As a tech for over 35 years myself , I have grounded these amps , a real tech ALWAYS , finds a way to ground ANY piece of equipment they work or they will wind up DEAD
[/quote]

Well, if you are grounding these kind of amps (widow makers) without using an isolation transformer that is just not safe.  Roly has explained why.
  You said that an isolation transformer is "not absolutely needed".  That is wrong and unsafe.
  Maybe you could explain why you would want to short cut around the safety that an isolation transformer provides?  I'm sure you are aware that such an amp would be illegal to build and sell today due to safety reasons.

Quote from: EDWARDEFFECT1 on August 10, 2013, 03:52:31 PM
i powered up the amp and ran a chord from the Polytone send to a traynor 20 watt amps return and the volume is low.must be a preamp problem.i need to verify the output section the same way as the volume is lower than what i had previously.

Verify the output section by running the send from the Traynor into the return of the Polytone.

  Looking some more, some people have said the N-68X gets quite warm (even with an amp this small) due to the half wave rectification.
  You could try it to see how hot it gets, or use the next size up:
http://www.mouser.com/ProductDetail/Triad-Magnetics/N-77U/?qs=sGAEpiMZZMvwUzoUXIIvydH8%2fj5UF54y5znvSd0cAC0%3d

 Due to this being such a low power consumption amp, the Triad N68X would probably work fine and is cheap.
http://www.mouser.com/ProductDetail/Triad-Magnetics/N-68X/?qs=%2fha2pyFadugi%2fv1eXR%2f0AiEO2zaUAkSRWI2ho6ZXYjA%3d

  It does not have a power transformer so you would need an isolation transformer.
Because it uses a half-wave rectifier you would probably want to use something rated for about twice the power that the amp uses.
  Tubes are 50L6, 12SJ7, and 35Z5.

Quote from: DckTech on June 17, 2013, 10:40:05 PM
Replaced the original "1122" reverb tank with a "P-MOD-4AB3C1C" = best spec I could find to equal original. 

  May I ask where you got your information regarding this? 
"AB" tanks are for tube amps.  Transistor reverb circuits usually use EB or FB for 2nd and 3rd digit of tank number (which indicates input and output impedance of tank).
  I'm not sure if this would cause the volume drop issue, but I certainly wouldn't expect an AB type tank to work properly in your amp.

  The one you mentioned from Mouser is a screw terminal type, so I'll assume the cap does not mount on the circuit board, but has wires going to the screw terminals.
  Most modern caps are smaller than older ones, so the physical size shouldn't be a problem.
But like Enzo said, you don't need to use their odd values, and may end up paying more for them.
3300 is easily close enough, and 80 or 100 volts should be fine.  Also you can use caps with lugs rather than screw terminals and solder the wires to the lugs.
  Here are some UK offerings for 3000 and 3300uf at 80 or 100 volts, both screw and lug terminal types:
http://uk.farnell.com/jsp/search/browse.jsp?N=215573+110020382+110029824+110152057+110202702&No=0&getResults=true&appliedparametrics=true&locale=en_UK&divisionLocale=en_UK&catalogId=&skipManufacturer=false&skipParametricAttributeId=&prevNValues=215573+110020382+110029824&mm=1000002

http://uk.rs-online.com/web/c/passive-components/capacitors/aluminium-capacitors/?sort-by=default&sort-order=default&applied-dimensions=4294463072,%204294465770,4294461468,4294466587&lastAttributeSelectedBlock=4294955811

  Also note that the extra 5.6K resistor at the socket was put there by the factory.  They put it there at that one socket because it cured an oscillation problem.
  So it would be best to leave it alone, otherwise you may cause a problem that could be very difficult to fix for someone else later.

What do you measure on pin5 of power tubes if you set your meter to AC volts?
How about DC volts at output of DB201 (across C210).
Also, resistance from DB201 + pin to ground, and C210 + end to ground.
  Voltages at the transformer will be AC, so 500V DC would not be likely to be coming from the power transformer.
  The 5.6K resistor is a grid stopper, there are probably 3 more for the other tubes but mounted on the circuit board somewhere.
  It's not really important now but may be helpful for finding correct schematic to know whether you have the 5881 or EL34 version.  Are the screen resistors 470ohm or 2.2K ?  (R251 thru R254)

As far as the speaker jacks, from what I recall there are 2 parallel jacks, no internal or external, both just regular.  So it sounds like one works and one does not.  Resistance checks will tell you which one is bad, it may just need resoldering.

  Without modifications to the amp, you will need a battery in the footswitch to run the light.
You can modify your existing footswitch, or you can buy one already made, something like this: http://www.ebay.ca/itm/Voodooman-FootSwitch-1-Button-W-9V-DC-powered-LED-/380503784108

  Your transformer wiring looks correct.
Now you need to find out why it blows the fuse.  That is where the limiter lamp comes in.
Do not connect any speaker to the output until you determine there is no DC voltage on the output wires.
  The speaker may have been fried by a blown power amp and you don't want to ruin another speaker.
  The output devices (Q2 and Q3) should be checked for shorts, and their emitter resistors should be checked for open condition.

  This amp is ok to use with a 4 ohm load, specs are 120W@4ohm, 80W@8ohm
http://www2.randallamplifiers.com/images/stories/manuals/RG100ES-RG80ES-OwnersManual.pdf

So the fault was not caused by using a 4 ohm load.
Whether the fault is the breaker, or the breaker is just doing it's job is something you must determine, as Roly mentioned above.

Quote from: markorock37 on May 10, 2013, 01:21:20 PM
Transformer wires are correct. No voltage on P8 or P9 to ground unplugged.

We need to know the AC voltage at the wires that attach to P8 and P9.  Not DC voltage, and not at P8 or P9.
Disconnect the brown and brown/white wires from P8 and P9, connect your meter to the wires.
What is the AC voltage from brown to brown/white wire?  AC volts from brown wire to chassis ground?  AC volts from brown/white wire to chassis ground?

  There is no schematic in the attachment.

Quote from: Roly on May 09, 2013, 10:38:47 PM
Isolate the fan rectifier, D8-D11, and retest voltages, particularly P8 (TP5).

I think you mean D108-D111, also C116.

But before this, check what Enzo asked in reply #17.