To clear up a couple more design/operation issues:
input 1 is for ch.A use only
input 2 is for ch.A or B
So that should explain some of your questions about your tests
(http://www.award-session.com/pdfs/Award-Session%20History0026.pdf).

[On a side note, it irks me that they have called the clean channel "B".  This is so non-standard, I have to keep reminding myself B=clean here   :grr]

Now, 2 issues you mentioned previously.  You said clean channel was quite weak and required adding in from dist. channel to get level.
  This does not seem right and is possibly a defect that has been overlooked.  Using ch2 input, switch set to clean, how far up do you have to bring the volume to get decent level (without adding anything from dist. channel) ?
  The other thing you mentioned was a bit of distortion at the trailing edge of the note as it fades.  Maybe a cross-over distortion issue.

  The center position of the switch is where it must be set when using an external footswitch.
See pg.5 of schematic.  They call it "off", but it looks to me that when set in centre, with no external footswitch, everything should work.

Quote from: Peter Blair on January 24, 2015, 03:08:51 PM
I found these at "Just Radios". According to their product information these look (to the untrained eye) like they will fill the bill. They are available in the values that I need, and are very reasonably priced. Would you please render your opinion, and/or make me aware of other options or even a recommendation.

http://www.justradios.com/DMEcapacitors.html

Just Radios are an excellent company and you won't go wrong with them.

  In case you have a 300W bulb in your limiter because of the infamous video on youtube, please see Roly's discussion of limiter bulbs here:
http://www.ssguitar.com/index.php?topic=3636.msg28236#msg28236

  They have 2 versions on the schematic page:   http://www.award-session.com/award-session_manuals.html
If it is the '81-88 version, the headphone or ext. spkr jacks could cause that kind of problem if dirty/oxidized.
  If yours has those jacks, try to work some cleaner into them, or even just give them some exercise by plugging in and out of them (with power off) several times.

  The only thing immediately jumping out at me right now is that the volume pot wiper is drawn going straight to ground.

  Sure you can, and great deal!
You probably want to stay on the clean channel, higher master settings and lower gain settings.
  If it has some kind of crazy mid scooped metal eq'ing, stick an EQ pedal in front of it.

  Dual bananas are also fairly expensive.
Agree with Roly, XLR are a good option for carrying high current.
There are also 1/4" jacks with 2 tip contacts which helps, but they are not very common.

Early version schem:  http://www.drtube.com/schematics/marshall/5210-iss5.gif
Later version ('88):  http://www.drtube.com/schematics/marshall/5210-iss3.gif

Roly, you omitted at which step he should remove the short from FX return.  I'm guessing at the end of step #1 ?

  Thanks for posting that. 
Early on they had too small of a fuse in the F2 spot for the 5V supply.  It's the soldered in picofuse.  They had a T500mA in there and then they changed to a T1A.  It runs right around 500mA and would sometimes blow from turn on surge or high line voltage.  I fixed a couple using T750mA and never had a problem after.  That was before they updated to T1A, which is probably and easier value to find.
  No idea if that is a problem with yours, just thought I'd mention it here.

  Does it respond it you give it a whack when it is acting up?  Sometimes bad solder connections will only show up with prolonged heat.
  Also, a heatgun or hair dryer can help find heat related problems.
And if it has an effects loop, plug into the return after the problem occurs.  If the sound does not improve, then you have isolated it to the power amp or power supply.
What is the exact model/chassis number ?

  If the preamp has IC's, they will typically run on a split supply of approx. +/-15V.
It will often be derived from the main supplies, but the voltage dropping may be done either at the main supply or on the preamp board.
Seeing as we are completely blind about what this amp even is (not a common brand or model), some pictures would definitely help.
  As you did not have fuses blowing, and there is no DC on the output, you are probably ok now to connect the speaker and check for sound.
Does the amp have an effects loop (send and return jacks) ?

  For starters, the speaker should not be connected until you verify there is no DC at the amp output.
  With the speaker disconnected, check the amps output leads.  The - lead is often grounded so don't worry if you have continuity to chassis on the - wire.
  The + lead should not give continuity to ground.
Before connecting the speaker, when you turn the amp on measure for DC volts between the leads that go to the speaker.  There should not be any substantial DC there, maybe up to 50 millivolts.

Quote from: txflood on December 19, 2014, 11:12:13 AMThanks for this tip. I did get the specs from Ashdown now on the OPT and I'm guessing that it is bad as the drawing shows 8K ohms resistance on the primary windings. I am measuring a little less than 600 ohms.

Wouldn't this low primary resistance explain R76 burning up feeding the CT of the OPT?

The 8K figure is impedance, not resistance.  Impedance is an AC only spec. and we can't measure it with a normal type meter.  We can measure DC resistance but it will give a much lower measurement.  Your 600ohm resistance reading does not seem low at all, some amps OT primaries measure even lower.
R76 does not feed the CT.  Rather it feeds everything after the CT and the fact it is burning up implies the problem could be anything other than the output transformer.