attached is the elusive schematic for this version, full page view on page 5 of pdf

  Maybe this will help.  They don't want the pdf posted elsewhere but here is a link to it:
http://www.generalguitargadgets.com/pdf/ggg_ruby.pdf

and some more
http://www.rustybrooks.com/electronics/mouser/kits?kit=rubyamp

http://rubyamp.com/build.html

http://www.instructables.com/community/Ruby-amp-9v-DIY-guitar-amp/

  Could you please do them one at a time and see which was the problem?  That way we will have a definitive solution to the issue, which may come up again.

  Measure the resistance across D4 (regulator input) and C18 (regulator output).

  I think he was looking at the schematic from the Randall thread, I don't see a 33V zener here.

  The standby switch problem stops the amp from working at all, so that is not your problem.
  If you have a tube that is not lit up, replace it.

  Sounds like it may be breaking into oscillation, causing volume loss and turning on the LED?

Quote from: gbono on September 02, 2014, 07:12:16 PM
When I lift R63 on the -9V supply I get -9V at ZD5 - someting is loading down the supply - but what?

Try the same check with R14 and R23, should help isolate the problem a bit more.

  Sorry, I seem to have messed up with my interpretation of "breadboard".  I was thinking you meant perfboard (vero or strip board) like the picture Roly posted.
  The radio shack breadboard you have is what I call "protoboard" and is not suitable for a permanent installation (and way more expensive).

Breadboard can be used for prototyping or building.  As this is a one off project you can use the breadboard as the finished product.  If you decide you want to go into production, it would be easier to use printed circuit boards.

The 386 suffix denotes how much voltage the IC can withstand, any version is good for at least 9V, so you don't need to worry about it.

Fuses are optional.  You can't hurt yourself with a 9V battery (unless you really wanted to, and connect wires to it that you pierce your skin with).

  It's hard to believe how hot some of these things run "normally".  But you said it was smoking, which it should not.
  The voltage at the zener will tell you.  If you have 33V there, then the heat is the normal amount.  If there is a fault, you will not have 33V at the zener, but some lower voltage.  (this is assuming the other end of R1 has it's proper approx. 45V)

  So R1 should have 45V at one end and 33V at the other, for a voltage drop of 12V.
With a 330 ohm for R1, it would be running about 1/2W.  So the heat there is probably normal if you have 33V at the zener.
Time to get back to proper troubleshooting of the actual fault.

What is the voltage at the junction of R1 and the zener?

Quote from: TolerBear on August 28, 2014, 01:24:04 PM
There's 2 7832 regulators and 1 7831. .

I think you mean two TIP32 and a TIP31.  Then the 4th device on those individual heatsinks can be seen in the pics as a 7824 regulator.
  So perhaps it is a 33V zener limiting the input voltage to the 7824.

Edit:  looking again at the schematic tolerbear linked: http://spaceryerson.com/pics/RG80-Schematic-1.jpg  it appears to be correct, just missing values.

Quote from: TolerBear on August 25, 2014, 03:37:05 PM

This is the original resistor?  What value did you replace it with?  From the other picture it looks like you installed a 300 ohm?
  I guess it's possible it was a 3.3K ohm, or maybe there is a fault causing the overheating.
  Because of the cap near it that does not have a pair, I'm guessing this is the 24V supply, not the + or - 12V.
  Can you read the numbers off D4?  Looks like 1N47 something, need 2 more digits.

Edit:  I don't know what I did wrong with that quote, just click where it says "quote from..." and it will take you to the pic.

  Yes, the link from reply #37 is working and there are pics there.  Click on the main pic and it sends you to the rest.

Are any of them showing the original discolored resistor you are trying to figure out the value of?