Suggestions for building up a toolkit for testing?

[tonedef]

Hi all! I've got a 50/50 success ratio in my builds. Kits I do well, my own designs and from schematics, not so much. Trying to figure out a practical toolkit to debug a plethora of issues (I mostly do high gain stuff).

My current test kit is:
Oscilloscope
Cheap multimeter
Signal generator
Dummy load

Thinking to add:
US made Variac + isolation transformer
Ammeter (suggestions? Kyoritsu 2300R, Fluke iFlex?)
Tube tester (suggestions?)
Guitar looper
Breadboard (will build one like silvergun's awesome SOAB)
Listening amp

Any other go-to tools people use?

[shooter]

the tool list is fine, although much will go unused once you develop an attention to detail, so you don't have to find problems you created.
here's a simple list
ohm EVERY resistor prior to placing it on the board.
use a magnifying glass to verify where the zeros are on caps.
trace each turret you are about to use "backNfwd" to their destinations, verifying they are the correct turrets.


that takes care of 80% , the other 20% is typically "on the schematic" that got miss-interrupted 

[PRR]

Nevermind the hardware. The important tool is between your ears. And it needs all the help it can get.

If they "don't work", it may not be all solder joints or cap values. It's not connected right. "If it was, it would be working by now."

How to double check your amp wiring and find things you missed
https://el34world.com/Forum/index.php?topic=17701.0

[tdvt]

ohm EVERY resistor prior to placing it on the board.
use a magnifying glass to verify where the zeros are on caps

I bought one of these (different brand, looks identical) a while ago;  LCR-T4 Digital Tester  for this very reason. I have a couple of alligator leads connected to the test socket & I check every component as it goes on to the board.

5 seconds to test a component. No changing settings, it recognizes whatever you connect, tells you what it is & the value.

This was some of the best spent $ towards minimizing errors as it is so quick & easy to use.
As for the other stuff, I agree with the previous advice in that much/most won't be used as you gain experience. I will confess to starting a listening amp probe myself....

[acheld]

+4 on that cheap tester!  it's great for what it is.