Results 1 to 19 of 19

Thread: Sholud I get more diagnostic tools?

  1. #1
    Supporting Member mtlbasslad's Avatar
    Join Date
    May 2010
    Location
    Rawdon, Quebec, Canada
    Posts
    126
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0

    Sholud I get more diagnostic tools?

    Hi all - well the title says it all - should I?

    After my last adventure into a Marshall 6100 I was frightened by all the boards, IC's, ribbon cables etc... a long way from point to point Fenders...

    I thought maybe a signal generator would remove the need to borrow my wife's Strat & keep strumming while I tried to figure out what was going on in the amp - there are cheap ones on Amazon under $100 - so I ordered one

    Now of course I'm looking at cheap ($250) digital oscilliscopes - could a noob like me really use these tools?

    The only really quality tool I have is my new Fluke multimeter - and you guys

    Your opinions welcomed

    Cheers, Lorne

    PS - the Marshall 6100 will be onstage tonight - let's hope no 'magic smoke' appears

    0 Not allowed! Not allowed!
    I'm not old - I'm vintage

  2. #2
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,207
    Thumbs Up/Down
    Received: 5/0
    Given: 4/0
    If your goal is to keep repairing amplifiers then a signal generator is a must.

    A scope is a plus as you can actually see the waveform.

    I would add a Kill-A-Watt meter to the list.

    0 Not allowed! Not allowed!

  3. #3
    don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    9,836
    Thumbs Up/Down
    Received: 58/0
    Given: 100/0
    I think you mentioned elsewhere people starting to bring you stuff to fix. Get a scope, you'll never regret it.

    0 Not allowed! Not allowed!
    Certified Dotard

  4. #4
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,873
    Thumbs Up/Down
    Received: 77/1
    Given: 0/0
    You don't need a digital scope, though they work too. Any old analog scope will be good enough.

    I use a signal generator for certain things, but for general work, I just run a cable from a CD player and use the music for a test signal.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  5. #5
    Old Timer olddawg's Avatar
    Join Date
    Dec 2007
    Location
    Carlsbad, CA and Kona, HI
    Posts
    2,611
    Thumbs Up/Down
    Received: 8/0
    Given: 0/0
    Or get a signal generator app for your phone...

    0 Not allowed! Not allowed!

  6. #6
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,468
    Thumbs Up/Down
    Received: 14/0
    Given: 13/0
    In order of importance I would choose the following to have as a minimum:
    1) DVM (which you already have)
    2) Signal generator
    3a) Scope
    3b) Dummy load
    4) Variable AC supply ("Variac")
    Those are the basics and there are many advanced instruments that are nice to have such as spectrum analyzers,tube testers, transistor testers and more. However, the best is to develop a good understanding of how circuits operate and practical troubleshooting skills coupled with a good thinking to filter out the BS mojo that floats thru the internet and the books published by self appointed gurus.
    R,
    Tom

    0 Not allowed! Not allowed!

  7. #7
    Supporting Member
    Join Date
    Dec 2009
    Location
    UK
    Posts
    3,250
    Thumbs Up/Down
    Received: 12/0
    Given: 2/0
    For a test signal I mainly use a single-transistor 1khz sine oscillator I built in the 70s and is still going strong. It just has an output level control and on-off switch. I have that to hand all the time. For bass and PA amps I have a simple hand-held signal generator.

    0 Not allowed! Not allowed!

  8. #8
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Location
    Chicago, USA
    Posts
    4,908
    Thumbs Up/Down
    Received: 37/0
    Given: 0/0
    Quote Originally Posted by Tom Phillips View Post
    In order of importance I would choose the following to have as a minimum:
    1) DVM (which you already have)
    2) Signal generator
    3a) Scope
    3b) Dummy load
    4) Variable AC supply ("Variac")
    Those are the basics and there are many advanced instruments that are nice to have such as spectrum analyzers,tube testers, transistor testers and more. However, the best is to develop a good understanding of how circuits operate and practical troubleshooting skills coupled with a good thinking to filter out the BS mojo that floats thru the internet and the books published by self appointed gurus.
    R,
    Tom
    5) Light bulb limiter.
    6) Isolation transformer.

    0 Not allowed! Not allowed!
    "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

  9. #9
    Senior Member
    Join Date
    Jun 2006
    Posts
    426
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Relatively cheap and useful items:

    Bleeder resistor with rubber-covered alligator-clip leads to drain capacitors on unplugged units.

    Chopsticks, to poke around inside a live chassis flexing wires, etc., tapping on tubes, and eating Kung Pao chicken while you ponder the problem.

    Advil, for when what you pondered while eating your Kung Pao doesn't work.

    Contact cleaner, like De-Oxit.

    Assuming you already have a good soldering rig?

    A tube tester might come in handy to get a general idea about tube health, and strength?

    Brad1

    0 Not allowed! Not allowed!

  10. #10
    Better Tone thru Mathematics bob p's Avatar
    Join Date
    May 2006
    Location
    Chicago, USA
    Posts
    4,908
    Thumbs Up/Down
    Received: 37/0
    Given: 0/0
    ^ A good soldering station, or a reworking station, is going to be an essential piece of gear if you plan on working on PCB equipment. If you plan on working only on turret boards and eyelet boards then you can get by with a cheap low-watt soldering iron, a heavy-duty soldering iron and a soldering gun.

    0 Not allowed! Not allowed!
    "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

  11. #11
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    29,873
    Thumbs Up/Down
    Received: 77/1
    Given: 0/0
    Agree with all the above.

    I think technique is more important than having a ton of gear. In my pro shop, the vast majority of work is done with meter in hand. My scope is always running so I can reach for it. Learn what you are looking for in the amp. I can check ripple with my meter, with my scope, with a signal tracer. The important thing there is knowing what ripple is and where it comes from.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  12. #12
    Senior Member jbltwin1's Avatar
    Join Date
    Nov 2008
    Posts
    240
    Thumbs Up/Down
    Received: 3/0
    Given: 0/0
    Check ebay for some of this stuff. I bought a LIKE NEW sig gen for 20.00 to replace my 50 year old one that was as big as a car. My scope is an old school scope from the 60's. Works just fine for audio unless you need dual trace. A good audio probe is handy too, if you either have a spare amp or an old audio tracer amp like mine. THAT is also probably 50 years old that is on my bench. A good ESR meter is great for finding crap caps. I have an old Eico electrolytic cap checker that ALSO still works like a charm and it's even older. Maybe 50's? Mike.

    0 Not allowed! Not allowed!

  13. #13
    Supporting Member
    Join Date
    Dec 2009
    Location
    UK
    Posts
    3,250
    Thumbs Up/Down
    Received: 12/0
    Given: 2/0
    Quote Originally Posted by Enzo View Post
    I think technique is more important than having a ton of gear.
    Technique and experience are the keys to effective troubleshooting. Reminds me of the phrase "All the gear, no idea". No amount of test gear makes up for poor technique. It's worthwhile studying repair techniques - how to track down a fault quickly and effectively by observation and understanding. There's a certain feeling you get when you identify a defective part, replace it and fix a problem. There's no satisfaction whatsoever in replacing good parts and making no difference, or introducing new problems.

    Simple techniques can overcome lack of equipment. I remember Enzo describing using a DMM and diode to see if half a waveform was missing - the guy didn't have a scope. A friend had a problem with his fuel-injected bike. He started looking at expensive diagnostic equipment. I used a DMM plus grain-of-wheat lamp soldered to some clip leads and sorted his problem out in 15 minutes.

    There are some good references to technique - Jack Darr's books, the Tektronix scope troubleshooting handbook etc. It doesn't particularly matter which field of electronics - its the techniques you're looking for.

    0 Not allowed! Not allowed!

  14. #14
    Supporting Member mtlbasslad's Avatar
    Join Date
    May 2010
    Location
    Rawdon, Quebec, Canada
    Posts
    126
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks for all your replies - good advice as always.

    Here is what I had on hand before asking the question:

    Fluke 115 (measures capacitance & is auto-ranging, YAY)
    Weller WES51 soldering station (gift from child, more YAY) along with solder pump, de-soldering braid
    Light bulb limiter I built last year on advice from y'all
    Dummy load is an 8 ohm speaker...
    Helping hands gadget, heat sink paste, heatshrink, hooks & pics assortment, Deoxit, freeze spray...
    And chopsticks !

    Now I have a Kuman FY2202SP signal generator & a Hantek DSO5072P oscilliscope on the way... still looking at a 3 amp variac...

    And the best advice I got from you all is of course to try & know what i'm doing. To that end I have asked my child to loan me the book I bought him when he was 12 - and I will read it.

    I like to think I have good analytical skills coming from 15 years of programming mainframes - as in follow the signal path.
    And keep one hand in my pocket LOL

    No doubt I'll be needing your collective help when the new toys arrive, wish me luck!

    Thanks, Lorne

    P.S. Next project is a 50's Silvertone 1432 rescued from an abandoned building - got it working except for the tremolo, clusterf*%k of caps & resistors around the 6AU6 tube...

    OOPS, forgot the venerable Knight 600 tube tester, for what it's worth...

    0 Not allowed! Not allowed!
    I'm not old - I'm vintage

  15. #15
    Supporting Member mtlbasslad's Avatar
    Join Date
    May 2010
    Location
    Rawdon, Quebec, Canada
    Posts
    126
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Postscript to this thread...

    Would a 500VA (.5KVA) Variac be big enough for my needs here? It's $90CDN with free delivery - everything else delivery is as much as the cost... ??

    0 Not allowed! Not allowed!
    I'm not old - I'm vintage

  16. #16
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,468
    Thumbs Up/Down
    Received: 14/0
    Given: 13/0
    Quote Originally Posted by mtlbasslad View Post
    ...Would a 500VA (.5KVA) Variac be big enough for my needs here? ...
    If you are talking about up to medium power amps, i.e. up to around 150 W output power then a 500VA Variac will be OK. If you plan to work on high power amps such as SVTs, big SS Bass rigs or sound reinforcement power amps then you will need a variable AC transformer of a larger rating.
    Tom

    0 Not allowed! Not allowed!

  17. #17
    Supporting Member mtlbasslad's Avatar
    Join Date
    May 2010
    Location
    Rawdon, Quebec, Canada
    Posts
    126
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Thanks Tom, last amp I worked on (Marshall 6100) is only 100W - the one on my bench now (Silvertone 1432) way less.

    Hope my neighbor with the Mesa Carbine-or-something never has problems with that amp - tick,tick,tick LOL

    I thought VA rating was straightforward, seems not so - AC or DC etc. The Variac I'm looking at has the usual conflicting specs - 5 amp or 3.7 amp... it's on fleabay 'Canadian shipping' the usual China stuff but shipped from Canada (they say). Lots of nice stuff out there but most vendors treat Canada like a 3rd world country - $10 thing = $50 shipping, ARRGH

    Guess I'll go for this one - thanks again for your input

    Lorne

    0 Not allowed! Not allowed!
    I'm not old - I'm vintage

  18. #18
    Old Timer Tom Phillips's Avatar
    Join Date
    Jun 2006
    Location
    California, USA
    Posts
    3,468
    Thumbs Up/Down
    Received: 14/0
    Given: 13/0
    An additional thing to consider is that the most useful bench variacs are the ones that have built-in voltage and current meters. Since variacs certainly aren't rare there will be lots of opportunities to buy them and you may want to consider holding out for one with meters. It's nice to get a good deal but it's even better to have the more complete capability for your bench setup which you will use over and over again.

    0 Not allowed! Not allowed!

  19. #19
    Supporting Member mtlbasslad's Avatar
    Join Date
    May 2010
    Location
    Rawdon, Quebec, Canada
    Posts
    126
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Signal generator arrived & seems to work OK - just having trouble understanding the 'Chinglish' manual...

    Scope should be here soon, birthday present from best wife ever. Then I just have to learn how to use it - I suppose the manual will be in 'Chinglish' too...

    0 Not allowed! Not allowed!
    I'm not old - I'm vintage

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Useful tools
    By Enzo in forum Music Electronics
    Replies: 141
    Last Post: 09-15-2017, 02:06 PM
  2. UV diagnostic
    By gbono in forum Maintenance, Troubleshooting & Repair
    Replies: 0
    Last Post: 05-28-2016, 04:54 PM
  3. Tools of the trade...
    By Steve A. in forum Lobby
    Replies: 15
    Last Post: 06-23-2014, 10:03 PM
  4. Appreciat Diagnostic Help for Old Roland Orange Cube-60 Guitar Amp
    By mikelazich in forum Maintenance, Troubleshooting & Repair
    Replies: 16
    Last Post: 04-20-2011, 10:09 AM
  5. 3-way hi-fi speaker diagnostic, please
    By Don Moose in forum Music Electronics
    Replies: 5
    Last Post: 01-29-2009, 12:49 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •