I'm calling it fixed.
With the assist from TEch 21 Support , and a couple of emails.

From Tech 21:
  <<Be aware the Power Engine 60 utilizes a ground independent transformer, which may pick up hum from the auto-switching power supply. Therefore, the XLR input of the Power Engine 60should be grounded. You can make your own grounding plug by modifying a male XLR connector by soldering Pin 1 to Pin 3 and inserting into the XLR input of the Power Engine 60 per the diagram below. NOTE: If you're not into soldering, a Tech 21 grounding plug is avail-able for purchase. Please see our website Accessories page for details>>

I found the original manual, Celestion amp handle tag and the grounding XLR plug in a zip-lock bag from the original purchaser.

The PE amp is now as quiet as could be expected from any amp/effects combination.

It's done and on the slight chance that someone else has this issue, this post will turn up in a search and be of assistance.

Now onto my Yamaha G50-112ii    :lmao:

phatt,
  All this is with completed connections all around.
I just reconnected the chassis in the cabinet and speaker.
With nothing plugged in there was a slight hum with the gain cranked. When I backed the gain down a bit, 15-20%, it was close to silent.  I set up my guitar/preamp volume down on the preamp, and then plugged the output 1/4" connection into the power engine. The hum was significant, as I had remembered it.

I tried some balanced 1/4" patch cords in that same connection and it was no worse  and no better.

What I did notice was that any slight nudge on the 1/4" connection jack, produced a change, a reduction/increase as I moved it ever so slightly.
I'm going to call this a "Faulty Jack"  or  "Failing Solder Point" at this point.  The PC board shows no signs of repair or replacement. All looks pristine.

I'm going to desolder & remove the jack and check it's integrity at the connections plus and faults to ground. It has to be this easy. The amp on the XLR input works flawlessly.

I'll update the post as I discover more.


Dez

I searched (googled) the issue and found https://www.ssguitar.com/index.php?topic=4118.0

So I bought a PE60 for a very nice price (red flag) that has a hum on the 1/4" input only. I've been using it with an BOSS ME-80 with success taking the mono out into a direct box and then into the lo-Z input on the amp.
  So silly me, I want to fix the hum. The amp works great in all other respects.  The amp is dead quiet when nothing is plugged in. Once a 1/4 " mono plug  is inserted, theres a hum, similar to tapping the hot/tip an open jack.  Using the xlr input is quiet as well.

  As an avid electronic enthusiast, I have built 3 fairly complex amps , recapped and modded my SF Bassman, with rewarding success. I have no scope at this point.



I benched the chassis to look for a blessed "easy fix". It didn't happen. What I did find on the 1/4" input jack was that is a "marshall" insulated type but appears to be a stereo jack. It's PC mounted and has 6 solder lugs into the board. The 2 closest to the chassis face have traces, the middle 2 have traces, and the last 2 go through the board but do not appear to have traces. I know it could be a multi-layer board but honestly looks single layer.  (I stopped myself from starting a big trouble shooting session because it was 11:45PM. I'll put fresh eyes on it in the AM.

  Could it be that the input is wired for a balanced  1/4" input? And that using a standard mono guitar jack is fouling the ground on the amp? I'm looking for a schematic, and will find the manual in my paper pile.
The solder points look great but I'll tap them out a bit and check them with a meter to verify what I can.


From the manual
<<1/4" INPUT (*FOR INSTRUMENTS ONLY*)
Accepts 1/4" output of your pre-amp/processor or amplifier. This specialized input
features an isolation transformer to eliminate ground loops when using the Power
Engine 60 in conjunction with an amplifier. Be aware that this transformer loads down
passive guitar inputs. If you would like to plug your guitar directly into the Power Engine
60, either use an active guitar or any buffered type of effect pedal (Boss®, Ibanez®,
Tech 21, etc.) in bypass mode in order to drive the low input impedance of the amplifier.
*NOTE: DO NOT PLUG THE SPEAKER OUTPUT OF AN AMP INTO THIS
INPUT. Doing so may result in severe damage to the unit or your amp or both>>

Tomorrow is another day

Dez
NYC

I understand the point on lube creating a coating. I was taken by the "Cleaner" part of the label. Since the condition has been remedied, and the amp will get some use and stored in a nicer environment, I could shoot a blast of electrical cleaner, not a lot, but perhaps to clear off and residuals.
I was going to buy some Deoxit online and the supplier couldn't tell me which of his products would be best suited for my needs, I lieu of his customer service, I went to radio shack to get abused and spend too much but I had something in my hands immediately

Posted:
http://www.ssguitar.com/index.php?topic=3028.0

This is for  a 1990 era 400RB. There are schematics, layouts and manuals.
Should be here: https://drive.google.com/folderview?id=0B69gKOiNPWleb3g2U1hQVVBJZ1U&usp=sharing

I've gotten a response from G-K sales and IT coordinator requesting a serial number which I sent back already. I think I'll see some .pdf's from this. I'll host them as needed.
Meanwhile, I took a spray can of cleaner/lubricant and hit all the inputs and outputs, the send and return as well. Bam !! She's back online.
So I'm going to call it a little moisture and unuse, plus storage in a basement area, creating light to moderate corrosion on any or all of the jacks.
Its been idling for 20 minutes and the top is cool to the touch.

Beer is in order.

Gary

I will post the schematic as soon as it arrives.

Very nice page Roly. I've sent off an email to G-K. I have a bulb limiter from firing up my recent amp project.

Dez

First, Hello to everyone. Its my first post. I have a couple of SS amps, My Tech 21 TM-60, an older Yamaha G-112, An even older Peavey Renown 2-12, a previous and deceased and missed, GK-SEL-2100 (RIP, sniff)
  Somehow I've wound up with my sons RB400, which I took out to a BBQ/jam over the weekend. I set up and powered on but there was no sound. Pilot light lit, speaker plugged in, (swapped cable JIC), but no sound.
  As I inspected the head for any obvious problems, the top of the amp was very warm (not hot) to the touch, even after only a short time. The heat sink was also fairly warm but not hot, considering the under 2 minute run time.
  I traced back the amp usage over the last 3 months and I took it out one other time to power a floor monitor.  The monitor didn't work and I blamed it on the sound guy or the send cable. I'll bet the amp was failing then also.
  Yesterday I got to ask my son if he'd had any problem and he didn't recall, BUT, (big BUTT), there might have been one time last year he was running some music through the amp for a party and there were "Sprinkles" and he covered the amp with a plastic tarp. Possible red flag there I think.
  What might be the initial trouble shooting points on this amp? Output transistors, power supply, (amp lights up). Is there a fuse on the output?
I'm going to rummage up an schematic and get prepared in the mean time.
I've got above beginner skills, not expert. I've built a 2-6L6 tube amp from scratch, (no kit, sourced parts), but the well of knowledge is quite deep and I'm just dipping a ladle in.

Thanks for any and all info,
Dez
NYC