyrene

    gyrene No Marconi:Gomer MacGyver

    Oh man...how could I have missed her...great choice.
     
  15. bigdirty

    bigdirty High fidelity brah

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    Great post, thanks Echowars. vote for sticky
     
  16. Dayum! Being a newbie to AK and enviously viewing endless pics of listening spaces, I'm quickly learning how truly ignorant I am to the world of Vintage Hi-Fi.

    EchoWars,
    Thanks for the list of essentials for Audio Gear Repair. But I have a question, is there a book, or better yet a DVD, on Soldering for Dummies out there - cause, I SUCK at soldering! And something tells me that I need to get good at it if I want to collect/repair vintage hi-fi.

    Thanks...NTD
     
    Last edited: Nov 17, 2010
  17. Fisherdude

    Fisherdude Regular Dude - Super Mod Super Mod Subscriber

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    Do a YouTube search on "soldering". There are many excellent videos that walk you through all the steps, even including SMT component soldering. This will get you started:

    http://www.youtube.com/results?search_query=how+to+solder+electronics&aq=8
     
  18. day67

    day67 Super Member

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    .....Agree on the Helping Hands tool. I've looked and looked for a better, actually a larger one. Anyone come up with a less "cheezy" alternative??
     
  19. BruceRPA

    BruceRPA AK Subscriber Subscriber

    Bravo! Well done! There is nothing quite like learning from the experiences of the master.

    Thank you Glenn! :thmbsp:
     
  20. RossW

    RossW AK Subscriber Subscriber

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    A few additions I would make:

    - A good light source, it's hard to troubleshoot and repair if you're squinting in dim light, a flashlight is also helpful
    - Hemostats, easier than pliers for complex tasks because they're smaller and latch unto whatever you're holding
    - Heatsink grease, I prefer non-silicone electrically insulating personally
    - Heatshrink assortment, lower importance but still handy to have around, especially for point to point wiring in older gear
    - Bleeder resistor for PS caps, 50kohm 5watt is a good general purpose resistor for SS and tube work up to 500V.
     
    Last edited: Nov 17, 2010

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