Quote from: guitarboomer88 on March 15, 2014, 07:20:34 PM
I never noticed the hum before I tried to record with no load...

That was probably the first time you ever had it running without speakers, so you had never heard it dead quiet before.
Now you will never be able to "un-hear" the quiet, no speaker sound 

 I'm seeing a "file unavailable" message for the pictures.

Quote from: thehallofshields on March 14, 2014, 05:15:18 AM
However: I measure Infinite Resistance (at the 2mega-ohm setting) between the positive and negative wire of the transformers input. Do you call the Transformers Input the Primary and the Transformers Output the Secondary? Do I have a bad 'primary'?

Yes, the input is the primary, output is secondary.  From your picture, the input is the red and blue wires on the one side of the transformer.  If you are measuring infinite between that red and blue, then the transformer is dead (open primary).

  It sounds like the white and black are reversed at the switch.
Black should connect to brown (to fuse) when switch is turned on, white should connect via switch to blue.
  The orange wire may be the transformer case, which is shown on the schematic as connecting to the green earth wire of the mains.

  With some pictures and transformer primary resistance readings, it should be easy to bypass the voltage selector switch for test purposes,  or hard wire for 120V operation.

  Along with resoldering the tube sockets like Dr.Gonz suggested, I would also suggest resoldering the main filter caps and the 2 power resistors in the low voltage power supply.
The power supply is the only thing really common to both the preamp and the power amp, so if indeed the problem is in both sections, the power supply could be the culprit. 
The only other thing common to both is the speaker.
But you said the clean channel is fine.  If the clean channel is fine, then going straight in to the power amp should also be fine.
Do more testing to see if the problem occurs when straight in to the power amp or when using the clean channel.

  Don't connect your black probe to neutral, connect it to the chassis (ground).
Is it a three prong plug and is it wired correctly?
Don't worry about the pilot lamp if it is turning on and off with the power switch, as long as one side of the lamp is switched (hot side) you should be ok.
  Is the voltage selector set correctly?
  The caps that look bad may need to be replaced with higher voltage versions due to the increase in modern line voltage.
The diode etc. off the bridge may be a revised bias arrangement.  Leave it in place till you have drawn it out and know what is going on with the circuit.
You have a dim pilot lamp, what is the AC across the PT primary and PT secondary (into the bridge) ?

Quote from: joshdfrazier on March 10, 2014, 08:21:13 PM
the same thing happened, taking out the output transistors. Keep in mind I did this awhile back, before I had any experience with solid state gear

If you didn't have any experience at that point, can you be sure the output transistors were bad?  I think you should drop that assumption if they are currently measuring ok.

  There is no such thing as a "higher gain" version of a 4558 that is still labelled as 4558.  They are all high gain.  A version with a different gain would not be a 4558 anymore.  There is an upgraded version, 4559, then 4560, maybe more.
  If you can find a DD for sale, and they offer a datasheet, it is the standard 4558 or 4558D datasheet.
The Banzai info. is incorrect.

  Would a class D power amp not be more efficient?  Wouldn't that translate into more power to the load from a given supply?

  It is a stereo chorus amp.  The voicing switches should make a difference, maybe not huge though.  Some of the amps had a programmable voicing module.
  The owners manual, and voicing program are available on this page:
http://www.deanmarkley.com/Info/LegacyAmps/Docs.shtml

 Just plug a cord into the main in, with or without signal.  This will disconnect the preamp without even having to open the amp.
 

Ok, here is a repost of the schematic.
As Enzo mentioned, the voltage you use should be what is measured across the resistor.  And somehow you are going the wrong way with your decimals.  A 270K resistor is 270,000 not .027 or anything, for calculations use values in ohms.
  So, according to the values on the schematic:
R2 is 2200 ohms.  There is 312V on one end, 303V on the other.  That means 9V across R2.  9V divided by 2200 = .004  That is the current in amps, or can be called 4mA (milliamps).  Do you know the metric system?  It uses a lot of the same abbreviations and makes electronics easier to understand.
  Anyway, we have 4mA of current flowing through R2.
R3 has 71V across it.  It is a 57K resistor.  So 71 divided by 57000 = .001A or 1mA
So what do these numbers do for me?  Well, there is a difference of 3mA.  So some of the current that was flowing through R2 is not flowing through R3.  Where did that 3mA go?  Look at the original drawing and you will see that there is a line from R2/R3 junction to the power tubes.  This is the screen grid.  So that is where the extra 3mA went.  The spice drawing is missing that line so it is a typo.
  So in this case, those numbers helped me find a typo, but generally we use them to see if tubes are drawing proper current etc.
  If you like, figure out the current through R10.  Then, if I tell you that plate current of a tube is pretty much the same as cathode current, you should be able to figure out what the voltage should be across R11.

Quote from: ilyaa on January 24, 2014, 04:00:53 AM
someone did add some components on the underside (its on the top the way its installed) of the preamp board before i bought this amp, so maybe this particular 2n4248 was replaced and left inside to rot. weird, huh?

You said the amp is tough to get the boards out of.  Perhaps they desoldered a bad transistor and had to push it through (rather than remove the board).  Then it may have got stuck somewhere and they couldn't shake it out.
  Is there a circuit board that is solder side up with a 2N4248 mounted to the solder side?
  This is how repairs are sometimes done when it is too difficult to remove the boards.

Please provide more info.  What schematic are those calculations referring to?
What do those numbers represent?  As straight math they do not work out.

  There are no level controls for the loop on that amp.
But most FX units will have input and output level controls.  Try adjusting them, turn up the input and reduce the output level and see if it helps.  Or the opposite, turn down the input and turn up the output.
  Also it there are any -10/+4db level switches, they should be at -10 setting.