Multimeter MEGA tutorial |Theory & Technique for Audio Troubleshooting

I intended to make a short tutorial, but somehow it grew into this 80 minute monster which covers;-

-Which digital multi meter functions I use a lot and which I never use

-What to look for if you're buying a DMM & which accessories I use

A primer on electrical theory suitable for beginners who just want to fix stuff

-Situations where other diagnotic tools are more appropriate than a DMM, and why

-Practical examples of how I use the multimeter in my work refurbishing Portastudios

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TETRAKAN - Fix & Use Tape Recorders

Overviews; tear-downs; repair vlogs; techniques; tutorials; demo recordings...
...covering every cassette multitrack recorder ever made!*
*(eventually)
   / tetrakan  


I post exclusive content on PATREON;-
  / tetrakan  

DONATIONS are gratefully accepted via my BLOG, which also features written articles and FREE DOWNLOADS OF SERVICE MANUALS;-
https://tetrakansupermonobloc.home.blog/

I prefer to answer questions in the youtube comments where my answers can help more than one person, but if you need to share photos etc, you can message me via facebook.
  / tetrakan  

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PRODUCT LINKS
I get a small commission, only if you buy a product - this doesn't cost you anything
Clicking one of the links should show you a choice of stores for your region.
My Extech DMM
https://geni.us/tetrakansmeter
Banana to alligator clip cables
https://geni.us/alligatorDMMcables
Assorted dupont cables, includes M-M and F-F
https://geni.us/dupontassortment
Component tester for semiconductors & ESR/capacitance
https://geni.us/componenttester
Affordable Oscilloscope
https://geni.us/littleredscope

How to build your own audio probe...
https://www.coda-effects.com/2015/07/...

Other Tools & equipment I use when repairing portastudios;-
https://kit.co/Tetrakan

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MORE ELECTRICAL THEORY VIDEOS

OHM'S LAW ETC
Here is a typical ohms law tutorial, complete with pointless battery + resistor circuit
   • What Is OHM'S Law ? [Explained in Und...  
Daniel Sullivan's stuff is great becasue it is pitched to technicians;-
   • What are VOLTs, OHMs & AMPs?  
   • What is Voltage Drop?  
Eugene Khutoryansky's 3D videos are great for visualising hard physics concepts;-
   • Electric Potential: Visualizing Volta...  

ELECTRICAL SAFETY
   • Do Volts or Amps Kill You? Voltage, C...  
   • ⚡ "It's not the volts that kill you, ...  
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Here are all the topics & timestamps;-

0:00 Introduction
0:51 Electrical safety
2:21 Connectors & probes I use
4:51 What to look for when shopping, which DMM functions are most important?
8:51 Plugging in probes - how important is polarity?
11:56 Opinion - most theory is NOT presented with the technician in mind
14:25 The difference between AC and DC
17:09 Ohm's Law - thinking of DC like water is helpful, but I don't do calculations
21:03 Parallell circuits & why we test components out of circuit
25:51 Voltage dividers & Ohm's law
29:38 Understanding voltage drop
32:43 How voltage drop impacts DMM use
35:21 Where I put the probes
37:04 Using a schematic to figure out where to put probes
39:00 Why I don't use AC voltage readings when I troubleshoot PSUs
40:15 Why the DMM is unsuitable for analogue signals
41:15 Why I use an audio probe or oscilloscope for audio signals
44:03 DMM vs 'scope for amplifier & bias calibration
45:17 What is a continuity test?
47:32 C.T ex1 - checking faders, switches, pots etc
49:31 C.T ex2 - checking coils... solenoids, relays, inductors, chokes, etc.
50:12 C.T ex3 - checking magnetic heads
50:49 C.T ex4 - cables & PCB traces
52:26 C.T ex5 - circuit ground connections
55:53 DC volts ex1 - is an active component receving power?
59:56 DC volts ex2 - comparing readings on healthy & unhealthy circuits
1:02:20 DC volts ex3 - identify a faulty semiconductor
1:03:36 Just enough semiconductor theory
1:06:27 semiconductors out of circuit with the diode tester
1:08:42 a cheap component tester is easier?
1:10:47 DMM doesn't show me ESR, a component tester does
1:11:13 in practice I just replace small value 'lytic caps
1:11:56 resistor values & why I check them last
1:13:01 Comparing resistances as a diagnostic tool
1:14:02 AC voltage for checking presence of AC bias
1:15:16 AC voltage for playback amp calibration
1:16:47 Safely troubleshoot PSUs with voltage drop & continuity
1:18:24 Frequency counter to check AC bias frequency
1:19:32 Conclusion