Thanks for pointing that out WOW yeah that could be bad 

I'm gonna go ahead and say that's a big fault them having it that way 

Also what if you guys were having me probe transistor leads and I kept reporting backassward results   

I can't say I'm over the moon with the auto range meter probably a dumb decision to try one  I don't like sitting there watching it think 

In other news I'm finding im gonna have to have a big come to Jesus about conventional current vs electron flow   

It's pretty uncommon to see reverse polarity on ohms function like that, but there is nothing official about how it has to be done.
I would check the polarity of the Capacitance function on that HD160 meter as well.  In the instructions, it describes how to attach the probes one way, but then has a picture showing it the other way.  You don't want to apply reverse polarity to a polarized capacitor.

I meant to follow up on this but got busy and forgot. I ended up changing the opamp out and it all worked perfectly. The input section had failed and the output worked.

It's a really nice sounding spring reverb. Really a nice amp all around. There were further issues, the weird effect loop selector switch was flaky. Every time I played a low note the vibration would cause that switch to make noise. I thought it might be a tube at first, but I had spares enough to prove that incorrect. It looks like a pain to change out or even jumper, so I'm just not touching it for now.

Thanks to everyone for the help. This forum is great, nice community of helpful people.

It all depends on what you're looking for.  To get you started, here's a few (fairly) easy entry suggestions -

Overdrive: Ibanez TubeScreamer. Look for the stripped-down version that focuses on just the audio processing circuit and leaves out the switching.
Distortion: You can't beat the Boss DS-1; classic and lots of pedals are either clones or tweaks of this original design.
Chorus/delay: Look at projects that use the PT2399 chip.  They have been discontinued recently, but are still widely available.
Fuzz: Try a Fuzz Face.  Classic and easy to tweak for different sounds.

f you don't want to go for a kit, there are a couple of alternatives that get your feet wet without diving into making your own PCBs -
 
Tagboard Effects:
https://tagboardeffects.blogspot.com/
Tagboard is a pre-configured board with strips of copper and pre-drilled component holes.  By cutting through the strips at strategic places, you can make complex boards.  This guy has a bunch already laid out with pictures and tagboard cut diagrams.  Mostly easy, just follow the diagrams and supply your own box.

Effects Layouts:
https://effectslayouts.blogspot.com/
Lots of perfboard layouts and PCB designs in case you want to get into that.  Schematics he usually refers to FreeStompBoxes.org.  Check out his "General Layout Notes" section, lots of easy diagrams for planning connections inside the box.

Hope this helps!

The diode testing mode is showing 601 mV.  It's a good diode with a reasonable forward drop.

These meters work by putting out some known, fixed current into the device and measuring the voltage. That current is going to be tiny! Remember that silicon diodces have a nominal forward drop of 0.7V; but the detailed model is that they start conducting at significantly below that, at small currents. That's why you can get readings below 600 mV for diodes.

Measuring ohms is a crapshoot. Multimeters measure resistance also by putting out a fixed current and measuring the voltage. The current used varies with the range: like millamp-level currents for the smallest ranges, and down into hundreds of nanonamperes for the biggest range.

Let's say that your multimeter is using a 100 nA test current for the multi-megohm range. The voltage drop would be 0.1V across a 1M resistor.   The voltage across a diode conducting 100 nA could also be 0.1V, so that it reads as a 1M resistor. With a forward bias of 0.1V, it's possible for a diode to be conducting 100 nA.

Try this diode current calculator: https://www.everythingpe.com/calculators/diode-current-calculator

You can't pick a diode from a list here, needing to know the saturation current. This is like 2 to 4 nA for a 1N4148, so let's use, oh, 2.5 nA.  Then we put in a voltage of 0.1 and hit calculate. The current is 1.1E-07A, which is 110 nA. So that checks out.

But actually, 3.3 MΩ was observed on saturated's auto-ranging meter.  Can we use that to guess at approximately what current it is using for probing the component?

Yes! The meter is using around 20 nA.   At that value, a 3.3M resistor drops a voltage of 0.06V.  And 20 nA is in the ballpark of the forward current through a diode at 0.06V.

I now see that this perceived "problem" is mere child's play for the Mighty G1 

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Set the Ideal or the Centech to measure DC volts.
Check the polarity (and voltage) of the DC being put out by the Amprobe's when they are set to ohms or diode check functions.

@electrucio: for your comprehensive list, maybe of interest (some entries may be already existing):

• Power and Grounding for Audio and Video Systems - A White Paper for the Real World – International Version, Jim Brown, Audio Systems Group, Inc.
• RaneNote, PIN 1 REVISITED
• So You Thought Your Amplifier Was Balanced? No matter what the advertising or manual says it probably isn't! http://www.audionote.co.uk/articles/art_balanced.shtml
• A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing, by Jim Brown K9YC, Audio Systems Group, Inc.,http://audiosystemsgroup.com
• Jensen AN-004, HUM & BUZZ IN UNBALANCED INTERCONNECT SYSTEMS,by Bill Whitlock
• Ground and (safety) Earth, by Eric Juaneda, January 2008,http://tech.juaneda.com/
• Audio Component Grounding and Interconnection, Dave Davenport

this is not an easy subject.

I went back and rechecked all my results and even added a couple other multimeters to the mix

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Gonna have to think about this one for a while 

A baffling experience was recorded today 

Using a multimeter where you have to select the range the resistance of a forward biased diode was about 3.3 Mohm and infinite reverse biased
Then using the diode function the typical forward voltage drop was obtained without incident.

So what's the beef  well the auto ranging multimeter showed infinite resistance when forward biased and a few megohm when reverse biased  (and it has no diode test function)